Adsorptive removal of lead and arsenic from aqueous solution using soya bean as a novel biosorbent: equilibrium isotherm and thermal stability studies

In this study, adsorption potential of soya bean adsorbent for lead (Pb) and arsenic (As) has been assessed in order to consider its suitability for purification of wastewater containing heavy metals. The main focus of study was on Pb and As. Batch experiments were performed to study the adsorption of Pb and As on soya bean absorbent. The effect of various experimental parameters (adsorbent dose, contact time, temperature and pH) was studied, and optimal conditions were determined. The effect of adsorbent dose on the biosorption of Pb and As from aqueous solution was studied at 37 °C by varying the adsorbent amount from 1 g/100 ml to 4 g/100 ml. Highest amount of Pb and As was adsorbed at sorbent amount of 3 g/100 ml. The optimum pH for removal of As and Pb was found to be 2.0 and 4.0 ± 0.26. Maximum biosorption of Pb and As was achieved at 37 °C. The maximum percentage removal of Pb and As was attained at 60 min of shaking time. Langmuir and Freundlich isotherm models were utilized for equilibrium studies. It was found that biosorption by soya bean adsorbent was exothermic in nature. The thermal degradation analysis suggested that the degradation occurs in two steps and adsorbent is thermally stable.