Modified agricultural wastes as potential environmental decontaminants: finding possibilities for treating cadmium contaminated waters

There is a need to find eco-friendly methods for preventing toxic heavy metals from subsuming into food chain due to their deadly impact on plants and animals. A study was employed to investigate cadmium adsorption efficiency of biowastes and their derived products. The bio-wastes included apple pomace and sawdust based vermicompost, later converted to biochar. The study elucidated the impact of changing pH, initial concentration and contact time on cadmium adsorption efficiency of biowastes. Among different adsorbents, the biochars efficiently removed Cd (II) and attained equilibrium at a faster rate. The equilibrium data best fitted to Freundlich and Langmuir isotherm. Among different adsorbents, maximum adsorption (qmax) (35.075 mg g-1) from Langmuir adsorption isotherm was reported for vermicompost derived from 100% sawdust. Among biochars highest qmax (3.0 mg g-1) was reported for biochar obtained from 100% apple pomace. All adsorption systems were exothermic, with AT values ranging from 0.05-0.75 J/mol at pH 8 and 0.118-0.485 J/mol at pH 2. The pseudo-second order kinetic model was best fit at all concentrations implying chemisorption of Cd2+ ions by bioabsorbents. The adsorption could complete in optimum time frame required for industrial application for treating contaminated water at large scale.