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Thermodynamic assessment and experimental investigation on the formation of titanium hydride (TiH2) from the reaction between titanium tetrachloride (TiCl4) gas and magnesium hydride (MgH2) powder were carried out under hydrogen atmosphere. In this new method, the production of TiH2 powder at low temperature was investigated, which can be used for further dehydrogenation process to produce low-cost Ti powder. In this work, the effects of temperature, time, amount of titanium trifluoride (TiF3) as a catalyst, and ball-milling time of the MgH2 on the formation of TiH2 were investigated. The phase transformations and evolution of the morphology of the powders with an increase in time and temperature were studied by x-ray diffraction and scanning electron microscopy, respectively. The results of the reaction at 400 °C for 10 h indicated that producing TiH2 from the reduction of TiCl4 with MgH2 at low temperature was feasible and has a significant potential for the low-cost synthesis method of TiH2 for Ti powder production.

In this work, the novel utilisation of customised double- and triple-tail sodium bis(3,5,5-trimethyl-1-hexyl) sulphosuccinate (AOT4) and sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-silphonate (TC14) surfactants to assist the direct graphene oxide (GO) synthesis via electrochemical exfoliation utilising dimethylacetamide (DMAc) as a solvent were investigated. The synthesised DMAc-based GO and titanium dioxide (TiO2) nanoparticles were then used to fabricate polyvinylidene fluoride (PVDF)-based nanofiltration (NF) membranes by the non-solvent-induced phase separation method. The incorporation of GO and TiO2 as hydrophilic nanoparticles were to enhance membrane hydrophilicity. The utilisation of higher surfactants’ tail number obviously alters the fabricated membrane’s morphology which further affects its performance for dye rejection and antifouling ability. Higher surfactants’ tail number resulted in higher oxidation process which then provided more interaction between the GO and PVDF. Based on the dead-end cell measurement, PVDF/TC14-GO/TiO2 presented a slightly higher dye rejection efficiency of 92.61% as compared to PVDF/AOT4-GO/TiO2 membrane (92.39%). However, PVDF/TC14-GO/TiO2 possessed three times higher water permeability (48.968 L/m2 h MPa) than PVDF/AOT4-GO/TiO2 (16.533 L/m2 h MPa) and also higher hydrophilicity as presented by lower contact angle (65.4 ± 0.17°). This confirmed that higher surfactants’ tail number improved the fabricated membrane’s performance. Both fabricated membranes also exhibited high flux recovery ratio (FRR) ( $$>$$ 100%) which indicated better antifouling properties.

This study explored the potential of In2O3/ZrO2 catalyst for direct CO2 hydrogenation to methanol. Despite the excellent properties proven by density functional theory (DFT) studies, the experimental works on this catalyst are still very limited. In this study, In2O3/ZrO2 catalysts were synthesized via wetness impregnation (In2O3/ZrO2(WI)), citric acid-based sol-gel method (In2O3/ZrO2(SG)) and deposition-precipitation assisted by urea hydrolysis (In2O3/ZrO2(UH)). Results indicated the impressive effect of preparation method on the catalytic activity where In2O3/ZrO2(SG) presented superior catalytic performance, followed by In2O3/ZrO2(UH) and In2O3/ZrO2(WI), with the CO2 conversion of 16.23%, methanol selectivity of 94.39% and STY of 0.95 gmethanol/gcat·h. To unravel the structure-function relationship, several characterization techniques including XRD, HR-TEM, SEM-EDX, H2-TPR, CO2-TPD, N2 adsorption-desorption isotherm and XPS were implemented to analyze the developed catalysts. The analyses indicated that the excellent performance of In2O3/ZrO2 (SG) was due to its smaller crystallite size, strong metal-support interaction, high reducibility and high concentration of basic sites and oxygen vacancies on the catalyst surface. Time-on-stream stability test showed that In2O3/ZrO2 (SG) catalyst could sustain its high activity and selectivity within 100 h, signifying the high potential of this catalyst for direct hydrogenation of CO2 to methanol with minimum side reactions and deactivation.

Several multi-walled carbon nanotubes supported Ni-Ce catalysts were synthesized, and their performance in carbon dioxide reforming of methane (CDRM) for syngas production was evaluated. The attachment of Ni-Ce nanoparticles to the functionalized carbon nanotube (fCNT) support was carried out using four synthesis routes, i.e., impregnation (I), sol-gel (S), co-precipitation (C), and hydrothermal (H) methods. Results indicated that synthesis method influences the properties of the NiCe/fCNT catalysts in terms of homogeneity of metal dispersion, size of crystallites, and metal-support interaction. The activity of the catalysts followed the order of NiCe/fCNT(H) > NiCe/fCNT(S) > NiCe/fCNT(C) > NiCe/fCNT(I). The NiCe/fCNT(H) catalyst exhibited the highest catalytic activity with CH4 and CO2 conversions of 92 and 96%, respectively, and resulted in syngas product with consistent H2/CO ratio of 0.91 at reaction temperature of 800 °C without notable deactivation up to 30 h of reaction. Moreover, the growth of carbon on the spent catalyst was only 2% with deposition rate of 4.08 mg/gcat·h; this was plausibly due to the well-dispersed distribution of nanoparticles on fCNT surface and abundant presence of oxygenated groups on the catalyst surface.

Photocatalytic CO2 reduction is a revolutionary approach to solve imminent energy and environmental issues by replicating the ingenuity of nature. The past decade has witnessed an impetus in the rise of two-dimensional (2D) structure materials as advanced nanomaterials to boost photocatalytic activities. In particular, the use of 2D carbon-based materials is deemed as highly favorable, not only as a green material choice, but also due to their exceptional physicochemical and electrical properties. This Review article presents a diverse range of alterations and compositions derived from 2D carbon-based nanomaterials, mainly graphene and graphitic carbon nitride (g-C3 N4 ), which have remarkably ameliorated the photocatalytic CO2 performance. Herein, the rational design of the photocatalyst systems with consideration of the aspect of dimensionality and the resultant heterostructures at the interface are systematically analyzed to elucidate an insightful perspective on this pacey subject. Finally, a conclusion and outlook on the limitations and prospects of the cutting-edge research field are highlighted.

