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Biochar is a byproduct of biomass pyrolysis that has been identified as an effective and novel bio-adsorbent for contaminant removal from wastewater. A pyrolysis-chemical activation process was used to convert eucalyptus tree bark to activated biochar, which was then characterized using various techniques (BET, SEM, FTIR, EDX, XRD and pHpzc) and used as a bio-adsorbent to remove hexavalent chromium (Cr(VI)) from aqueous solution. The effects of adsorption process conditions (adsorbate concentration, contact time, adsorbent amount and pH) on Cr(VI) removal efficiency were investigated. The best experimental conditions for the maximum equilibrium uptake of Cr(VI) by activated eucalyptus bark biochar (AEBB) were 10 mg/L, 140 min, 6.0 and 0.3 g/L for initial Cr(VI) concentration, contact time, pH and adsorbent amount, respectively. The AEBB's outstanding performance was aided by its high surface area, well-developed porous structure and dominance of active surface functional groups, as validated by BET, SEM and FTIR. The Freundlich model fitted the equilibrium data the best. The pseudo-second-order model appeared to better predict the kinetics of Cr(VI) adsorption onto AEBB, indicating the dominance of chemisorption.

The twin crises of fossil fuel reserves depletion and environmental degradation have motivated industrial and research community to seek alternative and renewable energy sources. Biodiesel has dominated the global scene due to numerous advantages associated with it. In this study, biodiesel was synthesized by transesterifying used cooking oil with three different alcohols: methanol, ethanol and mixed methanol-ethanol. The biodiesel samples produced using methanol, ethanol and mixed methanol-ethanol were denoted as BM, BE and BME, respectively. The properties of the biodiesel samples produced were evaluated in accordance with ASTM standards, and a B20 blend of the three kinds of biodiesel (BM20, BE20 and BME20) was tested in a compression ignition engine to evaluate its performance and emission characteristics. Results from the GC–MS analysis showed that alkyl (methyl or ethyl) ester content in BM, BE and BME samples were 97.72%, 91.83% and 84.65%, respectively, indicating that methanol-based biodiesel satisfied the minimum requirement of EN 14214 standard. In addition, a total of 27.6% methyl and 57.05% ethyl esters were contained in the BME sample, suggesting high ethyl ester conversion during methanolysis-ethanolysis reaction. CO emission values of BM20 blend were lower than those of B0, BE20 and BME20, while the B0 discharged the least NOX amongst the fuels tested. In addition, BM20 discharged the least HC compared to B0 and two other biodiesel blends. Based on this finding, it could be concluded that BM20 exhibited the best performance, combustion and emission characteristics amongst the fuels tested in diesel engine.

Recent researches have linked the use of synthetic coagulant for treatment of water with some neurodegenerative and neurotoxic diseases. In view of this, this study focused on the use of an eco-friendly natural coagulant, Moringa oleifera seed for the treatment of surface water. In order to obtain lowest turbidity of surface water, optimization of process variable affecting the coagulation of water was carried out using Response Surface Methodology (RSM). Four parameters were varied viz. settling time, agitation time, agitation speed and Moringa oleifera seed extract (MOSE) concentration and their effects on the turbidity of the surface water were established. The data obtained was fitted to a quadratic model which was also validated. The model predicted lowest turbidity of 5.49 NTU with optimal condition of 120 min of settling time, agitation speed of 100 rpm, 10 min of agitation time and 3 g/l of MOSE concentration. The condition was verified in replicates and turbidity of 5.51 NTU was obtained. The result obtained from this study could be applied to industrial scale for treatment of water. Keywords: Moringa oleifera, RSM, Surface water, Optimization, Coagulation

An optimization of the biodiesel production from a waste frying oil via a heterogeneous transesterification was studied. This present study is also aimed at investigating the catalytic ehaviour of the alumina supported eggshell (ASE) for the synthesis of biodiesel. A synthesized ASE catalyst, at various mixing ratios of alumina to eggshell, was investigated and exhibited a better activity for the reaction when the eggshell and alumina were mixed via incipient wetness impregnation in 2 : 1 proportion on a mass basis and calcined at 900 °C for 4 h. The as-synthesized catalyst was characterized by basicity, BET, SEM, EDX, and FTIR. The 2k factorial experimental design was employed for an optimization of process variables, which include catalyst loading, reaction time, methanol/oil molar ratio and reaction temperature and their effects on the biodiesel yield were studied. The optimization results showed that the reaction time has the highest percentage contribution of 40.139% while the catalyst loading contributes the least to the biodiesel production, as low as 1.233 %. The analysis of variance (ANOVA) revealed a high correlation coefficient (R2 = 0.9492) and the interaction between the reaction time and reaction temperature contributes significantly to the biodiesel production process with percentage contribution of 14.001 %, compared to other interaction terms. The biodiesel yield of 77.56% was obtained under the optimized factor combination of 4.0 wt.% catalyst loading, 120 min reaction time, 12 : 1 methanol/oil molar ratio and reaction temperature of 65 °C. The reusability study showed that the ASE catalyst could be reused for up to four cycles and the biodiesel produced under optimum conditions conformed to the ASTM standard.

