Application of Chemically Modified Industrial Slag to As(III) Adsorption from Wastewater: Kinetics and Mass Transfer Analysis

In the present study, brick kiln slag (BKS) has been utilized for low concentration As(III) adsorption in batch mode. BKS was modified with H 2 SO 4 (SA) and NaOH (SB) for enhancing As(III) uptake capacity. Maximum adsorption capacity (13.7 mg/g ) was observed for SA at 298 K, pH = 7.0, adsorbent dose = 0.3 g and time = 70 min which was 1.4 times higher than that of SB. Adsorption data modelled into Freundlich isotherm and pseudo-second-order kinetics. Mass transfer coefficients decreased with increase in As(III) concentration. Film diffusion significantly dominated the adsorption of As(III) ions irrespective of the initial concentration. Dimensionless Sherwood number ( Sh ) interrelated As(III) concentration ( C o ) as: Sh = 2.97(C o ) –0.376 , Sh = 4.12(C o ) –0.215 , Sh = 4.83(C o ) –0.588 for H 2 SO 4 modified, NaOH modified and native slag respectively. Low temperature (298 K) favoured As(III) adsorption (based on ∆G° value). Therefore, the modified slag can be used as an effective adsorbent for As(III) remediation from groundwater.