The photocatalytic conversion of CO2 to energy-rich CH4 solar fuel is an ideal strategy for future energy generation as it can resolve global warming and the imminent energy crisis concurrently. Ho...

Titanium hydride (TiH2) is one of the basic materials for titanium (Ti) powder metallurgy. A novel method was proposed to produce TiH2 from the reduction of titanium tetrachloride (TiCl4) with magnesium hydride (MgH2) in the hydrogen (H2) atmosphere. The primary approach of this process is to produce TiH2 at a low-temperature range through an efficient and energy-saving process for further titanium powder production. In this study, the thermodynamic assessment and technoeconomic analysis of the process were investigated. The results show that the formation of TiH2 is feasible at low temperatures, and the molar ratio between TiCl4 and metal hydride as a reductant material has a critical role in its formation. Moreover, it was found that the yield of TiH2 is slightly higher when CaH2 is used as a reductant agent. The calculated equilibrium composition diagrams show that when the molar ratio between TiCl4 and metal hydrides is greater than the stoichiometric amount, the TiCl3 phase also forms. With a further increase in this ratio to greater than 4, no TiH2 was formed, and TiCl3 was the dominant product. Furthermore, the technoeconomic study revealed that the highest return on investment was achieved for the production scale of 5 t/batch of Ti powder production, with a payback time of 2.54 years. The analysis shows that the application of metal hydrides for TiH2 production from TiCl4 is technically feasible and economically viable.

This work is scrutinizing the development of metallized biochar as a low-cost bio-sorbent for low temperature CO2 capture with high adsorption capacity. Accordingly, single-step pyrolysis process was carried out in order to synthesize biochar from rambutan peel (RP) at different temperatures. The biochar product was then subjected to wet impregnation with several magnesium salts including magnesium nitrate, magnesium sulphate, magnesium chloride and magnesium acetate which then subsequently heat-treated with N2. The impregnation of magnesium into the biochar structure improved the CO2 capture performance in the sequence of magnesium nitrate > magnesium sulphate > magnesium chloride > magnesium acetate. There is an enhancement in CO2 adsorption capacity of metallized biochar (76.80 mg g−1) compare with pristine biochar (68.74 mg g−1). It can be justified by the synergetic influences of physicochemical characteristics. Gas selectivity study verified the high affinity of biochar for CO2 capture compared with other gases such as air, methane, and nitrogen. This investigation also revealed a stable performance of the metallized biochar in 25 cycles of CO2 adsorption and desorption. Avrami kinetic model accurately predicted the dynamic CO2 adsorption performance for pristine and metallized biochar.

In this present study, a green modified co-precipitation technique has been employed for the synthesis of green ZnO products (Z-ZnO, A-ZnO and P-ZnO) using plant waste extracts of corn (Zea mays) husk, jackfruit (Artocarpus heterophyllus) peel and pomegranate (Punica granatum) peel as well as simultaneously without plant extract (C-ZnO), respectively. All synthesized photocatalysts were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET) surface area analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The phytochemical screening analyses showed that the P-ZnO had the highest polyphenol and flavonoid contents. Under visible light irradiation, all green ZnO products demonstrated excellent antibacterial activities against Enterococcus faecalis (E. faecalis) bacteria compared to C-ZnO and commercial ZnO. P-ZnO had the highest photocatalytic antibacterial performance among all green ZnO products. Moreover, the bacterial regrowth examinations were carried out to determine the practicality of this treatment. The FTIR analysis also revealed the damage of bacterial membrane through cellular substance alteration. The radical scavenger experiments presented that hydrogen peroxide (H2O2) played a significant role in photocatalytic antibacterial of E. faecalis. The synthesized P-ZnO also exhibited the highest antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenger compared to other tested ZnO.

The unique properties of mesostructured cellular foam (MCF) silica such as, large pore size, continuous three-dimensional (3D) pore system and hydrothermal robust materialallow favorable conditions for incorporating active sites to produce modified MCF silica as catalysts, biocatalysts and adsorbents. Recently, the modified MCF silicas were reported to be efficient catalysts for the hydrogenation of phenylacetylene, heck coupling reaction of arylboronic acid, etc. Biocatalysts derived from modified MCF silicas were found to be a potential to convert glucose to gluconic acid, hydrolysis of N-benzoyl-DLarginine-p-nitroanilide (BAPNA) and casein, transesterification of racemic 1 phenyl- ethanol and hydrolytic, etc. Several separation processes such as CO2 capture and adsorption of L-tryptophan, lysozyme and bovine serum were sucessfully conducted using adsorbents derived from modified MCF silicas. This paper reviews the synthesis of the MCF silica material and the incorporation of active sites or immobilization of enzymes in the MCF silica material. Additionally, a detailed understanding of the characterization of the modified MCF silicas, which includes pore size, active sites/enzymes sizes, amount of active sites/enzymes bound with the MCF silica, was also discussed to obtain their potentialities as catalysts, biocatalysts and adsorbents. The review also describes recent progress on the applications of the MCF silica.

Novel ZnO/Nd-BiOBr composites were facilely synthesized via a surfactant-free chemical approach. The ZnO nanoflakes were loaded on the surface of Nd-BiOBr nanosheets with intimately contact. The synthesized ZnO/Nd-BiOBr demonstrated significantly higher visible light photocatalytic degradation of phenol compared to those of ZnO, BiOBr and Nd-BiOBr. The enhanced photocatalytic activity of ZnO/Nd-BiOBr was attributed to the effective separation of photogenerated electron-hole in the heterojunction structure as proven via the photoluminescence spectra. In addition, the ZnO/Nd-BiOBr showed good stability in phenol degradation for four irradiation cycles. The radical trapping experiments indicated that the hydroxyl radicals played key role in the photodegradation process.

In this paper, screening study in regards to preparation of functionalized multi-walled carbon nanotubes (FMWNT)-supported bi-metallic catalyst is discussed. Functional groups such as hydroxyl and carboxylic acid are introduced on multi-walled carbon nanotubes (MWCNT) surface using acid treatment method with the aid of probe-type ultrasonication. It is done by varying the concentration of nitric acid (HNO3) and sulphuric acid (H2SO4), acid volume ratio and treatment duration. Catalysts with different ratios of cerium and nickel nanoparticles which are either loaded inside or outside of MWCNT were prepared via ultrasonic-assisted co-precipitation method (NiCe/CNT). This is done to study the effect of cerium loadings. The characterization of the FMWNT and catalysts are carried out using transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and Raman spectroscopy. The results showed that the treatment in concentrated HNO3/H2SO4 with volume ratio of 3:1 for 8 h was the most suitable condition to generate large amount of surface oxygen group with minimal defects. The observations for each used condition were discussed thoroughly. Decoration of MWCNT with different metal loadings resulted in different distribution and dispersion of metal on nanotubes surface.

