Impacts Of Organic Matter In The Red Soil Weathered From Sandstone On The As(?) Removal From Water

With the rapid development of economy,the influence of arsenic pollution on human becomes more and more obvious.Therefore,treatment of the arsenic pollution attracts more and more Chinese and foreign science researchers' attentions,especially arsenic removal material.Finding one kind of low-cost and high-benefit adsorbent is of significant realistic sense.The weathered soil of red sandstone has good effect of arsenic removal,but its effect is greatly influenced by soil organic matter.Therefore,this paper mainly focuses on the effects of organic matter on the adsorption effect of soil.Based on the analysis of physical and chemical properties,single factor impact test,dynamic analysis,five-step extraction method were employed to explore the effects of soil organic matter on arsenic removal.The main findings are as follows:(1)The adsorption of arsenic by the studied raw soil sample is significant,and the removal efficiency of arsenic can achieve more than 90%.Comparatively,the arsenic removal efficiency of the treated soil sample were better.Under the conditions of different temperature,pH value,reaction time and so on,the removal efficiency increased by 2%-7%after removing the organic matter.(2)The kinetics experiments showed that the treated soil sample had higher adsorption rate at the initial stage of adsorption,but when the adsorption equilibrium was reached,the total arsenic adsorption amount was roughly the same as that of the raw soil.It is believed that the high active organic matter like humic acid and fulvic acid in the soil sample played a inhibition role in the process of arsenic adsorption,while this kind of organic matter was gradually oxidized or decomposed by microorganisms with the reaction time going on,and finally it only showed the change of adsorption rate.(3)Desorption test results showed that the main components in the soil sample to adsorb arsenic was iron and manganese oxides and organic matter,which was the main components to absorb arsenic.(4)The influence of organic matter on arsenic adsorption can be mainly summarized into two aspects.Firstly,the organic matter can increase the total adsorption amount of of the soil.Secondly,the organic matter decreases the adsorption rate of arsenic during the adsorption process.This is caused by different kinds of organic matter.The organic matter in the soil can be classified into two categories.One is the small molecule active organic acid,mainly represented by humic acid and fulvic acid,which are chemically active and the molecular groups of which is consistent with the charge type of arsenate.Both of them have a positive charge,which can compete with the arsenate adsorption site by covering the adsorption sites on the soil surface,and thus reduce the adsorption rate of arsenic in the soil.However,due to their active chemical property,oxygenolysis happens slowly in the adsorption process to return the adsorption sites once possessed.Another is the macromolecular organic matter like humin,which can bind tightly with the soil particles,and form a gel,providing sites for arsenic adsorption and increasing the overall adsorption efficiency.