Adsorption Studies of Volatile Organic Compound (Naphthalene) from Aqueous Effluents: Chemical Activation Process Using Weak Lewis Acid, Equilibrium Kinetics and Isotherm Modelling

This study deals with the preparation of activated carbon (CDSP) from date seed powder (DSP) by chemical activation to eliminate polyaromatic hydrocarbon—PAHs (naphthalene—C10H8) from synthetic wastewater. The chemical activation process was carried out using a weak Lewis acid of zinc acetate dihydrate salt (Zn(CH3CO2)2·2H2O). The equilibrium isotherm and kinetics analysis was carried out using DSP and CDSP samples, and their performances were compared for the removal of a volatile organic compound—naphthalene (C10H8)—from synthetic aqueous effluents or wastewater. The equilibrium isotherm data was analyzed using the linear regression model of the Langmuir, Freundlich and Temkin equations. The R2 values for the Langmuir isotherm were 0.93 and 0.99 for naphthalene (C10H8) adsorption using DSP and CDSP, respectively. CDSP showed a higher equilibrium sorption capacity (qe) of 379.64 µg/g. DSP had an equilibrium sorption capacity of 369.06 µg/g for C10H8. The rate of reaction was estimated for C10H8 adsorption using a pseudo-first order, pseudo-second order and Elovich kinetic equation. The reaction mechanism for both the sorbents (CDSP and DSP) was studied using the intraparticle diffusion model. The equilibrium data was well-fitted with the pseudo-second order kinetics model showing the chemisorption nature of the equilibrium system. CDSP showed a higher sorption performance than DSP due to its higher BET surface area and carbon content. Physiochemical characterizations of the DSP and CDSP samples were carried out using the BET surface area analysis, Fourier-scanning microscopic analysis (FSEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform spectroscopic analysis (FTIR). A thermogravimetric and ultimate analysis was also carried out to determine the carbon content in both the sorbents (DSP and CDSP) here. This study confirms the potential of DSP and CDSP to remove C10H8 from lab-scale synthetic wastewater.

Biosorptive Removal of Hexavalent Chromium from Aqueous Industrial Solutions by a Novel Wood Apple Shell Powder Biomass

A novel wood apple shell powder (WASP) biomass was used to remove Cr(IV) from aqueous solutions. Study revealed that WASP removed 50 mg/l of Cr(VI) with >99% efficiency. Optimum parameters for maximum biosorption were: pH 2-4, contact time 60 min and biomass quantity 1g/10 ml. Interestingly, it was observed that loading capacity of WASP was higher as compared to conventional activated charcoal. Equilibrium sorption capacity of WASP increased with increasing initial concentration of Cr(VI) from 5-300 mg/L. Biosorption by WASP conformed to the Langmuir and Freundlich adsorption isotherms. Desorption of Cr(VI) took place with >80% efficiency. Continuous mode study in packed bed column showed that WASP has immense potential as “biomaterial” for the removal/recovery of Cr(VI) from aqueous industrial solutions.