This research was performed to evaluate the mechanical and thermal properties of sugar palm fiber (SPF)- and kenaf fiber (KF)-reinforced polypropylene (PP) composites. Sugar palm/kenaf was successfully treated by benzoylation treatment. The hybridized bio-composites (PP/SPF/KF) were fabricated with overall 10 weight percentage (wt%) relatively with three different fibers ratios between sugar palm-treated and kenaf-treated (7:3, 5:5, 3:7) and vice versa. The investigations of thermal stability were then carried out by using diffraction scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The result of a flammability test showed that the treated hybrid composite (PP/SPF/KF) was the specimen that exhibited the best flammability properties, having the lowest average burning rate of 28 mm/min. The stiffness storage modulus (E’), loss modulus (E”), and damping factor (Tan δ) were examined by using dynamic mechanical analysis (DMA). The hybrid composite with the best ratio (PP/SPF/KF), T-SP5K5, showed a loss modulus (E”) of 86.2 MPa and a damping factor of 0.058. In addition, thermomechanical analysis (TMA) of the studies of the dimension coefficient (µm) against temperature were successfully recorded, with T-SP5K5 achieving the highest dimensional coefficient of 30.11 µm at 105 °C.

Activation is commonly used to improve the surface and porosity of different kinds of carbon nanomaterials: activated carbon, carbon nanotubes, graphene, and carbon black. In this study, both physical and chemical activations are applied to graphene oxide by using CO2 and KOH-based approaches, respectively. The structural and the chemical properties of the prepared activated graphene are deeply characterized by means of scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry and nitrogen adsorption. Temperature activation is shown to be a key parameter leading to enhanced CO2 adsorption capacity of the graphene oxide-based materials. The specific surface area is increased from 219.3 m2 g−1 for starting graphene oxide to 762.5 and 1060.5 m2 g−1 after physical and chemical activation, respectively. The performance of CO2 adsorption is gradually enhanced with the activation temperature for both approaches: for the best performances of a factor of 6.5 and 9 for physical and chemical activation, respectively. The measured CO2 capacities are of 27.2 mg g−1 and 38.9 mg g−1 for the physically and chemically activated graphene, respectively, at 25 °C and 1 bar.

Eco-friendly materials are needed in developing countries; therefore researchers are currently focused on material selection and developing a new material that will increase the environmental value of products. Numerous plant fibers have been reported as adding significant properties to the product materials, such as fast-growing and lightweight, low-cost, better mechanical properties, and requiring low production energy consumption, which can be used in structural and critical applications. Polypropylene (PP) is one of the most commonly used polymers in various applications. Alternative materials to the current synthetic fillers used in PP composites need to be identified to promote greener and safer materials in these industries. The introduction of natural fillers in PP composites was seen as one of the brightest solutions toward more environmentally friendly materials. However, the inclusion of individual natural fiber in PP composites does not significantly improve the strength of the composites. The use of coupling agents to modify the PP composites can enhance the fiber–matrix interfacial bonding, thus enhancing the strength of the natural fiber/PP composites. In addition, surface modification applied to the natural fiber using different types of treatments helps improve the strength of the composites. This review discusses several factors that affect the mechanical properties of natural fiber/PP composites, such as the effect of coupling agents, chemical treatments, and different percentages of fiber loading, as a reference for future studies in respective areas.

Carbon dioxide (CO2) capture by using calcium (Ca)-based adsorbents derived from natural wastes has attracted the attentions of many researchers nowadays. Utilization of these natural materials in CO2 capture is able to reduce the cost of the adsorbents and favor to the production cost. In this research, CaO-based adsorbents that derived from natural clam (Meretrix meretrix) shells and cockle (Anadara granosa) shells were modified for their properties through ethanol-water hydration treatment and studied for their performance in CO2 capture. The effect of ethanol concentrations in ethanol-water hydration treatment was investigated in order to identify the optimum ethanol concentration to achieve desired adsorbent properties and best performance in CO2 capture. Ethanol was found to have a role in expanding the pore structure of CaO sorbents in this study. Treated CaO-based adsorbents derived from shells were found to have a higher surface area and pore volume as compared to untreated samples. CaO-based adsorbent derived from clam shells and cockle shells treated with ethanol were found to achieve higher CO2 adsorption capacity at 13.72 mmol CO2 / g adsorbent and 16.57 mmol CO2 / g adsorbent, respectively, as compared to untreated clam shells and cockle shells, which recorded CO2 adsorption capacity of 7.95 mmol CO2 / g adsorbent and 9.61 mmol CO2 / g adsorbent, respectively. This was corresponded to the higher surface area of the treated adsorbent samples, which promoted the CO2 adsorption activity.

This study deals with the development of alumina-supported cobalt (Co/Al2O3) catalysts with remarkable performance in dry reforming of methane (DRM) and least carbon deposition. The influence of Co content, calcination, and reduction temperatures on the physicochemical attributes and catalyst activity of the developed catalysts was extensively studied. For this purpose, several characterization techniques including ICP-MS, H2 pulse chemisorption, HRTEM, H2-TPR, N2 adsorption desorption, and TGA were implemented, and the properties of the developed catalysts were carefully analyzed. The impact of reaction temperature, feed gas ratio, and gas hourly space velocity (GHSV) on the reactants conversion and products yield was investigated. Use of 10%Co/Al2O3 catalyst, calcined at 500°C and reduced under H2 at 900°C in DRM reaction at 850°C, CH4/CO2 ratio of 1:1, and GHSV of 6 L.g−1.h−1 resulted in a remarkable catalytic activity and sustainable performance in long-term operation where great CO2 (96%) and CH4 (98%) conversions and high H2 (83%) and CO (91%) yields with a negligible carbon deposition (3 wt%) were attained in 100-h on-stream reaction. The good performance of the developed catalyst in DRM reaction was attributed to the small Co particle size with well-dispersion on the alumina support which increased the catalytic activity and also the strong metal-support interaction which inhibited any serious metal sintering and enhanced the catalyst stability.

