Mohd Azmier Ahmad

Kinetics and equilibrium adsorption of iron (II), lead (II), and copper (II) onto activated carbon prepared from olive stone waste

AbstractThe adsorption of heavy metals Fe2+, Pb2+, and Cu2+ onto olive stone activated carbon (OSAC) was investigated in this study. The effects of different reaction parameters (i.e. adsorbent dosage, contact time, shaking speed, and initial pH) on the pollutant removal efficiency were determined. The adsorption processes of Fe2+, Pb2+, and Cu2+ were effectively explained using Langmuir and Freundlich isotherms. OSAC efficiently removed 99.39% Fe2+, 99.32% Pb2+, and 99.24% Cu2+ at pH 5 and with 200 rpm shaking speed. The adsorption equilibrium data were best represented by the Langmuir model, and the monolayer adsorption capacities were found to be 57.47, 22.37, and 17.83 mg/g for Fe2+, Pb2+, and Cu2+, respectively. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that OSAC can be used as a low-cost adsorbent for the treatment of wastewaters contaminated by heavy metals.

Coconut (Cocos nucifera) Shell Based Activated Carbon for the Removal of Malachite Green Dye from Aqueous Solutions

The adsorption of malachite green (MG) dye using coconut shell based activated carbon (CSAC) was investigated. Operational factors such as the effect of pH, initial dye concentration, adsorbent dosage, contact time, and solution temperature on the adsorption process were studied. Solution pH strongly affected the chemistry of both the dye molecule and CSAC in solution. Optimum dye removal was obtained at pH ≥ 8.0. Equilibrium was reached in 120 minutes contact time. The Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models were used to evaluate the adsorption data. The adsorption data fitted the Langmuir model most with maximum adsorption monolayer coverage of 214.63 mg/g. Pseudo-first-order, pseudo second-order, and intraparticle diffusion models were also used to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each model were calculated and discussed. Thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 were evaluated and it was found that the sorption process was feasible, spontaneous, and exothermic in nature. The mean free energy obtained from D-R isotherm suggests that the adsorption process follows physiosorption mechanism. The results showed that coconut shells could be employed as a low-cost precursor in activated carbon preparation for the removal of MG dye from wastewaters.

Adsorptive features of banana (Musa paradisiaca) stalk-based activated carbon for malachite green dye removal

Chemically prepared activated carbon derived from banana stalk (BSAC) was used as an adsorbent to remove malachite green (MG) dye from aqueous solution. BSAC was characterised using thermogravimetric analyser, Brunauer Emmett Teller, Fourier transform infrared spectrometry, scanning electron microscopy, pHpzc, elemental analysis and Boehm titration. The effectiveness of BSAC in adsorbing MG dye was studied as a function of pH, contact time, temperature, initial dye concentration and repeated desorption–adsorption processes. pHpzc of BSAC was 4.5 and maximum dye adsorption occurred at pH 8.0. The rate of dye adsorption by BSAC was very fast initially, attaining equilibrium within 120 min following a pseudo-second-order kinetic model. Experimental data were analysed by Langmuir, Freundlich and Dubinin–Raduschevich isotherms. Equilibrium data fitted best into the Langmuir model, with a maximum adsorption capacity of 141.76 mg·g−1. Δ G 0 values were negative, indicating that the process of MG dye adsorption onto BSAC was spontaneous. The positive values of Δ H 0 and Δ S 0 suggests that the process of dye adsorption was endothermic. The regeneration efficiency of spent BSAC was studied using 0.5 M HCl, and was found to be in the range of 90.22–95.16% after four cycles. This adsorbent was found to be both effective and viable for the removal of MG dye from aqueous solution.

