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Fiber-based activated carbons were prepared from phenolic and rayon fibers through physical activation methods. The raw materials were activated using steam and CO2, and the resultant activated carbons were characterized for pore distribution, textural properties and heavy metals removal. Two commercial activated carbon fibers, namely Fe400 and A10 were also employed for comparison. Activated carbon fiber with a higher specific surface area of 2938 m2/g was prepared from phenolic fiber by steam activation at 900 °C for 1 h. The material is microporous with pores concentrated at supermicropore region. The activated carbon fiber also demonstrates a greater removal of copper(II) and lead(II) at 50% and 75%, respectively, tied-up with its textural properties.

The present work was aimed to evaluate the performance of low-cost activated carbon from coffee residue for Bisphenol A removal. Coffee residue was activated using phosphoric acid and iron (III) chloride. The resultant activated carbons were characterized for textural properties, surface chemistry and surface morphology. The results show that AC-CoR I (H3PO4-activated coffee residue carbon) exhibits high surface area of 1030 m2/g and mesopore size of 2.13 nm, favourable for Bisphenol A removal at 105 mg/g. The adsorption data fitted well with the pseudo-second-order and Langmuir models. In conclusion, coffee residue is a promising precursor of activated carbon for wastewater treatment.

The fundamental understanding about dielectric properties is not completely understood even though it is crucial in microwave-assisted heating. The present work was aimed at evaluating the dielectric properties of reagent mixtures and solids of potassium hydroxide-treated castor residue carbons at varying frequencies and temperatures. Chemical treatment at solid mass ratios (KOH pellet:castor residue) of 0.0 to 2.0 in 50 mL water was carried out using a microwave oven at 70% intensity. The dielectric properties were determined using an open-ended co-axial probe. Results show that the dielectric properties of materials changed with frequency, temperature, water content and ionic strength. Also, the presence of potassium hydroxide solution aids in improving the propensity of castor residue to be heated via microwave. The potassium hydroxide-treated carbons exhibit a 90% removal efficiency of methylene blue at Co = 189 mg/L.

This work was aimed at evaluating the adsorptive properties of beta-cyclodextrin (β-CD) adsorbent towards methylene blue and congo red dyes removal. The adsorbent was characterized for specific surface area and surface chemistry. The results show that the surface area of β-CD adsorbent is small at 0.1 m2/g and the surface chemistry is rich in acidic oxygen groups. The dyes adsorption onto β-CD is favourable. Congo red adsorption exhibits a greater rate constant of 0.103 min−1 and a relatively shorter time to reach equilibrium at 40 min as opposed to 1500 min for methylene blue. On a molar basis, both dyes display a comparable maximum capacity of 1.80 × 10−2 mmol/g, with β-CD shows a greater affinity for congo red. The congo red adsorption is governed by hydrophobic host-guest complex interactions, while that for methylene blue is thru weak electrostatic interactions at the hydrophilic exterior of β-CD. To conclude, β-CD could be a promising adsorbent candidate for the treatment of dyes wastewater, where future works will be centred in improving the versatility and performance of the material.

This work is the part of a study on the enhancement of thermo-mechanical properties of Epoxy by incorporating carbon and glass fiber and preparing epoxy composites and are rarely used before. The composite/laminates of Carbon fiber/Epoxy (CFE) and Glass fiber/Epoxy (GFE) having 1.5 mm thickness were prepared by hand layup vacuum bagging technique. The fiber-epoxy ratios for preparation of CFE and GFE were 40:60, 50:50 and 60:40 by weight percent. Thermal properties of the composites were investigated using Differential Scanning Calorimetry (DSC), while mechanical properties were examined using Universal testing machine (UTM) in terms of tensile strength and Young’s modulus. The tensile strength of CFE were enhanced to 844.44%, 951.11% and 1122.22% by incorporation of carbon fiber having 40, 50 and 60 wt%, respectively. While the increase of 156.66%, 171.10% and 197.77% in tensile strength of GFE was noticed when 40, 50 and 60 wt% of glass fiber was incorporated. The glass transition temperature (Tg) increased from 71 °C of neat epoxy to 110 °C for both the epoxy composites. Overall, the properties of CFE were found to be much superior to that of GFE.