This study investigated the coagulation performance of titanium tetrachloride (TiCl4) for leachate treatment and preparation of titanium oxide (TiO2) from generated sludge through calcination process at different temperatures and times. TiCl4 with chitosan as coagulant aid employed to perform coagulation process on Alor Ponhsu Landfill leachate. Further calcination process was done to synthesize TiO2 from produced sludge for photocatalytic applications. The studied factors included pH, TiCl4 dosage, and chitosan dosage. The results indicated that maximum reduction in suspended solids was 92.02% at pH 4, 1200 mg/L TiCl4, and 250 mg/L chitosan addition, and maximum reduction in chemical oxygen demand was 71.92% at experimental condition of 1200 mg/L TiCl4 and 500 mg/L chitosan with pH 10. The maximum and minimum band gaps of prepared TiO2 achieved at 3.35 eV and 2.75 eV, respectively. Morphology and phase analysis of prepared TiO2 characterized using scanning electron microscope (SEM) and X-ray diffraction (XRD). The XRD spectrums showed the anatase phase at lower calcination temperature and the rutile phase at elevated temperature. The photocatalysis activity of produced TiO2 investigated under UV irradiation and showed almost fast degradation similar to commercial TiO2. The results indicated that TiO2 powder was successfully prepared from generated sludge from TiCl4 coagulation for photocatalytic applications.

Titanium hydride (TiH2) uses as a raw material in powder metallurgy method to produce titanium powder. The novel method was introduced to synthesize TiH2 from reaction between titanium (Ⅳ) chloride (TiCl4) and magnesium hydride (MgH2). The critical step in synthesize of TiH2 in this method, is formation of titanium (Ш) chloride (TiCl3) during reactions in the system. The reaction between synthesized TiH2 powder and excess TiCl4 gas in the system can result in the formation of TiCl3. In this study, effect of nickel (Ni) metal and ammonium chloride (NH4Cl) as catalyst was investigated on formation of TiCl3 under hydrogen atmosphere. Statistical design of experiment (DOE) method was applied to examine the effect of catalyst at various conditions. The main including factors were reaction time, temperature and amount of catalyst. It was observed that change in the amount of Ni had the most significant effect on weight loss of TiH2. The results of DOE analysis showed that maximum weight loss reached at temperature of 250 °C, 120 minutes reaction time and 0.1 molar ratio of Ni/NH4Cl. Samples were characterized with X-Ray Diffraction analysis. The results confirmed that excess amount of TiCl4 in the system led to formation of TiH2 to TiCl3, which is not favourable in production of TiH2 powder.

Titanium metal can be obtained through low cost carbothermal reduction process with the end product of titanium oxycarboniterate (TiOxCyNz). Kinetic modeling is required to understand the carbothermal reduction reactions to control the process more effectively. The objective of this paper is to compare the theoretically predicted results with the experiment results of TiO2-Fe2O3 for three manipulated parameters and to model the kinetic mechanisms of reduction process using the shrinking core model. Synthetic anatase and hematite were mixed with carbon in order to study its carbothermal reduction kinetics reaction experimentally. Then, a shrinking core model was developed to determine the theoretical extent of reduction at different temperature (1150 and 1250 °C) when reactant gas diffused into the solid pellet sample. The model was simulated for two conditions, namely isothermal and non-isothermal reduction. It is assumed that the pellet has number of shells which would react uniformly and completely. This model was developed by applying physical and thermodynamics properties of elements/compounds involved in the reaction. It was observed that non-isothermal condition model has lower extent of reduction compared to isothermal condition. while the non-isothermal extent of reduction model is the closest to the experimental compared to the isothermal model. The extent of reduction predicted by the model deviated from experimental but still had similar trend of reduction. i.e., high reduction concomitant with high temperature and time.

Well-designed template free synthesis of one dimensional (1D) graphitic carbon nitride nanorods (g-CNR) coupled with two dimensional (2D) trimetallic CoAlLa-LDH to construct 1D/2D interface heterostructures with strong electrostatic interactions between positively charged 2D LDH sheets and negatively charged 1D g-CNR has been investigated. The lanthanum doped CoAlLa-LDH with unsaturated metal centers has increased reductive sites and oxygen vacancies that led to enhanced charge separation. The 1D g-CNR provides extra active reaction sites for the photocatalytic reaction and permit fast photogenerated charge carriers separation across the interface. The coupling of g-CNR and CoAlLa-LDH with excellent properties resulted in 1D/2D interface heterojunction with S-scheme mechanism for charge carrier transfer by maintaining and effectively utilizing useful charge carriers. The 1D/2D g-CNR/CoAlLa-LDH showed remarkable photocatalytic performance for CO2 reduction with H2O resulting in maximum CO and CH4 production of 17.85 and 14.66 µmole, respectively. The photocatalytic bireforming (BRM) of methane resulted in the production of syngas (CO/H2) with 12.32 and 5.96 µmole of CO and H2, respectively. The enhancement of photocatalytic activity attributed mainly due to the excellent interfacial contact of g-CNR with ternary metallic CoAlLa-LDH, thus resulting in better transfer and separation of photogenerated charge carriers due to the formation of S-scheme heterojunction. Additionally, the optimum g-CNR/CoAlLa-LDH nanocomposite acquired high photostability after consecutive experimental runs with no apparent variation. The spent catalyst showed no change in morphology, thus proving further good stability of the g-CNR/CoAlLa-LDH photocatalyst. The findings of this work would be beneficial to design template free heterojunction for photocatalytic CO2 reduction and other solar energy application.

Copper-based catalysts with different metal-oxide(s) composition were synthesized and applied in CO2 hydrogenation to methanol. The metal component(s) (Cu, Zn and/or Mn) were dispersed on high surface area SBA-15. Correlations between the adsorption properties of catalysts and the catalytic performances reveal that a catalyst with both strong hydrogenation strength and moderate CO2 adsorption strength is crucial for achieving high CO2 conversion. Additionally, the availability of metal-oxide(s) interfacial area greatly enhances methanol selectivity. An adequate balance between H2 and CO2 adsorptions as well as metal-oxide(s) interfacial area were responsible for the high catalytic activity achieved in this study.