Preparation of Activated Carbon From Olive Stone Waste: Optimization Study on the Removal of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from Aqueous Solution Using Response Surface Methodology

The removal efficiencies of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from aqueous solution with olive stone activated carbon (OSAC) were investigated in this paper. Central composite design method was used to optimize the preparation of OSAC by chemical activation using potassium hydroxide (KOH) as chemical agent. The optimum conditions obtained were 715°C activation temperature, 2 hours activation time, and 1.53 impregnation ratio. This resulted in removal of 99.25% Cu2+, 94.98% Cd2+, 99.08% Ni2+, 99.33% Pb2+, 99.41% Fe2+, and 99.17% Zn2+, as well as 73.94% OSAC yield. The surface characteristics of the activated carbon (AC) prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer–Emmett–Teller (BET) surface area, total pore volume, and average pore diameter of the prepared activated carbon were 886.72 m2/g, 0.507 cm3/g, and 4.22 nm, respectively. The equilibrium data of the adsorption was well fitted to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Fe2+ (57.47 mg/g), followed by Pb2+ (22.37 mg/g), Cu2+ (17.83 mg/g), Zn2+ (11.14 mg/g), Ni2+ (8.42 mg/g), and Cd2+ (7.80 mg/g). The prepared OSAC can be used for efficient removal of metals from contaminated wastewater.

Present technologies for hydrogen sulfide removal from gaseous mixtures

Abstract Natural gas, refinery gas, and coal gas contain acid gases such as hydrogen sulfide (H2S) and carbon dioxide that must be removed from the gas stream due to the toxicity of H2S and to prevent corrosion to piping and production facility caused by the acid gases. In this article, current technologies for the acid gas removal are selected and reviewed. The review includes absorption, adsorption, conversion of H2S into elemental sulfur, and membrane reactor for H2S decomposition and desulfurization. Recently, hollow fiber membrane contactor has been in the limelight of research in H2S absorption from gaseous mixture due to its potential to overcome problems such as foaming and loading. Recent trends on Claus tail gas cleanup technologies are highlighted due to the recent progress in membrane technology. The article also suggests current research on the acid gas removal technology using catalytic membrane reactor. The interest on finding suitable active component and support and studying the membrane structure for enhanced removal of acid gases is likely to be rekindled in the near future.

Adsorptive removal of a synthetic textile dye using cocoa pod husks

The adsorption of a synthetic textile dye (Remazol Brilliant Black Reactive) on cocoa pod husk-based activated carbon was investigated in batch process. The adsorbent prepared was characterized by gas adsorption surface analysis (Brunauer Emmett Teller, BET), scanning electron microscopy, and Fourier transform infrared spectroscopy. The effects of initial dye concentration, contact time, solution temperature, and solution pH were evaluated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, the first being the best with maximum monolayer coverage of 111 mg g−1. Kinetic data were fitted into pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models; the pseudo second-order model provided the best correlation. Maximum adsorption was observed at pH 7. Standard free energy, standard enthalpy, and standard entropy were also calculated. The adsorption interaction was found to be endothermic and spontaneous. Both the mean free energy of adsorption and the activation energy show that the mechanism is by physisorption.

Response Surface Modeling and Optimization of Remazol Brilliant Blue Reactive Dye Removal Using Periwinkle Shell-Based Activated Carbon

This work investigates both batch and optimization studies of adsorption of Remazol Brilliant Blue Reactive (RBBR) dye onto activated carbon prepared from periwinkle shells (PSAC). The effects of three preparation variables: CO2 activation temperature, CO2 activation time, and KOH: char impregnation ratio (IR) were studied using Response Surface Modeling (RSM). Based on the central composite design (CCD), a quadratic model and two-factor interaction models (2FI) were developed to correlate the three preparation variables to the two responses: RBBR dye removal and PSAC yield. The optimum conditions for preparing PSAC for adsorption of RBBR dye were found as follows: CO2 activation temperature of 811°C, CO2 activation time of 1.7 h and IR of 2.95, which resulted in 82.76% of RBBR dye removal and 35.83% of PSAC yield. Experimental results obtained agreed satisfactorily well with the model predictions. The activated carbon prepared under optimum conditions was mesoporous with BET surface area of 1894 m2/g, total pore volume of 1.107 cm3/g and average pore diameter of 2.32 nm. The surface morphology and functional groups of PSAC were respectively determined from the scanning electron microscopy (SEM) and Fourier transform infrared analysis (FTIR).

