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

Abstract

In the present study, brick kiln slag (BKS) has been utilized for low concentration As(III) adsorption in batch mode. BKS was modified with H₂SO₄ (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 H₂SO₄ 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.