Aluminum (Al)-doped titanium dioxide nanorod arrays (ATNs) were grown on fluorine-doped tin oxide-coated glass at different Al atomic concentrations ranging from 1 at.% to 5 at.% in a Schott bottle through single-step aqueous chemical growth for self-powered photoelectrochemical cell-type ultraviolet (UV) photosensor applications. X-ray diffraction patterns showed that the grown ATNs exhibited a crystalline rutile structure. The ATNs showed smaller crystallite size and average nanorod diameter and length compared with the undoped sample. The photocurrent measured from the fabricated UV photosensors improved to some extent with increasing Al-dopant concentration. Samples with 2 at.% Al showed the maximum photocurrent of 108.87 μA/cm2 at 0 V bias under UV irradiation (365 nm, 750 μW/cm2). The results show that high-performance UV photosensors can be fabricated and enhanced using ATNs easily prepared in a glass container.

A series of copper-catalysts, Cu-ZnO-MnO (CZM), supported on morphologically distinct siliceous porous carriers (SBA-15, MCF, KIT-6) were synthesized and applied in direct CO2 hydrogenation to methanol. The morphological impact of porous carriers on the formation and growth of copper crystallites and the molecular pore diffusion of the porous catalysts were investigated. Among the synthesized catalysts, KIT-6 supported catalyst (CZM/KIT-6) presented the most superior properties. The morphology of KIT-6 deterred mesopore plugging and favored the formation of small copper crystallites. CZM/KIT-6 also possessed greater resistance to copper crystallite growth and loss of copper surface area during reaction due to the pore-confining effect of the porous carrier and the larger inter-crystallites spacing among copper crystallites. The high effective diffusivity (catalyst pore-geometry dependent coefficient) of CO2 molecules in CZM/KIT-6 could indicate efficient transfer of reactant molecules to active sites and the removal of reaction products. The superior characteristics of CZM/KIT-6 contributed to the high CO2 conversion (8.2%) and high methanol production rate (105.3 mol/kgcat.h) at low reaction temperature (180 °C). The methanol selectivity attained was ≥99% in all the experiments.

In this work, custom-made triple-tail sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-silphonate (TC14) surfactant was used to assist exfoliation through electrochemical method for synthesis of graphene oxide (GO). A commercially available single-tail sodium dodecyl sulphate (SDS) surfactant was also utilised for comparison. Both synthesised GOs were reduced to produce reduced GO (rGO), which was fabricated into thin films through spray coating. The rGO thin film assisted by TC14 surfactant (TC14-rGO) with Pt nanoparticles was hybridised to improve electrical conductivity. The five different fabricated thin films were TC14-GO, TC14-rGO, SDS-rGO, Pt and TC14-rGO/Pt hybrid, which were used in dye-sensitised solar cells (DSSCs) as counter electrode (CE). Zinc oxide nanorods/titanium dioxide (ZnO NRs/TiO2 bilayer) was used as photoanode and fabricated through a simple sol–gel immersion and squeegee method. Based on solar simulator measurement, TC14-rGO/Pt hybrid CE thin film exhibited the highest energy conversion efficiency of approximately 0.044% with the Voc, Jsc and FF values of approximately 0.618 V, 0.163 mA/cm2 and 0.387, respectively, compared with other fabricated CE materials. The combination of TC14-rGO/Pt hybrid CE and ZnO NRs/TiO2 bilayer photoanode enhanced the DSSCs photovoltaic performance because of the high conductivity, low oxygen content, high quality and less agglomeration of thin rGO films as a result of improved exfoliation by triple-tail TC14 surfactant.

An improved dye-sensitized solar cell (DSC) of rutile-phased titanium dioxide (TiO2) electrode with increased power conversion efficiency was successfully fabricated. Rutile-phased TiO2 nanorods and nanoflowers were grown directly on fluorine-doped SnO2 (FTO) by simple aqueous chemical growth technique using one-step hydrothermal process. The solution was prepared by mixing hydrochloric acid, deionized water, and titanium butoxide used as precursor. In the preparation of DSC, both TiO2 nanorods and nanoflowers, platinum (Pt), ruthenium dye N719, and DPMII electrolyte were used as photoelectrode, counter electrode, dye solution, and liquid electrolyte, respectively. The prepared rutile-phased TiO2 nanorods and nanoflowers samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSCs were fabricated based on the rutile-phased titanium dioxide nanorod and nanoflower photoelectrodes. For their energy conversion efficiency, I-V characteristics and electrochemical impedance spectroscopy were studied. We also investigated the effect of cetyltrimethylammonium bromide (CTAB) reaction times 2, 5, and 10 h in the preparation of rutile-phased TiO2 nanoflowers for DSC. CTAB is one of the capping agents that cover the refine surface of nanoparticles and prevent them from coagulation or aggregation. In our final result, the combination of rutile-phased TiO2 nanorod- and nanoflower-based DSCs showed best efficiency at approximately 3.11% due to its good electron transport of TiO2 nanorods and increased surface area by the TiO2 nanoflowers that had increased dye absorption.

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted.

The role of hyperbranched surfactant, namely, sodium 1,4-bis (neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14), in the synthesis and stabilisation of reduced graphene oxide (rGO) as counter electrode (CE) thin film was investigated for dye-sensitised solar cell (DSSCs) application. The energy conversion efficiency ( η ) of CE-based rGO from TC14 (TC14-rGO) was 0.0266%, with a short current density, open circuit voltage and fill factor of 0.222 mA/cm2, 0.697 V and 14.15, respectively. The efficiency of the surfactant was two times higher than that of CE-based rGO from single-tail sodium dodecyl sulphate surfactant. Graphene oxide (GO) was initially synthesised by electrochemical exfoliation method. Hydrazine hydrate was subsequently used in the production of rGO through chemical reduction process. Spraying deposition method was used to transfer GO and rGO solutions and fabricate GO and rGO CE thin films. A novel combination of hydrothermal growth and squeegee method in the synthesis and production of mixed-phase titanium dioxide (TiO2) nanostructures as photoanode was selected due to its simple and low-cost method. Rutile TiO2 nanorods and anatase TiO2 nanoparticles are essential in electron transfer process and dye adsorption, respectively. Therefore, these combinations resulted in improved photocatalytic activity and η of dye-sensitised solar cells when TC14-rGO was used.

