Sorption Characteristics of Halogenated Acetonitriles (HANs) in Surface Water onto Activated Carbon Prepared from Walnut Shell

Abstract

Sorption efficiencies of activated carbon prepared from walnut shell for the removal of Halogenated Acetonitriles (HANs) from surface water was investigated in this study, as an ethically sound-way of utilizing this unexploited abundant natural resource, and was also compared with burgoyne commercial activated carbon (BCAC). Major HANs created during the disinfection process consist of dichloroacetonitrile (DCAN) and bromoacetonitrile, (BCAN). Physicochemical properties of both raw and chlorinated water were determined using standard methods, and concentration of DCAN were determined from water treatment plant at different stages of treatment using High Performance liquid Chromatography (HPLC). Recovery experiments were carried out to validate experimental procedure. Batch adsorption experiments were carried out and different parameters such as adsorbent dosage (0.2, 0.4, 0.8 g), contact time (30, 60, 90 minutes), pH (5, 7, 9), and concentration (0.006 mg/L, 0.009 mg/L and 0.012 mg/L) were optimized for removal of DCAN using walnut shell activated carbon (WSAC). Experimental sorption data from different initial concentrations of DCAN were used to test conformity with Freundlich and Langmuir adsorption isotherms. Percentage recovery from experimental procedure is 86.01±0.62 to 100.0±0.00 for DCAN. Mean percentage adsorption efficiencies for simulation experiment is 16.670±0.467 to 41.67±1.103 for DCAN. Optimum conditions for DCAN were 0.8g adsorbent dosage, 60 minutes contact time, pH 9 and 0.012 mg/L initial concentration. Optimum values of theses parameters used for adsorption of DCAN in raw and chlorinated water serving the treatment plant gave an adsorption efficiency of 69.00±1.43% and 79.00±0.03 respectively. Adsorption efficiency of BCAC gave 94.4±0.42 and 98.00±1.41 for raw and chlorinated water respectively, with a total decrease in all physicochemical parameters examined after adsorption experiment. Adsorption isotherm studies indicated that Langmuir model was more suitable for the experimental data than Freundlich isotherm model. Conclusively, the effective adsorbent properties displayed by WSAC in the removal of DCAN indicate its potentials in treatment of water contaminations.