This study is initiated to launch an activated carbon derived from Leucaena leucocephala seed pod as an adsorbent for the removal of hexavalent chromium from aqueous solution. The prepared activated carbon was characterized by proximate analysis, Brunauer-Emmett-Teller (BET) surface area measurement, scanning electron microscopic-energy dispersive X-ray (SEM-EDX) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The effects of various variables, initial Cr(vi) concentration, contact time, adsorbent dosage, temperature and pH, which influence the adsorption process, were investigated. Equilibrium adsorption isotherms, kinetic and thermodynamic behaviour of the process were studied. The pH at point of zero charge (pHpzc) of 5.20 suggested that surface of the activated carbon was positively charged for pH below the pHpzc, attracting anions. The obtained results showed that 100 min contact time, 1.0 g adsorbent dose, 45 °C temperature and solution pH of 6.0 resulted in maximum Cr(vi) uptake. The experimental data better fitted to the Langmuir isotherm with monolayer adsorption capacity of 26.94 mg/g. The kinetic analysis revealed that pseudo-second-order model fitted well to the acquired experimental data. The thermodynamic behaviour of Cr(vi) adsorption onto activated carbon was found to be spontaneous and endothermic in nature.

Abstract The activated carbon from Leucaena leucocephala seed shell was prepared by chemical activation, characterized and used as adsorbent for the removal of hexavalent chromium [Cr(VI)] from aqueous solution via batch mode adsorption. The variables affecting the adsorption process, initial adsorbate concentration, pH, adsorbent dosage and temperature were optimized using central composite design (CCD) of the response surface methodology (RSM) at fixed contact time of 60 min. Equilibrium adsorption isotherm and kinetic were also studied. The analysis of variance (ANOVA) revealed that all the variables studied had significant effects on the removal efficiency of Cr(VI). The obtained data showed that 71.49 mg/L initial Cr(VI) concentration, 4.22 solution pH, 0.57 g adsorbent dosage and 26.2 °C temperature resulted in 95.62% adsorption. Equilibrium adsorption isotherm and kinetic studies showed that Freundlich isotherm and pseudo-second-order kinetic model fitted well to the experimental data. The activated carbon from Leucaena leucocephala seed shell was found to be efficient for Cr(VI) adsorption.

Polymers play a significant role in enhanced oil recovery (EOR) due to their viscoelastic properties and macromolecular structure. Herein, the mechanisms of the application of polymeric materials for enhanced oil recovery are elucidated. Subsequently, the polymer types used for EOR, namely synthetic polymers and natural polymers (biopolymers), and their properties are discussed. Moreover, the numerous applications for EOR such as polymer flooding, polymer foam flooding, alkali–polymer flooding, surfactant–polymer flooding, alkali–surfactant–polymer flooding, and polymeric nanofluid flooding are appraised and evaluated. Most of the polymers exhibit pseudoplastic behavior in the presence of shear forces. The biopolymers exhibit better salt tolerance and thermal stability but are susceptible to plugging and biodegradation. As for associative synthetic polyacrylamide, several complexities are involved in unlocking its full potential. Hence, hydrolyzed polyacrylamide remains the most coveted polymer for field application of polymer floods. Finally, alkali–surfactant–polymer flooding shows good efficiency at pilot and field scales, while a recently devised polymeric nanofluid shows good potential for field application of polymer flooding for EOR.

The primary aim of this research is to synthesis composite anthill-chicken eggshell catalyst, which is characterized and employed for the synthesis of biodiesel from waste frying oil. The as-synthesized catalyst was characterized using various characterization techniques, such as X-ray fluorescence (XRF), Fourier transform infrared radiation (FTIR), Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), and Basicity. The influence of different reaction parameters on the catalytic reaction, reaction time, catalyst loading and reaction temperature in the range of 50–75°C were studied at fixed methanol/oil ratio of 6:1. The experimental data obtained showed that at reaction time of 2 h, catalyst loading of 5 wt% and reaction temperature of 60°C, the biodiesel yield was 70%. The synthesized catalyst was found to convert low-grade oil into biodiesel via a single-step transesterification process, and its activity has the potential for improvement.