The world is currently facing the challenges of global warming and climate change. Numerous efforts have been taken to mitigate CO2 emission, among which is the use of solid sorbents for CO2 capture. In this work, Li4SiO4 was synthesised via a sol–gel method using lithium nitrate (LiNO3) and tetraethylorthosilicate (SiC8H20O4) as precursors. A parametric study of Li:Si molar ratio (1-5), calcination temperature (600–800 °C) and calcination time (1–8 h) were conducted during sorbent synthesis. Calcination temperature (700–800 °C) and carbonation temperature (500–700 °C) during CO2 sorption activity were also varied to confirm the optimum operating temperature. Sorbent with the highest CO2 sorption capacity was finally introduced to several cyclic tests to study the durability of the sorbent through 10 cycles of CO2 sorption–desorption test. The results showed that the calcination temperature of 800 °C and carbonation temperature of 700 °C were the best operating temperatures, with CO2 sorption capacity of 7.95 mmol CO2∙(g sorbent)− 1 (93% of the theoretical yield). Throughout the ten cyclic processes, CO2 sorption capacity of the sorbent had dropped approximately 16.2% from the first to the tenth cycle, which was a reasonable decline. Thus, it was concluded that Li4SiO4 is a potential CO2 solid sorbent for high temperature CO2 capture activity.

While sulphur dioxide (SO2) is known for its toxicity, numerous effective countermeasures were innovated to alleviate its hazards towards the environment. In particular, catalytic reduction is favoured for its potential in converting SO2 into harmless, yet marketable product, such as elemental sulphur. Therefore, current review summarises the critical findings in catalytic SO2 reduction, emphasising on both dry- and wet-based technology. As for the dry-based technology, knowledge related to SO2 reduction over metal-, rare earth- and carbon-based catalysts are summarised. Significantly, both the reduction mechanisms and important criteria for efficient SO2 reduction are elucidated too. Meanwhile, the wet-based SO2 reduction are typically conducted in reactive liquid medium, such as metal complexes, ionic liquids and organic solvents. Therefore, the applications of the aforesaid liquid mediums are discussed thoroughly in the similar manner to dry-technology. Additionally, the pros and cons of each type of catalyst are also presented to provide valuable insights to the pertinent researchers. Finally, some overlooked aspects in both dry- and wet-based SO2 reduction are identified, with potential solutions given too. With these insights, current review is anticipated to contribute towards practicality improvement of catalytic SO2 reduction, which in turn, protects the environment from SO2 pollution.

With the gradual rise in atmospheric carbon dioxide brought about by human activities and industry effluents, research has now been geared toward carbon capture and storage. To achieve high carbon dioxide adsorption capacity, development of nanomaterials with optimized properties has been attracting growing interest for more than ten years already. Such multi-parameter investigations require a complex and rigorous analysis in order to compare the different developed adsorbents and improve their performances. In this review, we propose a state-of-the-art approach related to the four most studied nanostructured adsorbents for carbon dioxide capture: graphene, carbon nanotubes, zeolite, and metal organic frameworks. The capture processes and the nanomaterials of interest were described as well as the modifications applied to improve the efficiency of carbon dioxide capture. The present unprecedented analysis allows to correlate the nanomaterial properties, especially surface area and pore volume, to the CO2 adsorption capacity. The results reveal that contrary the popular belief, the CO2 capture improvement is not solely liable on the high surface area and the high pore volume of the nanosorbents. This outcome may be useful in the course of improvement of nanostructured materials for CO2 capture for future technologies.

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil–5 (ZSM-5), TiO2, and Al2O3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir–Hinshelwood or Eley–Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH3 catalyst are suggested.

Combining adsorptive activated carbon and catalytic oxidative cerium oxide, an adsorptive catalyst could be synthesized. Cerium oxide impregnated on activated carbon had been utilized in various gas pollutant removal technologies. In this study, impregnation of cerium oxide and sodium hydroxide on palm shell activated carbon (PSAC) was attempted to produce an adsorbent for H2S removal from biogas produced in palm oil industry. Effects of preparation parameters of CeO2/NaOH/PSAC towards H2S removal were successfully studied. The studied parameters were impregnation time, cerium amount, NaOH concentration, calcination temperature and calcination time. From the study, it was found that every parameter can be optimized because there was a value of the parameter that resulted in a maximum adsorption capacity. The optimum preparation parameters of CeO2/NaOH/PSAC were found to be 1.5 h impregnation time, 5% cerium, 1.0 M NaOH, 400 °C calcination temperature and 3 h calcination time. Selected adsorbents were characterized in order to further understand adsorbent properties and characteristics of the reaction.

Carbon dioxide reforming of methane was studied over Co/MgO catalyst which was prepared by using the direct sol–gel method with different Co loadings. The performance of Co/MgO catalyst was thoroughly investigated over methane (CH4) and carbon dioxide (CO2) conversions, CO and H2 selectivity, syngas ratio (H2:CO) and the rate of carbon deposition. The rate of carbon deposition of Co/MgO catalyst decreased with the lower Co content, which resulted in the formation of small metal crystal size and well distribution. The rate of carbon deposition increased from 0.0016 to 0.2227 gc/gcat h as the Co loadings of Co/MgO catalyst also increased from 10 to 25 mol%. High Co loading formed a weak interaction and larger particles size that promoted the carbon deposition on Co/MgO catalyst during the reaction. The Co/MgO catalyst with 10 mol% of Co loading posed the small particle sizes, which resulted in high CH4 and CO2 conversions of 80 and 86%, respectively, along with the lowest rate of carbon deposition after a 50 h reaction time stream, which was enhanced via strong metal support interaction.

