Ynamic Adsorption And Desorption Of Pb(Ⅱ) And Cd(Ⅱ)from Solution By Immobilized Lentinus Edodes Residue

Recently, with the development of global industry, water pollution becomes more and more severe. Heavy metal is to endanger extremely large pollution to the ecological environment. In company with the fast development of the metal plating, mining, dying, petrochemical and battery Industries, a great deal of wastewater containing the excessive dangerous heavy metal ions has been discharged into the environment and would endanger the great harm to the environmental ecology and the human health. The objective of this study is to adsorb Pb2+andCd2+from aqueous solution by immobilized Lentinus edodes of using fixed-bed column and the desorption process of Pb2+andCd2+by immobilized L. edodes was investigated in this research.1Best condition for PVA-SA immobilizing L.edodes absorbing Pb2+and Cd2+from solution by using fixed-bed column.The important design parameters such as column bed height, flow rate of metal solution into the column and initial concentration of metal solution have been investigated.(1) The uptake of Pb2+and Cd2+increased with increase of the bed height from75to124mm. The breakthrough time was increased with an increase of the bed height too. When the bed height ranged75-124mm, the breakthrough time of Pb2+was211min,335min and460min and the breakthrough time of Cd2+was44min,87min,235min respectively, the equilibrium quantities of Pb2+was1.742mg/g,2.058mg/g and2.299mg/g and the equilibrium quantities of Cd2+was1.118mg/g,1.527mg/g,2.088mg/g.(2) With increase of flow rate of metal solution into the column, biosorption capacity by fixed-bed column minished. Suitable flow rate range was8-10mL/min for Pb2+/Cd2+biosorption. By flow rate raising from8-16mL/min, the biosorption quantity of Pb2+was reduced from2.511to0.978mg/g, while that of Cd2+was form1.579to0.579mg/g.(3) When initial heavy metal concentration enhanced from20mg/L to40mg/L, the breakthrough time of Cd2+was reduce from87min to13min, and when initial heavy metal concentration was60mg/L, the fix-bed column had breakthrough immediately. The biosorption capacity of Pb2+was higher then Cd2+, but when the initial heavy metal concentration ranged80-100mg/L, the fix-bed column biosorption capacity can not meet the requirements.(4) Pb2+restained the biosorption of Cd2+when Pb2+concentration raised from0mg/L to20mg/L and biosorption quantity of Cd2+droped (1.527-0.195mg/g). But when concomitant metal ion concentration was less than10mg/L, biosorption quantity of Pb2+increased.(5) Thomas model well fit Pb2+and Cd2+biosorption kinetics with R2of0.88-0.98.(6) BDST model BDST model was used for analysis of column performance data and the model parameters were evaluated with R2of0.9016for Cd2+and0.9998for Pb2+at breakthrough time,0.9966for Cd2+and0.9977for Pb2+at service time.2Best condition for desorption of Pb2+and Cd2+from PVA-SA immobilizing L.edodes.The important parameters such as the sort of desorbent, equilibrium time and concentration of desorbent have been investigated.(1) Among6kinds of desorbent (H2SO4, HNO3, HC1, Na2CO3, NaHCO3, NH4C1), HCl and HNO3could desorp Pb2+and Cd2+, but HCl was more suitable for desorption.(2) By using HCl to desorp Cd2+and Pb2+, the equilibrium time was60min and90min respectively. Pseudo-Second-Order model fit Cd2+and Pb2+desorption kinetics well with R2of0.9989and0.9969respectively.(3) As concentration of HCl increased, desorption ratio of Cd2+and Pb2+raised. The desorption efficiency of Cd+and Pb+reached maxmium when concentration of HC1was0.1and lmol/L respectively.(4) After three times of regeneration by using HCl, Cd2+and Pb2+biosorption ratios by PVA-SA immobilized L.edodes still reached85.24and69.07%separately.3Scanning electronic microscope (SEM) and energy spectrum observation.According to scanning electronic microscope (SEM) observation:after absorption, Pb2+/Cd2+crystal was found on PVA-SA immobilized L.edodes, as well as surface of PVA-SA immobilized L.edodes beads became close-grained. Because cadmium crystal was smaller than lead crystal, surface of PVA-SA immobilizing L.edodes after absorbing Cd2+was more close-grained than the one after absorbing Pb2+...