Reusability of Fe-modified MMT nanomembranes and the retrieval of the adsorbed mercury metal

Determining the applicability of a wastewater treatment procedure is dependent on its efficiency and cost-effectivity. The main objective of this study is to establish the reusability of Fe-modified MMT nanomembrane when utilized as adsorbent material for wastewaters containing mercury in complex with cyanide in aqueous solutions. Three cycles of adsorption-elution runs were done on the nanomembranes and the mercury (Hg) concentrations in the wastewaters (initial, after adsorption, after elution) were analyzed using HD XRF. Results showed that there was no substantial difference in the adsorption efficiencies for the first two (2) cycles (37.61% and 35.69%). Using 0.01M acetic acid as eluate, the nanomembranes were observed to be reusable twice before the nanomembranes become extensively degraded. In addition, precipitation was employed to retrieve the Hg from the eluates. One (1) g as-received and grinded (150–500μm) sodium thiosulfate (Na₂S₂O₃) precipitants were used and it was established that, after 24 h, the precipitant with finer particle sizes was able to retrieve higher amounts of Hg (as-received:59% vs grinded:87.27%). Moreover, increasing the amount of the grinded Na₂S₂O₃ to 5g resulted to better Hg recovery (89.47%). Further analysis on the derived precipitates also confirmed the presence of Hg (19.90ppm for red precipitates; 24.73ppm for black precipitates). (paper)