Search

The current environmental pollution and global warming may cause a serious ecological crisis. The conversion of renewable resources, especially from biomass could be a promising option to alleviate this crisis. Traditionally, carbon produced from petrochemicals and coal are typically using large amount of energy and produce substantial quantities of pollutants. There is a need to develop alternative and effective methods to synthesize carbon from renewable resources with high performance and minimal environmental impact. Biochar is a rich carbon material derived from plant-based biomass. Biochar is one of the most ideal materials in various applications by considering it is low thermal conductivity, high porosity, high surface area, renewability, high stability, high carbon content and bulk density. In this regard, biochar has been widely recognized as the suitable candidate for sustainable carbon material. Thus, in this review, recent progresses towards the applications of biochar-based materials in various applications, such as wastewater treatment, soil amendments, catalyst or catalyst precursors and energy storage, are summarized and discussed. The various sources of biomass, synthesis techniques, and the effects of various factors involved in the carbonization process to generate different physicochemical properties biochar from the biomass is elaborated. Also, this review is highlighting the characteristics of the biochar and the carbonization mechanisms of different synthesis technologies. This review shows the great potential of different applications of biochar, which is expected to simulate new development to promote the use of biochar materials to achieve a sustainable environment and circular bio-economy. [Display omitted] • Discussed the biomass feedstock for biochar materials. • The relationship between factors, production technologies and the physicochemical properties of biochar. • The synthesis and preparation methods of biochar materials affect their applications. • The challenges covered to develop economically feasible biochar production technologies. [ABSTRACT FROM AUTHOR]

• Highly active Na 2 O impregnated-CNTs nanocatalyst was prepared and synthesized. • Positive metal cations possess Lewis acidity that increases the catalytic activity. • Na 2 O impregnated-CNTs nanocatalyst gave above 97% of FAME yield. • Leaching of Na+ lower than 5 mg L−1 as required by EN14214 international standard. The present work demonstrated the preparation of sodium oxide impregnated on carbon nanotubes (CNTs) and its application as a heterogeneous catalyst for transesterification of waste cooking oil. The catalyst was prepared by impregnation of metal oxide such as sodium oxide, Na 2 O on the CNTs by calcination at 500 °C for 3 h. It was assumed that the positive metal ion which is Na+ (cations) possess Lewis acidity, whereby, high negativity of oxygen ions can acts as the Brønsted bases, which could enhance the activity of the catalyst. The characterization of synthesized Na 2 O impregnated-CNTs nanocatalyst was performed using Temperature-programmed desorption of carbon dioxide (TPD-CO 2), X-ray diffraction (XRD), infrared spectroscopy and Field emission scanning electron microscope (FESEM). Herein, the mechanism of the transesterification process assisted by the Lewis acidic metal oxide on carbon support was proposed and explained. Series of reactions were carried out to determine the performance of the catalyst. It was found that the prepared Na 2 O (20 wt%) /CNTs catalysts yielded above 97% of FAME yield at 65 °C assisted by 3 wt% of catalyst amount and 20:1 of methanol-to-oil molar ratio in 3 h of reaction time. Moreover, the results on catalyst's reusability indicated that the catalyst could last for 3 subsequent reaction cycles due to deactivation of the catalyst caused by leaching of metal oxides and poisioning effect on the active sites. It can be concluded that the prepared Lewis acidic carbon catalyst has a potential to catalyse the production of biodiesel from waste cooking oil (WCO). [ABSTRACT FROM AUTHOR]

Biodiesel is one of the ideal options, considering it is a renewable, biodegradable, non-toxic, environmentally friendly fuel with low pollutant emission. However, biodiesel encounters challenges, mostly connected to its high manufacturing costs, that hinder its continued development and advancement. Focusing on more affordable and environmentally friendly inputs, such as suitable and abundant feedstock and efficient catalysts, is crucial. This paper aims to summarize the literature on biodiesel production and life cycle assessment (LCA) studies, critically review the catalyst and oil feedstock employed, and the findings of the LCAs, focusing on spotting prospective low-cost feedstock sources. Furthermore, an overview of recent LCA-related works applied in various biodiesel processes incorporating various catalysts and oil feedstock was evaluated. The application of LCA and its environmental impacts in biodiesel production was discussed and summarised in table form. The importance of using a sustainable and favorable approach could result in cost-efficient biodiesel production. Additionally, the advantages and limitations of the LCA in biodiesel production have been discussed. Last, the status and challenges of LCA in biodiesel production are covered. The findings of using cheaper feedstock are expected to inspire future studies and help industry professionals develop sustainable biodiesel production. • A comprehensive review of LCA framework and biodiesel process technologies were covered. • LCA of biodiesel production using various catalysts and oil feedstock was reviewed. • Challenges and status were discussed for sustainable biodiesel production. [ABSTRACT FROM AUTHOR]