This study was aimed at evaluating the physicochemical properties and oxidation stability of castor oil using microwave-assisted solvent extraction (MAE). MAE was performed using 5% ethanol in hexane as solvent at different extraction times, power intensities and solvent-to-feed (S/F, ml of solvent to gram of feed) ratios. The process parameters were optimized by statistical approach using historical data design of response surface method (RSM). The oils were characterized for yield, physicochemical properties, dielectric properties and oxidation stability, and comparison was also made with oil extracted using Soxhlet method. Results show that the maximum oil yield of 37% was obtained at 20 min with microwave power intensity of 330 W and S/F ratio of 20. The main fatty acid composition of castor oil is ricinoleic acid. The density, refractive index, dielectric properties and oxidation stability of oils are not affected by the extraction methods and extraction parameters of MAE. However, the MAE-extracted oil is more viscous compared to that by Soxhlet method. With extra caution on oil oxidation, MAE could be a promising solvent extraction method with an 86% less in processing time and a higher yield.

A severe problem associated with combustion of fossil fuels and biomass in the quest for heat and power generation is the release of acidic gases. This posed great health and environmental concerns, and their presence in sufficient amount in flue gas affects the performance of CO2 capture system through formation of heat resistant salts on reaction with the capture medium. Among the various alternatives, removal of the SO2 and NOx gases by adsorption on surface modified activated carbon from renewable sources has proven to be an efficient and robust technology which is attributed to the presence of immobilized chemical species on the carbon surface providing the necessary affinity with the target gaseous pollutants. Thus, the present review aimed at providing a cutting-edge critical assessment of research outputs on SO2 and NOx adsorption from flue gas by surface modified activated carbon. Conspicuously, modification mechanisms, surface characterization, surface chemistry and application of surface modification of activated carbon were discussed elaborately.

This work was aimed to evaluate the adsorptive properties of sodium hydroxide-activated Casuarina empty fruit carbons for methylene blue and congo red removal. The activated carbons were prepared at varying NaOH ratios and characterized for specific surface, functional groups, thermal stability, and the pH at the point of zero charge. Batch adsorption was performed at varying concentrations, contact times, and temperatures. The specific surface of activated carbons decreased with increasing ratio, but the maximum capacity increased. The methylene blue capacity onto AC2.5 is 530 mg/g, while for congo red onto AC2.0 is 232 mg/g. The equilibrium data fitted well with the Langmuir model, while the kinetics could be described by the pseudo-second-order model. The thermodynamics indicate that the adsorption is endothermic and spontaneous at high solution temperature.

The present work was aimed to evaluate the adsorption properties of Casuarina fruit-based activated carbons to remove cationic (methylene blue) and anionic (congo red) dyes. The roles of activators on the characteristics and performance of activated carbons were studied. Activated carbons were characterized for textural characteristic, surface morphology, surface functional groups, elemental composition, thermal degradation analysis and pH at the zero point of charge (pHpzc). The specific surface of the materials is between 2.33 m2/g and 1511 m2/g. Batch adsorption was conducted at varying concentrations, contact times and temperatures. Results show that KOH activation yields activated carbon with excellent maximum capacities of 615 mg/g and 339 mg/g for methylene blue and congo red, respectively. The adsorption data displayed a good regression with Langmuir and pseudo-second-order kinetic models. Both intraparticle and film controlled the diffusion of dye molecules onto the carbon surface. The adsorption is endothermic and spontaneous at high temperature especially for methylene blue removal.

A highly microporous activated carbon from yarn sludge (YSAC) was developed via composite activation using KI and KOH. The activated carbons were characterized for elemental composition, textural properties, morphology, and surface chemistry. YSAC exhibits a high specific surface of 1037 m2/g, which yields a malachite green (MG) capacity of 498 mg/g. YSAC is primarily negatively charged with the highest total acidic groups of 1.56 mmol/g. MG adsorption by YSAC could be described as monolayer coverage onto homogeneous structure, where the transport is controlled by film diffusion. From the thermodynamics viewpoint, the adsorption is endothermic and spontaneous.

The aim of the present work is to determine the solubility of castor oil by using supercritical carbon dioxide as extracting solvent. A simple dynamic technique was used to obtain the solubility of castor oil in supercritical carbon dioxide. The solubility was measured at temperatures ranging from 313 to 335 K and pressures from 20 to 36 MPa. Under extraction conditions, the measured solubilities were in the range from 1.29 × 10 −3 to 4.88 × 10 −3 (g of oil)/(g of CO 2 ). Measurements confirmed that temperature and pressure have direct effects on solubility-enhancement factors. Five semi-empirical models were tested for their ability to correlate experimental data: the Chrastil, Del Valle Aguilera (VA), Bartle, Kumar and Johnston (KJ), and Mendez-Santiago and Teja (MST) models. Over the temperature and pressure ranges studied, solubilities from these models had the following average absolute relative deviations from experimental data: Chrastil, VA, Bartle, KJ and MST models with an average absolute relative deviation percent (AARD%) of 0.05%, 0.30%, 0.38%, 5.98% and 28.4%, respectively. Thus, the Chrastil, VA and Bartle models correlated the castor oil solubility data with the lowest AARD%.