Removal of Remazol Brilliant Violet-5R dye using periwinkle shells

The purpose of this research is to obtain optimal processing conditions for the adsorption of Remazol Brilliant Violet-5R (RBV-5R) dye onto activated carbon prepared from periwinkle shells (PSAC) by chemical activation with KOH using response surface methodology. Central composite design (CCD) was used to determine the effects of three preparation variables; CO2 activation temperature, CO2 activation time and KOH:char impregnation ratio (IR) on two responses; percentage RBV-5R dye removal and PSAC yield. Based on the CCD, two quadratic models were developed for percentage RBV-5R dye removal and PSAC yield, respectively. The most influential factor on each experimental design response was identified from the analysis of variance (ANOVA). The optimum conditions for the adsorption of RBV-5R dye onto PSAC were CO2 activation temperature of 811 °C, CO2 activation time of 1.70 h and IR of 3.0, resulting in 81.28% RBV-5R dye removal and 28.18% PSAC yield. PSAC prepared under optimum conditions was mesoporous with a Brunauer–Emmett–Teller surface area of 1894 m2·g−1, total pore volume of 1.107 cm3·g−1 and average pore diameter of 2.32 nm. The surface morphology and functional groups of the activated carbon were respectively determined from the scanning electron microscopy and Fourier transform infrared analysis.

Adsorption Kinetic Studies for the Removal of Synthetic Dye Using Durian Seed Activated Carbon

In this study, durian seeds were chemically modified using KOH as an impregnating agent to prepare durian seed activated carbon (DSAC). DSAC was characterized using FTIR, BET, SEM, and proximate analysis techniques and used for the adsorption of Remazol brilliant blue reactive (RBBR) dye. The effects of pH, contact time, initial dye concentrations, and solution temperature on the adsorption process were investigated experimentally in batch process. Maximum dye removal was obtained at pH 2 to be 95.17%. Experimental data were analyzed using eight model equations: Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Radke–Prausnite, Sips, Viet–Sladek, and Brouers–Sotolongo isotherms and it was found that the Freundlich isotherm model fitted the adsorption data most. Adsorption rate constants were determined using pseudo first-order, pseudo second-order rate equation, Elovich, and Avrami kinetic models. The adsorption of RBBR dye onto DSAC followed pseudo second-order model and the mechanism of adsorption was controlled by both film and Intraparticle diffusions. Thermodynamic parameters such as ΔG, ΔH, and ΔS were also calculated for the adsorption process. The process was found to be spontaneous and endothermic in nature. The results indicate that DSAC is a suitable adsorbent for the adsorption of RBBR dye from aqueous solutions. GRAPHICAL ABSTRACT

Scavenging malachite green dye from aqueous solutions using pomelo (Citrus grandis) peels: kinetic, equilibrium and thermodynamic studies

AbstractActivated carbon produced from pomelo peels (PPAC) was tested for its effectiveness in the removal of malachite green (MG) dye from aqueous solution. The PPAC prepared was characterized using TGA, BET, FTIR, SEM, pHpzc, Elemental analysis and Boehm titration, respectively. The extent of dye adsorption was investigated as a function of pH, contact time, adsorbate concentration and solution temperature. Dye removal was pH dependent, resulting in 95.06% removal at pH 8.0. Quantum chemical studies suggested that the cationic MG dye possessed minimal molecular size at planar geometry coupled with high-electrostatic interaction thereby, enhancing the adsorption at high pH. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms were used to fit the adsorption data. Langmuir isotherm fit the adsorption data most with maximum monolayer adsorption capacity of 178.43 mg/g. The kinetic data fitted the pseudo-second-order model with correlation coefficient greater than 0.99. The mean free en...