Chromium (VI) adsorption from steel industry wastewater using biomass and agro-based adsorbents: A Review

Abstract

In recent years, increased steel production has resulted in an increased release of Cr (VI) effluent from electroplating processes. The current conventional technologies for Cr (VI) removal, for instance, chemical precipitation, ion exchange, membranes, and electrochemical technologies, have proven to be expensive and not eco-friendly. Adsorption using biomass or agro-based adsorbents has been demonstrated to be an eco-friendly method. In this study, the potential of several biomass and agro-based adsorbents for Cr (VI) removal from steel industry wastewater has been reviewed. The application of adsorption parameters, isotherms, and kinetic models has also been reviewed. The study review reveals that the maximum adsorption of Cr (VI) ions from wastewater was dependent on the pH, temperature, contact time, type of adsorbent material, and initial metal concentration. The literature review demonstrated that maximum Cr (VI) adsorption efficiency ranged from 90–100%, with optimum pH, contact time, and temperature ranging from 2–5, 30-180 min, and 25–30 °C, respectively. The equilibrium adsorption data was best described by the Langmuir and Freundlich isotherms and the pseudo-second-order kinetic model. The thermodynamic studies revealed that the adsorption process was spontaneous and endothermic. It has been found that biomass and agro-based adsorbents are potentially eco-friendly alternatives for Cr (VI) removal from industrial wastewater. However, several gaps have been identified to improve the Cr (VI) removal efficiency, spent adsorbent reuse and safe disposal, optimisation, and commercial application of agro-based adsorbents.