The direct CO2 hydrogenation to methanol is an attractive route to actively remove CO2 and to promote sustainable development. Herein, the performance of Cu-Zn-Mn catalyst supported on mesoporous silica KIT-6 (hereafter, CZM/KIT-6) for methanol synthesis by direct CO2 hydrogenation reaction was investigated by varying the process parameters, which included the weight-hourly space velocity, reaction temperature and reaction pressure. The CO2 conversion was found to decrease with the increase of WHSV. On the other hand, CO2 conversion increased with reaction temperature and pressure. Meanwhile, the methanol selectivity increased with WHSV and reaction pressure but decreased with the increase of reaction temperature. The apparent activation energy of methanol production at low reaction temperature (160 - 220 °C) was 10 kcal/mol. Non-Arrhenius behaviour of methanol formation was observed at high reaction temperature (220 - 260 °C). The performance of CZM/KIT-6 was maintained at high level, with the average methanol yield of 24.4 %, throughout the stability experiment (120-hour time-on-stream). In post-reaction XRD analysis, the copper crystallite growth was found to be 53.5 %, thus, resulting in 35.3 % loss of copper surface area.

In the present work, new Z-scheme N-BiOBr/NiFe2O4 nanocomposites were successfully constructed by a facile hydrothermal method. Various analytical characterization techniques were employed to examine the physicochemical and optical absorption properties of prepared photocatalysts. The prepared N-BiOBr/NiFe2O4 nanocomposites considerably enhanced the simultaneous visible light removal of phenol and Cr(VI) when compared with single-phase component photocatalysts. Especially, the N-BiOBr/NiFe2O4-15 nanocomposite demonstrated the top-flight photoactivity. The formed Z-scheme system in the nanocomposite significantly decreased the charge carrier recombination and improved the photoactivity. Photoluminescence and photoelectrochemical measurements were conducted to confirm the evidence of efficient charge carrier separation by the nanocomposites. Moreover, the N-BiOBr/NiFe2O4-15 nanocomposite can be magnetically separated and possessed good recycle performance up to five successive runs. The active species capturing experiments demonstrated that the hydroxyl radicals can degrade the phenol efficiently and that photogenerated electrons can reduce the Cr(VI). Finally, the mechanism of excellent photoactivity of N-BiOBr/NiFe2O4 nanocomposite was discussed.

The present study introduces a novel method for synthesis titanium hydride (TiH2) powder at low-temperature from ilmenite for powder metallurgy. The ilmenite converted to titanium tetrachloride (TiCl4) gas through the chlorination process. Next, TiCl4 reacted with magnesium hydride at different times and temperatures to produce TiH2 under a hydrogen atmosphere. The phase and morphology analysis of the obtained powders were studied using X-Ray Diffraction and Scanning Electron Microscopy techniques. The results indicated that the increase of reaction time and temperature enhanced the formation of TiH2 powder, which is a promising method for low-cost titanium hydride powder production.

Catalytic activity measurement were carried out on catalysts formulated from ZSM-5 zeolite separately loaded with transition metals (Cu, Co, Ni, Fe) for the removal of NOx in simulated diesel exhaust conditions. Various factors were investigated to compare the performance of these catalysts including catalyst preparation method, Si/Al ratio of the parent zeolite support, and durability in the exhaust stream containing water vapor or SO2. In many experimental conditions except in the presence of water vapor or SO2, Cu-ZSM5 remained the most active catalyst with 100% NOX conversion at around 350°C. C0-ZSM5 and Ni-ZSM5 could also achieve complete NOx conversion but at a much higher temperature of around 450°C. Fe-ZSM5 catalyst was the least active catalyst probably due to the formation of iron oxide particle, which accelerated formation of carbon monoxide.

Active absorbent for flue gas desulfurization was prepared from coal fly ash, calcium oxide (CaO) and calcium sulfate (CaSO4 ) by hydro-thermal process; steam and water hydration. The absorbents were examined and compared for its micro-structural properties. The experiments were conducted based on Design of Experiments (DOE) according to 24 factorial design. The effect of various absorbent preparation variables such as hydration period (Factor A), ratio of CaO to fly ash (Factor B), amount of calcium sulfate used (Factor C) and drying temperature (Factor D) towards the BET surface area of the absorbent were studied. The BET surface area of the absorbent was in the range of 12.9-169.3 m2/g. Fisher’s test showed that there is a strong influence of factor A, B and D towards the absorbent surface area, while its dependence on factor C is negligible. Comparison between absorbents prepared from water and steam hydration showed that the BET surface area of absorbents prepared from water hydration gives a higher surface area, but at a lower rate. The optimum BET surface area for the prepared absorbent 169.3 m 2 /g, was obtained at the following absorbent preparation variables using water hydration; hydration period of 24 hours, ratio of CaO to fly ash of 1:2, CaSO4 amount of 3 g and drying temperature of 200°C.

In this study, the catalytic performance of cobalt aluminate as an oxygen carrier catalyst was investigated in the dry reforming of methane (CH4). The series of cobalt aluminate with different cobalt (Co) content ranged between 18.32% and 45.85% were synthesized by the sol-gel method with aim of inducing the its ability as an oxygen carrier catalyst for dry reforming while suppressing the rate of carbon deposition. The reducibility of the developed catalysts corresponded with the initiation of CH4 oxidation at reaction temperatures between 700 °C and 900 °C. Successive oxidation-reduction of CH4 and carbon dioxide (CO2) invoked a novel reaction mechanism for the production of syngas through the reduction of the catalyst by CH4 and regeneration with CO2. A stability test was conducted on the best performing cobalt aluminate catalyst with 33.33% of Co content. The result showed the sustainability of the catalyst for up to 30 h of continuous reaction with an average yield of hydrogen (H2) and carbon monoxide (CO) at 97.2% and 99.7%, respectively. The amount of CH4 converted into deposited carbon was measured at approximately 1.9%. This current research on cobalt aluminate highlights the possibility of producing syngas through simultaneous oxidation-reduction of CH4 and CO2.

The synthesis of high quality graphene via economic way is highly desirable for practical applications. In this study, graphene flake was successfully synthesized on Cu/MgO catalyst derived from recovered Cu via etching in ammonium persulfate solution. Recovered Cu acted as efficient active metal in Cu/MgO catalyst with good crystal structure and composition according to XRD and XRF results. FESEM, EDX, HRTEM, Raman spectroscopy and SAED analysis were carried out on the synthesized graphene. The formation of single, bilayer and few layer of graphene from Cu/MgO catalyst derived from recovered Cu was feasible.