A highly mesoporous activated carbon derived from palm kernel shell was successfully prepared by hydrothermal-assisted carbonization (HTC) by improving the degradation of lignocellulosic composition and increase the porous texture of carbon structure. Additional NaOH treatment increased the surface area of the catalyst which enhanced the loading of the active site. Further impregnation of HTC based activated carbon with K 2 CO 3 and CuO via wet impregnation provided bifunctional characteristics suitable for simultaneous esterification and transesterification processes. The physicochemical properties of the prepared catalysts were conducted through the state-of-the-art techniques including N 2 adsorption-desorption analysis, functional group determination, surface morphology study, electron dispersive x-ray mapping, elemental distribution analysis, amount of basicity and acidity strength and thermal degradation behavior analysis. The investigation found that the chemical treatment with NaOH significantly increased the surface area from 3.57 to 3368.60 m2/g and impregnation with K 2 CO 3 and CuO offered higher amount of basicity of 5.73 mmol/g and acidity of 1.48 mmol/g, respectively. These properties enhanced the simultaneous esterification-transesterification of waste cooking oil to biodiesel. The catalytic study produced 95.36 ± 1.4% of biodiesel over 4 wt% of PKSHAC-K 2 CO 3(20%) CuO (5%) catalyst, 12:1 of methanol to oil molar ratio, reaction temperature of 70 °C for duration of 2 h. Meanwhile, the catalyst can be employed for five subsequent reaction cycles with FAME yield of 82.5 ± 2.5%. Thus, the synthesized bifunctional nanocatalyst supported on the HTC based activated carbon has been validated as an efficient catalyst for biodiesel production. Image 1 • Hydrothermal-assisted carbonization creates high surface area of 3368 m2/g. • Large surface area provides high surface for metal impregnation. • Amount of basicity and acidity was improved with high loading of active sites. • Reaction over PKSHAC-K 2 CO 3(20%) CuO (5%) produced 95.36 ± 1.4% biodiesel from WCO. • Catalyst can be reutilized for 5 cycles with <80% biodiesel. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) photocatalysts are suitable for wastewater treatment via photocatalytic processes. However, they are hindered by fast e− and h+ recombination, a large bandgap, and the need for a high-energy light source for activation. Thus, this study was aimed to synthesize a photocatalyst that operates under a low-energy consumption. We introduced cadmium sulphide (CdS) heterojunction to ZnO photocatalyst, and successfully reducing their bandgap from 3.30 eV to 2.46 eV. This modification allows activation with a 21-Watt light-emitting diode (LED) visible light source. The surface structure characteristics of the ZnO/CdS photocatalyst was analyzed using XRD, HRTEM, FESEM, and N 2 adsorption-desorption isotherms. UV-NIR was used for bandgap analysis and the DFT simulation method to compute the atomic properties of the materials. Catalytic evaluation showed that the ZnO/CdS photocatalyst completely degraded the model dye solution (100%) using 0.5 g of Z 3 C 1 (3:1 M ratio) of 100 mg L−1 MB solution at pH 9 within only 90 min. A scavenger test confirmed that the hydroxyl OH• and superoxide •O 2 − radicals proved were the major active species responsible for degradation process. The reusability of Z 3 C 1 was demonstrated over 4 reaction cycles, proving that CdS significantly enhances visible light absorption by extending the photo-response range and promoting superior formation of e− and h+. This delays their recombination due to the Z-scheme type, making it highly potential for wastewater treatment. [Display omitted] • Excellent Z-scheme ZnO/CdS heterojunction photocatalyst was prepared successfully. • CdS enhances visible light absorption by reducing the bandgap from 3.30 eV.→ 2.46 eV. • The electronic DFT band structure of Z-scheme ZnO/CdS was successfully calculated. • OH.• and •O 2 − radicals serve as major active species responsible for photodegradation. • The ZnO/CdS photocatalyst successful degrades 100% dyes molecules within 90 min. [ABSTRACT FROM AUTHOR]

The use of carbon-based catalysts has drawn so much interest in biodiesel production due to improved reaction performance. However, there was lack of comprehensive studies in term of its kinetic and thermodynamic perspective. Therefore, a methodical study is essential to uncover the influence of the carbon catalyst with respect to reaction rate and yield. This study represents kinetic and thermodynamic of heterogeneously K 3 PO 4 /AC-catalysed transesterification. It was done correspondingly via pseudo-first order mechanism and Eyring-Polanyi equation, whereby, under the optimal reaction temperature of 333.15 K, all data have fitted satisfactorily in both models with resulted R 2 of 0.99, respectively. Activation energy (E a ) and Gibbs free energy (ΔG) were calculated as 34.2 kJ mol −1 and −33.68 kJ mol −1 , indicating the reaction was exergonic and spontaneous at high temperature. [ABSTRACT FROM AUTHOR]

