Lead Desorption and Its Potential Bioavailability in Soil Used for Disposing Lead-Contaminated Pomelo Peel: Effects of Contact Time and Soil pH

Pomelo peel has been reported as an efficient biosorbent for lead removal from wastewater treatment processes. The current work aimed to examine the amounts of lead desorption from the biosorbent waste in amended soil samples for up to 3 months (10% w/w). The desorption experiments were performed under two widely used techniques, single extraction and column leaching. Lead desorption was evaluated using two common eluents, which were 0.01-M Ca(NO3)(2) and 0.04-M EDTA solutions. Under the single extraction method, using Ca(NO3)(2), the highest amounts of Pb desorption were observed at 1 month (18.0 to 33.7% of total soil Pb), followed by a decrease attributed to re-adsorption of Pb released from the pomelo waste onto the soil. Much higher percentages of the soil Pb were desorbed using the EDTA solution throughout the period of the experiment (83.5 to 110.4% of total soil Pb). Soil pH appeared to have no effect on Pb desorption at this stage. The results from the column leaching study were similar although much smaller amounts of Pb were desorbed. Sequential fractionation data indicated that the bulk of the Pb released from the pomelo waste ended up associated with the soil oxide fraction with lesser amounts associated with the soil carbonate fraction. The results of this study suggest that land disposal of lead-contaminated biowastes such as pomelo peel could release Pb by desorption into the environment. Such material should therefore be treated as Solid waste should be treated as hazardous waste and only be disposed of in safe environmentally friendly ways.

Automated summary

This study investigated the desorption of lead from amended soil samples with pomelo waste for up to 3 months using Ca(NO3)2 and EDTA solutions. Results showed higher lead desorption with EDTA solution compared to Ca(NO3)2, and soil pH did not affect lead desorption. Sequential fractionation data indicated that lead released from pomelo waste was mainly associated with soil oxide fraction.