Bengal Gram Seed Husk as an adsorbent for the removal of dye from aqueous solutions – Batch studies

Abstract

The feasibility of using Indian Seed Husk of Bengal Gram (Scientific Name: Cicer arietinum) (SHBG), abundantly available in and around the Kurnool in Andhra Pradesh, for the anionic dye (Congo red, CR) adsorption from aqueous solution, has been investigated as a low cost and an eco-friendly adsorbent. Adsorption studies were conducted on a batch process, to study the effects of contact time, initial concentration of CR, de-sorption and pH. Maximum colour removal was observed at lower pH. The dye attained equilibrium approximately at 1, 1.5, 2 and 2.5 h for dye concentrations 25, 50, 75 and 100 mg/l respectively. The present dye removal decreased from 89% to 74% as the dye concentration has been increased from 25 mg/l to 100 mg/l. A maximum removal of 92% is obtained at lower pH. Adsorption decreases with increase in pH. Maximum de-sorption of 26.4% is achieved in water medium at pH 11.95. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms. The data fitted well with the Langmuir model, with a maximum adsorption capacity of 41.66 mg g−1. The pseudo-second-order kinetics was the best for the adsorption of CR, by SHBG with good correlation. The results suggest that SHBG is a potential low-cost adsorbent for the CR dye removal from synthetic dye wastewater.