Fatty acid methyl esters (FAME) production from waste cooking oil was successfully carried out using a newly developed heterogeneous biomass-based catalyst. Activated carbon produced from oil palm biomass was calcined with potassium phosphate tri-basics (K 3 PO 4 ) in order to synthesize a high catalytic heterogeneous catalyst. As it is characterized with substantial surface area of 680 m 2 /g and basicity amount of 11.21 mmol/g, 98% of FAME yield was achieved under optimum reaction parameters of 5 wt% catalyst loading, 12:1 methanol to oil molar ratio at 60 °C for 4 h. The catalyst was shown to be reusable, with more than 76% FAME yield after 5 consecutive cycles. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) provides alternatives technique to produce a nanosize activated carbon from biomass with a high surface area. Herein, this study we prepared empty fruit bunch-based activated carbon (EFBHAC) using HTC technique. The activated carbon was then functionalized with K 2 CO 3 and Cu(NO 3) 2 to produce bifunctional nano-catalyst for simultaneous esterification-transesterification of waste cooking oil (WCO). The physicochemical properties were performed i.e. N 2 sorptions analysis, TPD-CO 2 /NH 3 , FESEM, EDX, FTIR and XRD analysis. The results revealed that produced EFBHAC possessed a BET surface area of 4056.17 m2 g−1, with pore volume of 0.827 cm3 g−1 and 5.42 nm of pore diameter resulting from hydrolysis, dehydration decarboxylation, aromatization and re-condensation during HTC process. Impregnation of EFBHAC with K 2 CO 3 and Cu(NO 3) 2 granted a high amount of basicity and acidity of 9.21 mmol g−1 and 31.41 mmol g−1, respectively, accountable to high biodiesel yield of 97.1%, produced at the optimum condition of 5 wt% of catalyst loading, 12:1 of methanol to oil molar ratio at 70 °C for 2 h. More than 80% of biodiesel was produced after the 5th cycle depicted the good reusability. The transformations from WCO to biodiesel was confirmed via 1H NMR, FTIR and TGA analysis. Fuel properties revealed kinematic viscosity of 3.3 mm2 s−1, cetane number of 51, flash point of 160.5 °C, cloud and pour point of 11 °C and −3 °C, respectively. These results show the excellent potential of waste materials to prepare bifunctional nano-catalysts to produce higher biodiesel yield which has potential to be commercialized. [Display omitted] • Empty fruit bunch was transformed into high quality activated carbon via HTC process. • Catalyst support help to reduce costs as the reaction occurs on the catalyst surface. • Bifunctional nano-catalyst overcome saponification problem through one-pot reaction. • Produced biodiesel is proven to have quality equivalent to international standards. [ABSTRACT FROM AUTHOR]

A large amount of waste printed circuit boards (WPCBs) has been generated due to the tenacious scientific development and therefore, the improvement of expectations for everyday comforts. The unprecedented acceleration of electronic waste (e-waste) and informal disposal at end-of-life display the adverse impact of digitalization. Recently, home teleworking has increased a wide range of sectors and occupations which may eventually lead to increase the generation of e-waste. Effective management of e-waste is urgently required for protecting environment as well as human well-being's. In view of the precious metal content and rare earth elements, WPCBs could become a sustainable source of precious metals. Appropriate eco-friendly strategies to recover metals from WPCBs are therefore imperative and crucial for e-waste management. Recent progress in metal recovery through gravity, density, electrostatic and integrated approaches were investigated dependent on previous contribution to provide an overview of present recycling status. The mechanism and factors influencing the metal recovery efficiency in a countercurrent operation were critically reviewed. The application of biotechnological approach for metal recovery was discussed from the theoretical and experimental views. The hazardous impact on human health and environment due to the toxic substances released from e-waste were highlighted. Finally, the limitations and perspectives towards the sustainable process for recovery of metals from e-waste were discussed. [Display omitted] • Emerging trend of metal recovery from WPCBs was measured. • Integrated e-waste recycling process with environmental impact was considered. • Novel biotechnological approaches with genome reprograming strategy were emphasized. [ABSTRACT FROM AUTHOR]

The contamination of groundwater by arsenic (As) in Bangladesh is the biggest impairing of a population, with a large number of peoples affected. Specifically, groundwater of Gangetic Delta is alarmingly contaminated with arsenic. Similar, perilous circumstances exist in many other countries and consequently, there is a dire need to develop cost-effective decentralized filtration unit utilizing low-cost adsorbents for eliminating arsenic from water. Morphological synthesis of carbon with unique spherical, nanorod, and massive nanostructures were achieved by solvothermal method. Owing to their intrinsic adsorption properties and different nanostructures, these nanostructures were employed as adsorption of arsenic in aqueous solution, with the purpose to better understanding the morphological effect in adsorption. It clearly demonstrated that carbon with nanorods morphology exhibited an excellent adsorption activity of arsenite (about 82%) at pH 3, remarkably superior to the two with solid sphere and massive microstructures, because of its larger specific surface area, enhanced acid strength and improved adsorption capacity. Furthermore, we discovered that iron hydroxide radicals and energy-induced contact point formation in nanorods are the responsible for the high adsorption of As in aqueous solution. Thus, our work provides insides into the microstructure-dependent capability of different carbon for As adsorption applications. [Display omitted] • Novel micro-structured carbon-based adsorbents were used to removal arsenic (As). • The adsorbents were able to remove As more effectively than spherical and massive structured carbon. • Surface radicals and energy-induced contact point were enhanced the electrostatic interaction with As. [ABSTRACT FROM AUTHOR]