Agro-industrial waste ‘wheat bran’ for the biosorptive remediation of selenium through continuous up-flow fixed-bed column

Abstract

Present study deals with the utilization of an agro-industrial waste wheat bran for the remediation of selenium species, Se(IV) and Se(VI) by continuous up-flow fixed-bed column system. Laboratory-scale column tests were performed to determine potentiality of wheat bran at various bed height, flow rates and initial metal ion concentration and it was found to be very potential biosorbent as it showed good sorption capacities of 72.54 μg/g and 62.51 μg/g for Se(IV) and Se(VI) respectively. Different models like Bed Depth Service Time (BDST), Thomas and Yoon–Nelson were applied to the experimental sorption data. The data showed very good fit to BDST model and sorption capacities ( N o) computed using BDST model were 26,664 μg/L and 26,400 μg/L for Se(IV) and Se(VI) respectively. Also Yoon–Nelson model was found to show good agreement with the experimental kinetic results as compared to the Thomas model. Wheat bran was amenable to efficient regeneration with 10% NaOH. The biosorbent retained most of its original uptake capacity over three cycles of use. The excellent reusability of the biosorbent could lead to development of a viable metal remediation technology. Life factor calculation revealed that biosorbent bed will have sufficient capacity to avoid breakthrough at time t = 0 up to 12.17 cycles for Se(IV) and 6.28 cycles for Se(VI) and bed would be completely exhausted after 56.89 cycles for Se(IV) and 18.73 cycles for Se(VI).