Biosorption of Mercury from Dilute Aqueous Solutions Using Soybean Hulls and Rice Hulls

Abstract

This research investigated the mercury biosorption potential of soybean hulls and rice hulls from dilute aqueous solutions. Both hull types were mixed with mercury solutions. Samples were tested unaltered, and after being treated with 10 % HCL. Additional parameters tested include sample dose, contact time, particle size, mixing temperature, and the concentration and pH of the mercury solutions. Desorption studies were also performed. In addition, tests were done to determine if the hulls could be reused for mercury biosorption. The results of this study indicate that both hull types work extremely well at biosorbing mercury from dilute aqueous solutions (71–99 % removal). The parameters that resulted in higher mercury removal for both hull types include HCL treatment, higher sample dose, contact time, and lower pH. Particle size did not have a significant impact on the percent of mercury removed for both hull types. Varying the mixing temperature did not affect the soybean hulls’ mercury extracting capacities. However, increasing the mixing temperature caused the rice hulls’ mercury removal capacity to increase slightly. As the mercury solution concentration was increased, the soybean hulls’ mercury biosorption capacity increased as well. Mercury solution concentration had a minimal impact on the rice hulls’ mercury biosorption capacity. The desorption results demonstrate that it may be possible to recover some of the removed mercury (up to 41 %). The results also demonstrate that both hull types can be reused for additional mercury biosorption cycles. Hence, they may be reused over and over and do not become a hazardous waste disposal problem.