Adsorption Characteristic Study Of Fe(Ⅱ) And Mn(Ⅱ) From Groundwater Using Biosorbents

The groundwater usually contains excess Fe（II） and Mn（II） ions due to the human factors and geologicalconditions, it will seriously influence the body health of people after drinking the water. And it can also influence theproduction of industry and agriculture. This situation restricted seriously the use of groundwater and the developmentof economy. So it is urgent to develop effective method of the removal of Fe（II） and Mn（II）. The traditional methodsof removal of Fe（II） and Mn（II） from groundwater had many abuse. The cost is high and the operation is complex. Inrecent years, people take more attention to the biosorption method as its low cost, simple and convenient operation,good adsorption capability and it is friendly to the environment. So it has very important reality significance to carryout the biosotption method for the removal of Fe（II） and Mn（II） from groundwater.This study selected rice husk ash（RHA）, Saccharomyces cerevisiae（S. cerevisiae）, rice husk（RH） as theadsorbents for the removal of Fe（II） and Mn（II）. Rice husk was the by-products of rice processing and its output isvery rich. The ways of banking up and combustion not only waste the resource but also pollute the environment. Ricehusk ash was the product after combustion of rice husk. Big specific surface area and porous structure of RHA make itbecome good adsorbent material. S. cerevisiae is the product of beer brewing. It has a large production and goodadsorption capability. The three materials as adsorbents can realize the purpose using waste managed waste whileremoving Fe（II） and Mn（II） from groundwater. The contents of this paper contains the characterization of adsorbentsfor contrasting their feasibility as adsorbents, and the adsorption mechanisms. Then the influencing factors of Fe（II）and Mn（II） adsorption process were investigated via the static batch test. The isotherm and kinetics study were carriedout based on the optimal conditions. The main research results of this paper were as follows.In the matter of the characterization of adsorbents, Boehm titration method was carried out for the quantitativeanalysis of surface functional groups on the adsorbents. Results shows that the amount of alkaline groups were morethan acidic groups on the surface of RHA, RH and S. cerevisiae. And the amount of carboxyl was the most, phenolichydroxyl group was the second, the lactone base was the least. The surface functional groups were the importantactive group for the adsorption of Fe（II） and Mn（II）. Characterization of specific surface area and pore structure showsthat RHA has the biggest surface area of58.3863m2g-1, RH has the biggest average pore diameter of71.5268, andRHAhas the biggest total pore volume of0.0402cm3g-1. The sphere diameters of immobilized RHAand S. cerevisiaewere5-6mm and4-5mm, respectively. The mechanical strength of immobilized adsorbents was high and theirintegrity reached99%.The SEM analysis was carried out for the surface morphology of the adsorbents, and the surface morphology of the adsorbents can affect the adsorption of metal ions. In addition, the composition of adsorbents was analyzed by FT-IR, XRD and XRF technology. RH was mainly composed of the functional groups of cellulose and amorphous SiO₂,RHA was mainly composed of SiO₂, elements analysis also proved RHA contains large amount of Si and O. S.cerevisiae was mainly composed of saccharides and protein, and it contains—OH,—COOH, N—H functionalgroups and so on. The electrostatic adsorption and complexation happened between the surface functional groups onthe adsorbents and Fe（Ⅱ） and Mn（Ⅱ） ions. They are also the main mechanism during the adsorption process. And itcan be inferred that ions exchanged mechanism exist in the adsorption process base on the change of element contentof adsorbents.For the influencing factor analysis of the the static adsorption process, the optimal pH for Fe （Ⅱ） and Mn （Ⅱ） was5and6, respectively. The optimum adsorbent dosage of rice husk ash, S. cerevisiae, rice husk for Fe（Ⅱ） adsorptionwas0.6g/100mL,0.8g/100mL,1g/100mL, respectively. And equilibrium adsorption reaction time was obtained at50min,60min and60min, respectively. The optimum adsorbent dosage of rice husk ash, S. cerevisiae, rice husk forMn（Ⅱ） adsorption was0.8g/100mL,1g/100mL,1g/100mL, respectively. Equilibrium time of Mn（Ⅱ） adsorption wasobtained at60min.The adsorption isotherm study results show that the Langmuir equation can better fit the Fe （Ⅱ） adsorptionprocess of rice husk ash, S. cerevisiae and rice husk with the correlation coefficient R2of0.995,0.995and0.997,respectively. And the saturated adsorption amounts of Fe （Ⅱ） were6.211mg/g,4.464mg/g and4.049mg/g, respectively.The adsorption process of rice husk ash, S. cerevisiae and rice husk for Mn （Ⅱ） also fitted better with the Langmuirequation results with the correlation coefficient R2of0.9862,0.9936and0.9899, respectively. The saturatedadsorption amounts of Mn （Ⅱ） were3.016mg/g,2.229mg/g and1.899mg/g, respectively.The adsorption kinetics study results show that the pseudo-second-order kinetic model can better fit the Fe （Ⅱ）adsorption process of rice husk ash, S. cerevisiae and rice husk with the correlation coefficient R2of0.995,0.992and0.993, respectively. Similarly, the adsorption process of Mn （Ⅱ） also better fitted the pseudo-second-order kineticmodel, and the correlation coefficients R2were0.997,0.990and0.985, respectively.