Activated carbon pellet (ACP) is advantageous to the industrial-based adsorption process owing to its easy handling, large volumetric adsorption capacity and good mechanical properties. This study introduces a straightforward phosphoric acid-impregnated sawdust as economical binder to convert textile sludge activated carbon powder into water resistant pellets. The effects of activation time and drying technique on the physicochemical and mechanical properties of ACPs were investigated. The materials were characterized using N2 gas adsorption-desorption, scanning electron microscope, Boehm titration, pHpzc and compressive strength test. It was discovered that the physiochemical properties of ACPs were close to that of base activated carbon. Moreover, a longer activation time promotes the development of micropore on ACPs and enhances the compressive strength. The microporosity, surface area and compressive strength of ACPs are in the range of 16–23%, 668–979 m2/g and 0.4–1.5 MPa, respectively. The ACP prepared at 560 °C for 3 h showed a 395 mg/g of malachite green removal, whilst retaining its cylindrical shape. The Langmuir model gave the best conformity to the equilibrium data, suggesting a possible monolayer adsorption onto ACPs. This study demonstrated the potential of sawdust as low-cost binder and the applicability of ACPs in dye adsorption.

Environmental pollutions from pigment-containing wastewaters from various industrial sources are of concern nowadays. Conventional treatment techniques are efficient but sometimes create secondary pollution that requires further disposal. Utilization of agricultural waste biomass such as from the pineapple (Ananas comosus) industry offers an interesting alternative based on its potential to be converted into activated carbon. In this study, activated carbon was prepared from the pyrolysis (500 °C, 1 h) of pineapple waste biomass (leaves, stem, crown) impregnated with ZnCl2. Resulting activated carbon with the highest surface area was chosen for subsequent studies and was characterized for its surface area, surface chemistry properties, functional groups, porosity and surface morphology. The activated carbon was evaluated for its dye removal efficiency using methylene blue (MB) taking into consideration the following parameters; contact time, initial concentration of MB and adsorbent dosage. Maximum uptake (qmax) of MB by the adsorbent was determined based on goodness-of-fit according to the Langmuir, Freundlich and Redlich Peterson adsorption isotherm models. The adsorption equilibrium data was best fitted with the Langmuir adsorption isotherm with R2 of 0.969 and qmax at 288.34 mg/g. It can be concluded that adsorbent prepared using a 1:1 ratio has the highest dye removal capacity due to its high surface area (914.67 m2/g) and adsorption capacity at 288.34 mg/g. Thus, this study demonstrated the potential of using pineapple waste biomass as cheap and efficient raw materials to produce activated carbon for dye removal from wastewaters.

Volatile organic compounds (VOCs) have been reported to be responsible for many acute and chronic health effects and environmental degradations. In this study, coconut shell based porous carbon was produced through chemical activation with potassium hydroxide (PHAC) and chemically treated with ammonia (PHAC-AM) to improve the adsorption of benzene and toluene. The porous carbons were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nitrogen adsorption tests. Removal efficiencies and adsorption capacities of the activated carbon samples for benzene and toluene were carried out through batch studies. Langmuir, Freundlich and Temkin adsorption isotherms were tested for the adsorption process and the experimental data were best fitted by Langmuir model. Pseudo-second-order kinetic model best described the adsorption kinetics for the two VOCs on PHAC and PHAC-AM. The removal of benzene and toluene by PHAC are; 82.5 and 85.6%, while that of PHAC-AM are; 91 and 92.3% respectively with approximately 10% increase in the uptake after the ammonia treatment. After five cycles of adsorbents regeneration test, approximately 50% of benzene and toluene was still able to be removed. The results of this study revealed that ammonia treated activate carbon (PHAC-AM) is a sustainable adsorbent for treatment of VOCs in polluted waters.

The optimal conditions of oil yield from castor (Ricinus communis L) seed using supercritical CO2 as extracting solvent were studied. Response surface methodology (RSM) was employed to show explicitly the influence of the process parameters such as temperature, pressure and the CO2 flow rate on the oil yield using Box–Behnken design. The linear terms of pressure, CO2 flow rate and temperature and the quadratic terms of temperature, pressure and CO2 flow rate, had a significant effect on the oil yield. The maximum oil yield obtained from the mathematical model was predicted to be 9.29% under the conditions of temperature 63.72 °C and pressure 29.90 MPa with CO2 flow rate of 4.15 mL/min. The fatty acid constituents of the seed oil extracted using supercritical CO2 were determined by gas chromatography–mass spectrometry (GC–MS) and Fourier transform infrared spectrometer (FTIR). Palmitic, stearic, oleic, linoleic, linolenic and ricinoleic acids were identified by GC–MS analysis after the formation of fatty acid methyl ester (FAME).

