米渣蛋白对镉的吸附效果及其对土壤中镉的钝化作用研究

为探究米渣蛋白对水溶液中镉的吸附效果及米渣对土壤中镉活性的钝化效果,该研究首先用米渣蛋白在水溶液中对镉进行吸附、用盐酸解吸,并用Langmuir、Freundlich等温吸附方程来拟合米渣蛋白在水溶液中对镉的吸附过程,用动力学方程研究米渣蛋白与镉结合的机理,并根据线性关系从准一级、准二级吸附动力学方程中筛选更接近吸附动力的拟合方程。其次,通过周期取样,用Tessier分步连续提取法测定并探究米渣对土壤中镉的钝化能力。研究结果表明:在不同初始质量分数的镉溶液中米渣对镉的最大吸附量13.28mg/g,用盐酸解吸各初始质量分数下结合的镉,解吸率均达到90%以上。同时,Langmuir和Freundlich等温方程均能拟合米渣蛋白在水溶液中对镉的吸附过程,且R2达到0.99以上;准一级动力学、准二级动力学方程拟合结果是,拟合出的准二级动力学方程线性更好,米渣蛋白对镉的吸附动力更符合准二级动力学方程。土壤中镉钝化试验表明:加入米渣后,28d内土壤中镉的钝化效果较好,可能是由于米渣中的蛋白改变了土壤中镉的存在状态并降低镉的活性所致。该研究结果为米渣的应用提供新的思路,可为其在废水除镉、镉污染土壤的修复等方面应用提供理论依据。

Adsorption of cadmium in aqueous solution and passivation of cadmium in soil by rice dreg protein

Heavy metal cadmium waste is easily discharged into the environment along with waste water and waste residue. Cadmium will eventually enter the human body along with the food chain. It is difficult to be degraded in the human body, which will cause various diseases to human. However, research has shown that reducing effective cadmium content in soil can reduce cadmium content in crops. So the sufficient source and cheap material is needed to bind cadmium and reduce plants absorption cadmium. In order to explore the adsorption effect of rice dreg protein on cadmium in aqueous solution and the passivation effect on cadmium activity in soil through rice dreg. Firstly, the cadmium in aqueous solution was adsorbed by using the dreg protein, then, desorbed with the hydrochloric acid. The Langmuir and Freundlich isotherm adsorption equations were used to fit the adsorption process of cadmium in aqueous solution by using rice dreg protein, and the kinetic equations were used to fit the power of rice dreg protein combined with the cadmium. The fitting of the adsorption process was selected from the quasi-first-order and quasi-secondary adsorption kinetic equations according to the linear relationship closer to the adsorption process. Secondly, through the periodic sampling, Tessier step-by-step continuous extraction method was used to determine and investigate the ability of rice dreg to passivate cadmium in soil. The results showed that in the cadmium solution with different initial mass fraction, the maximum adsorption capacity of rice dreg to cadmium was 13.28 mg/g, and the combined cadmium desorption rate was desorbed with hydrochloric acid reached more than 90%. Simultaneously, both Langmuir and Freundlich isothermal equations can fit the adsorption process of rice dreg protein in cadmium aqueous solution, and the R2 was above 0.99 for both equations. Moreover, contrast with quasi-first-order kinetics equations, the adsorption of cadmium by rice dreg protein in solution was fitted by the pseudo-second-order kinetic equation in line. In addition, the cadmium passivation test showed better effect in soil after adding rice dreg within 28 days, which may be due to fact that the form of cadmium were changed in the soil and the cadmium activity was decreased by rice dreg protein. It was simpler to operate for rice dreg than straw in cadmium adsorption in aqueous solution, and the amount of addition was small. The addition of 0.5% and 1% rice dreg changed the state of cadmium in the soil and changed the cadmium from an active exchangeable state to an inactive state. In the passivation of cadmium in soil, the rice dreg had higher passivation rate than that of the commercial organic fertilizer, and its cost was low. Rice dreg was an environmentally friendly material. The rice dreg in the passivated cadmium in soil had the advantages of comprehensive action mechanism, simple operation, good passivation effect than that of plant straw and no pollution to the environment. Therefore, this study provided some new ideas for the application of rice dreg, such as removing cadmium from wastewater and decreasing cadmium activity in soil. Thereby it reduced cadmium in crops that planting on contaminated land or irrigation with cadmium wastewater.