The performance of pure anatase titanium dioxide (TiO2) annealed at different temperatures as photoanode in the application of dye-sensitized solar cell (DSSC) was investigated and discussed. All samples of TiO2 were deposited on fluorine-doped tin oxide (SnO2) on glass substrate using spray pyrolysis deposition (SPD) method. Characterizations of the DSSCs fabricated were executed on their surface morphology, structural property, and energy conversion efficiency. In the DSSC preparation, anatase TiO2 thin films, platinum (Pt), ruthenium-based dye N719 and DPMII triiodide couple electrolyte were used as photoanodes, cathode/counter electrode, dye sensitizers and liquid electrolyte, respectively. All of the TiO2 photoanodes were annealed at 300 °C, 400 °C and 500 °C with a set left without any heat treatment. The thickness of anatase TiO2 photoanodes measured were in between 23 μm and 41 μm. The power conversion efficiency of DSSCs performed under visible light with intensity of 100 mW/cm2 shows that DSSC with pure anatase phased TiO2 annealed at 500 °C as photoanode yields the highest efficiency of 3.25%.

Photocatalytic technology utilized semiconductors and renewable solar energy have been envisaged as one of the most privileged solutions to assuage and even circumvent both the world catastrophe of energy crisis and environmental problems. Hitherto, a myriad of visible light-responsive photocatalysts have been explored for their photocatalytic applications. This article summarized the recent progress on the perovskite bismuth ferrite oxide (BiFeO 3 , denoted as BFO) as a new class of visible light-responsive photocatalyst for the photocatalytic treatment of organic pollutants. Description on the crystal and band structures of BFO, degradation pathways of BFO in visible light photocatalysis and unique features of BFO photocatalysts were presented. The techniques utilized to synthesize the BFO as well as the modification approaches partook in the photoactivity improvement were also detailed. Finally, summary and perspectives on the current challenges faced in expanding BFO advanced photocatalysts for the possible improvement in the environmental pollution remediation were discussed.

The quest for efficient and selective catalysts for conversion of glycerol monoglyceride is critical for the development of reliable methods for its synthesis. Thus, various types of catalyst and methods of catalyst manufacturing for conversion of glycerol to monoglycerides have been investigated. Acid-functionalized mesoporous catalysts are emerging as highly efficient catalysts for conversion of glycerol into monoglyceride. The incorporation of acid components into different mesoporous silicas for this application is reviewed in this work. The superiority of mesostructure catalysts in comparison to microporous catalysts has been elucidated in terms of accessibility to active sites, pore diffusion, thermal stability of the catalyst and catalyst reusability. Recent direction of novel acid-functionalized mesoporous catalysts development for this application is also critically reviewed.

Copper modified graphitic carbon nitride nanosheets (Cu-g-C 3 N 4 ) was synthesized and used in the hydroxylation of benzene under mild conditions with hydrogen peroxide as a “green” oxidant. The presence of copper ions (Cu 2+ ) was confirmed from the XPS, EDX and also the hydrogen TPR analyses. The catalyst shows excellent activity, resulting in 74.1% conversion of benzene with phenol as the major product (97.5%) and only p -benzoquinone as the by-product. The catalyst’s selectivity towards phenol did not exhibit significant change even after being reused for several cycles. The catalyst was also used for the oxidation of several other organic compounds with interesting results.

One of the promising methods to produce low cost titanium powder is to produce titanium hydride (TiH2) powder and transform it to Ti powder through dehydrogenation process. Another advantage of this method is the possibility to produce low oxygen content Ti for powder metallurgy. In this study, the reduction of titanium tetrachloride (TiCl4) to TiH2 was investigated with magnesium hydride (MgH2). The experiments were conducted under hydrogen atmosphere to promote the production of TiH2. The studied parameters included the reaction time and temperature. In order to minimize the energy consumption, the temperature range was set between 400 °C and 500 °C. Characterization study of the samples was performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The results indicated that TiCl3 was formed as an intermediate compound, and with increasing in reaction time up to 12 h, TiH2 amount started to increase.

In this work, the novel direct synthesis method of dimethylacetamide-based graphene oxide (GO) was performed through electrochemical exfoliation assisted by commercially available single-tail sodium dodecyl sulphate (SDS) surfactant. Then, the synthesised GO (SDS–GO) was incorporated into polyvinylidene fluoride (PVDF) solution to produce a nanofiltration (NF) membrane through the phase immersion method. The addition of GO into the preparation of membrane solution alters the membrane morphology and improves the hydrophilicity. TiO2 was also used as an additive for the NF membrane fabrication to further increase the membrane hydrophilicity. The fabricated PVDF/SDS–GO/TiO2 and PVDF/SDS–GO NF membranes were compared with pure PVDF membrane. Then, the fabricated NF membranes were tested for methylene blue (MB) rejection with 10 ppm MB concentration. On the basis of the dead-end cell measurement operated at the pressure of 2 bar, the PVDF/SDS–GO/TiO2 presents high MB rejection (92.76%) and the highest dye flux (7.770 L/m2 h). This dye flux value was sevenfold higher than that of pure PVDF membrane (1.146 L/m2 h) which was due to the utilisation of both GO and TiO2 that improved the membrane hydrophilicity as indicated by the lowest contact angle (64.0 ± 0.11°). High porosity (57.46%) also resulted in the highest water permeability (4.187 L/m2 h bar) of the PVDF/SDS–GO/TiO2 NF membrane.

The effect of synthesis method on the ultimate properties of copper-based catalysts supported on KIT-6 was investigated. A series of catalysts with 0.60Cu/0.15ZnO/0.05MnO/1.0KIT-6 mole ratio was synthesized using three methods, i.e. citric acid impregnation (CA), wet impregnation (WI), and deposition-precipitation (DP). Characterization study shows the catalyst synthesized using CA method had relatively high metal-support interactions and preserved the structures of preshaped KIT-6 support the best. The CA catalyst was also characterized with low mesopore plugging, high porosity, along with the formation of small copper crystallites and large copper surface areas. The presence of abundant accessible active sites in CA catalyst is strongly supported by temperature-programmed desorption results. After reaction, X-ray diffraction analysis indicates CA catalyst had greatest resistance to copper crystallite growth. In direct CO2 hydrogenation reaction, the CA catalyst led to remarkably high methanol production rate (3.94 kg/kgcat·h), i.e. 34%–164% higher than the others, including a commercial catalyst.