Two operating solvent extraction conditions, i.e. average particle size and extraction time, were optimized by a response surface method using Box–Behnken design to obtain high oil yields. The extraction was conducted by the soxhlet method using ethanol, n-hexane and petroleum ether as solvents. Statistical analyses and analysis of variance indicated that the operating conditions are significant factors affecting the yield. For the modeled extraction, yields of 59.8%, 52.3% and 49.9% were determined for optimized average particle sizes and extraction times of 1.30 mm and 2.88 h, 1.26 mm and 2.65 h and 1.25 mm and 2.55 h, respectively. The physicochemical properties of castor bean oils were evaluated. The extracted oils contain refractive indices of 1.4771, 1.4770 and 1.4772, unsaponifiable contents of 0.6, 0.45 and 0.5%, volatile contents of 0.48, 0.55 and 0.28%, free fatty contents of 0.8, 0.3 and 0.27%, phospholipid values of 0.03, 0.05 and 0.03%, peroxide values of 12.4, 3.3 and 3.5 meq O2/kg, iodine values of 85.6, 84.5 and 85.0 g/I2/100 g of oil, saponification values of 174.6, 176.3 and 173.8 mg of KOH/g of oil, acid values of 1.60, 0.60 and 0.53 mg KOH/g, respectively. The analyses indicate that the oil is suitable for use in the oleo-chemicals industry.

This work was aimed to characterize ash-rich adsorbent derived from palm oil mill effluent sludge (POME sludge) for heavy metals removal from aqueous solution. The adsorbents were characterized according to specific surface area, surface morphology and elemental compositions. Sludge adsorbent exhibits high adsorption capacity for both copper(II) and lead(II), while its ash derivative demonstrates comparable removal of lead(II). Results indicate the important role of sludge ash in the adsorption of heavy metals. The study suggests the potential use of ash-rich POME sludge for industrial wastewater treatment.

Thermodynamic properties of ethanol-glycerol dry reforming have been studied with the method of Gibbs free energy minimization for hydrogen production from ethanol-glycerol mixture. Equilibrium compositions were determined as a function of CO 2 /ethanol-glycerol molar ratios (CEG)(1:1-12:1) where ethanol-glycerol is 1:1; reforming temperatures (573-1273 K) at different pressures (1-50 bar). Optimum conditions for hydrogen production are temperatures between 1073 and 1273 K and CEG of 1:1 at 1 bar pressure, whereas temperatures above 1073 K and CEG ratio 1:1 and 1 bar are suitable for the production of synthesis gas. Higher pressure and higher CEG ratio does not encourage hydrogen formation. Under identified optimum conditions, carbon formation can be thermodynamically inhibited

The use of microwaves to assist the preparation of activated carbon has been widely published in literature. However, there are critical issues regarding the microwave principles that have been ignored. This article is aimed to provide remarks on the recent progress, and to address critical aspects that are of interest, yet have been neglected in much of published study. Issues highlighted here are worth to be considered to ensure the reliability and reproducibility of the microwave-assisted process, especially in large scale production.

Activated carbons were prepared from cattle manure compost (CMC) using zinc chloride activation. The structural and surface chemical characteristics of CMC-based activated carbons were determined by N 2 adsorption–desorption and Boehm titration, respectively. The water vapor adsorption properties of the prepared activated carbons with various pore structure and surface nature were examined, and the mechanism of water adsorbed onto activated carbon was also discussed. The results show that the adsorption of water vapor on carbons begins at specific active sites at low relative humidity (RH), followed by micropore filling at medium RH through the formation of pentamer cluster of water molecules in the narrow micropores. The water vapor adsorption capacity of activated carbon is predominantly dependent on its pore volume and surface area. Although capillary condensation is not the mechanism for water adsorption onto activated carbon, water can adsorb on narrow mesopore to some extent.

A batch adsorption system was employed to develop the adsorption properties for Cu (II) and Pb (II) by using cattle manure compost (CMC) derived carbons activated by ZnCl2. Langmuir and Freundlich models were applied to describe the adsorption data. The uptake performance of heavy metal ions onto the cattle manure compost activated carbon was evaluated and compared with the commercially available activated carbon, F400. The Langmuir plots were well fitted to linear approximation, and the derived carbons showed favorable adsorption more towards copper (II) than lead (II). Adsorption capacity of copper by out-gassed CMC activated carbons was better than that of out-gassed F400, though it was comparable prior to the de-ashing and out-gassing treatments. Results proposed that nitrogen content of cattle manure compost was responsible for the preferable removal of copper over lead.