Study On The Remediation Of Copper And Lead Contaminated Soil By Nano-hydroxyapatite

The amelioration effects of nano-HAP were tested under the laboratory simulation experiment and field experiment for the repair effects of Cu2+and Pb2+composite pollution. Firstly, competitive adsorption kinetics of aqueous Pb2+and Cu2+on Nano-HAP surfaces were investigated for discussed the adsorption mechanism of two kinds of heavy metal ion compound exist on hydroxyapatite surface. Secondly, compared with the change of the adsorption effect which was produced by different impact factors.Proving the adsorption mechanism of Pb2+and Cu2+on nano-HAP. In addition, different particle sizes of HAP were applied in the field demonstration, in which ryegrass (Lolium perenne L.) was planted for in-situ remediation. The effect of the soil pH, the growth of ryegrass and the form transformation of Cu2+in soil were studied. Compared with the repair effect in soil pollution of Cu2+and the repair mechanism between different particle size of HAP. The findings will provide the theory for remediation heavy metal pollution in the soil and water environment.The main research contents and the results are as follows:1. Competitive adsorption kinetics of aqueous Pb2+and Cu2+on Nano-HAP surfaces were investigated by performing the adsorption kinetics experiments and comparing the change of ζ potentials and XRD-map before and after metal adsorption. The results showed that the adsorption quantity of Pb2+on Nano-HAP was higher than that of Cu2+in the single system. However, the competitive adsorption of Pb2+and Cu2+occurred in the co-existence system of Pb2+and Cu2+. The adsorption quantity of Cu2+on Nano-HAP increased, while that of Pb2+decreased. The X-ray diffraction (XRD) and adsorption quantities of Ca2+surface analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb2+, while surface complexation and electrostatic adsorption account for Cu2+sequestration. The adsorption quantities of Pb2+and Cu2+on Nano-HAP had marked linear relationship with Ca2+release from Nano-HAP(R20.8610.954). The adsorption kinetics were fitted with the equations of first-order, second-order, parabola, Elovich, double constant equation and LJ function, respectively, in which the second-order and power function kinetics equation fitted the results best. According to above results, the adsorption kinetics of Pb2+and Cu2+on Nano-HAP is a complex adsorption processes both with chemical reaction and physical adsorption. 2. Result of adsorption isotherms of Cu2+and Pb2+on nano-HAP by different impact factors showed:Control of the pH value of the reaction system in3,4,5, the adsorption quantity of Pb2+and Cu2+were largest in pH value5. The effect of adsorption of Cu2+and Pb2+on the nano-HAP was different for Na+and Ca2+ionic strength. In low concentration of Cu2+, the adsorption quantity of Cu2+on the nano-HAP was less effect by different Na+ionic strength. In high concentration of Cu2+, high Na+ion strength (0.1mol·L-1) promoted the adsorption of Cu2+on nano-HAP. With the change of Na+ion strength, the adsorption quantity of Pb2+on the nano-HAP was ordered for0.01mo·L-1>0.1mol·L-1>0.001mol·L-1. As Ca2+ionic strength increased, saturated adsorption of Pb2+on nano-HAP was gradually lowed, but the influence of saturated adsorption of Cu2+was little. At low concentrations of Cu2+, the adsorption quantity of Cu2+on three different particle sizes of HAP was ordered for nano-HAP> micro-HAP> AP. The adsorption quantity of Cu2+on micro-HAP was significant rised, even higher than for the adsorption quantity of Cu2+on nano-HAP, with the increased of initial concentration of Cu2+. The adsorption quantity of Pb2+on three different particle sizes of HAP was ordered for micro-HAP> nano-HAP> AP. The saturated adsorption of Cu2+on Nano-HAP was35.8mg·g-1, the saturated adsorption of Pb2+was469.5mg·g-1.The competitive adsorption of Pb2+and Cu2+occurred in the co-existence system of Pb2+and Cu2+.3. In this paper, different particle sizes of HAP, including0.58%N-HAP,1.16%N-HAP,1.16%M-HAP and1.16%AP, were applied in a Cu contaminated filed, in which ryegrass(Lolium perenne L.) was planted for in-situ remediation. The results show that these amendments not only increased soil pH but also promoted the transformation of Cu from active forms to inactive ones. Judged by the biomass and Cu bioaccumulation quantity of ryegrass, these amendments had the ability to decrease Cu toxicity in soil in the order of1.16%M-HAP>1.16%N-HAP>1.16%AP>0.58%N-HAP. The biomass of ryegrass increased with the application of1.16%M-HAP. As a kind of chemical fertilizer, Phosphorus was extremely necessary for ryegrass growth in the mine tailings which came from M-HAP. The quantity of Cu bioaccumulation in ryegrass is4722milligram as1.16%M-HAP was applied. The Cu concentration in ryegrass differed in each growth stage of ryegrass. With the same treatment, Cu concentration in the aboveground part of ryegrass was higher in the first harvest than the other ones. The accumulative total concentration of Cu in the ryegrass root was more than1000mg·kg-1, which reached the standards of hyper accumulator.