Removal Of Heavy Metals In Soil And Water By Spent Mushroom Substrates

Heavy metal pollution has been a serious environmental problem for decades. In order to explore effective methord to remove heavy metals, experiments were carried out using spent mushroom substrates ?SMS? of Lentinus edodes, Flammulina velutipes and Pleurotus ostreatus as materials to adsorb Cr³⁺, Cd²⁺ and Pb²⁺ from aqueous solution and soil. For the heavy metal pollution in aqueous solution, the effects of factors such as time, pH, dosage, initial concentration and the size of spent substrate on the adsorption were studied. After detecting and evaluating the concentrations and pollution levels of Cr³⁺, Cd²⁺ and Pb²⁺ in the soil, which sampled from batteries production region, the pollution in soil was studied based on the experimental condition set by the results of aqueous solution. The main results were as follows:1) The maximum removal rates of Cr³⁺, Cd²⁺ and Pb²⁺ in aqueous solution using Lentinus edodes SMS were 60%,76% and 82%, respectively. The adsorption kinetics conformed to a quasi-second-order kinetic model. Langmuir model can describe the adsorption of Cd²⁺ and Pb²⁺ quite successfully, while the adsorption of Cr³⁺ can be described by Freundlich model in isothermal adsorption models.2) SMS of Flammulina velutipes performed the best among these three kinds of SMS. The maximum removal rates of Cr³⁺, Cd²⁺ and Pb²⁺ in aqueous solution by SMS of Flammulina velutipes were 80%,98% and 94%, respectively. The adsorption kinetics of Cr³⁺, Cd²⁺ and Pb²⁺ can be accurately described by a quasi-second-order kinetic model. Langmuir model can describe the adsorption of Cd²⁺ and Pb²⁺ well, and the adsorption of Cr³⁺can be described by Freundlich model.3) The maximum removal rates of Cr³⁺, Cd²⁺ and Pb²⁺ in aqueous solution using Pleurotus ostreatus SMS were 74%,83% and 93%. The adsorption kinetics accorded with the quasi-second-order kinetic model. The adsorption of Cr³⁺, Cd²⁺ and Pb²⁺ can be described by Langmuir model.4) Heavy metal concentrations in the batteries production region showed varied degrees of pollution. The concentrations of heavy metal in soil were as follows:Cr³⁺,53.691 ± 10.392 ?37.743-68.248? mg/kg; Cd²⁺,1.040 ± 0.826 ?0.336-2.473? mg/kg; Pb²⁺,95.394 ± 95.285 ?27.718-299.388? mg/kg. The pollution of Cd²⁺was quite serious in this area and Pb²⁺ concentration played a major role on environmental pollution in some functional areas.5) SMS of edible fungi were used to remove heavy metals in the soil, the maximum removal rates of Cd²⁺ and Pb²⁺ were 29.79% and 81.17% by Flammulina velutipes SMS, and the best removal efficiency of Cr³⁺ was obtained by Pleurotus ostreatus SMS, with the removal rate of 50.69%.