Preparation Of Magnetic Absorbents With Microorganism And Their Characteristics On The Heavy Metals Wastewater Treatment

Heavy metals are major pollutants in the mining, smelting, metal processing andother industrial activities. They not only cause water imbalance, but also canaccumulate in the human body through the food chain to endanger human health.Heavy metals wastewater can be disposed by chemical precipitation, ion exchange,membrane separation. But there are some disadvantages such as high operating costs,does not apply to low-strength wastewater and other issues. Biosorptions, as anemerging technology, has been considered as an alternative method of wastewatertreatment, especially for those with low concentration of heavy metals for takingadvantage of their chemical structure and composition characteristics to adsorption ofheavy metal ions.So in this study, sawdust was selected to made magnetic biological carrier bychemical coprecipitation method. Then magnetic biological carrier was combinedwith pseudomonas putida or escherichia coli through immbolization method. Afterfreeze-dried, magnetic absorbents with microorganism was be made. These magneticabsorbents with microorganism was analyzed by SEM, BET, XRD and the dosage ofdissolution ferrum was measured during application in acidic solution. Theadsorptiom properities of magnetic absorbents with microorganism toward Cd2+wereevaluated. Various factors, which affected the uptake behavior, such as contact time,pH, initial concentration of Cd2+ion and adsorbent dosage, were investigated. Themechanism of magnetic absorbents with microorganism adsorbing Cd2+were studied.The main conclusions in this study have been summarized as follows:(1) Compared with raw sawdust, modification and magnetically modificationmade the surface area increased from9.854m2/g to35.566m2/g and pore sizeincreased from5.33nm to24nm. But after microorganism immbolization the surfacearea and pore size decreased，the surface area and pore size of magnetic absorbentswith pseudomonas putida were23.787m2/g and21.56nm， and magnetic absorbentswith escherichia coli were21.168m2/g and15.37nm.(2) The removal rate increased with the increasing of pH in the range of2-8.During the first40min, adsorption rate was fast, then adsorption tended to balance. Atroom temperature with initial pH, the maximum adsorption capacity of Cd2+on raw sawdust, modified sawdust, magnetic sawdust, magnetic absorbents withpseudomonas putida and magnetic absorbents with escherichia coli was3.75mg/g,14.883mg/g,15.309mg/g,20.727mg/g and20.653mg/g respectively.(3) Adsorption process of magnetic absorbents with microorganism for Cd2+wasthe results of physical adsorption, ion exchange and surface complexation.(4) The adsorption isothermal data of Cd2+on these sorbents could be interpretedthe Langmuir and Freundlich equations. The dates fited the secondary dynamic modeland the correlation coefficient of raw sawdust reached above0.95and the rest reachedabove0.99. The theoretical value and the actual value of the adsorption capacity wasalso relatively close.