| Wastewater containing arsenic from extensive sources is difficult to remove,and endangers seriously the public health.Arsenic is a toxic substance,which toxicity related to its valence state.The toxicity of As(?)is the highest than As(?)and elemental As.Recently,traditional methods including precipitation,oxidation method and biological method,etc,can not meet the increasingly stringent enviromental requirements in Chilla.Large amount of spent grain has been produced by beer industry in our country every year,which is only be burnt or poultry feed.In order to solve the problems of depth removal the water containing low concentration of As(?),the brewing industry waste spent grain was chosen as raw materials to prepare an effective adsorbents.Via modem analysis the composition and structure of spent grain from three different places was detemined.The main component of spent grain are cellulose,hemicellulose and lignin,in which the main element are C and O.It can be found that spent grain is rich in hydroxyl and carboxyl,which can participate in the adsorptional activity of oxygen containing functional groups and to enhance its adsortion cpacity.Spent grains was modified by compounds containing methanol,ethanol,acetic acid,cationic PAM,anionic PAM,non-ionic PAM,ethylenediamine,mercaptoacetic acid,respectively.Then the structure characteristics of the modified spent grain are analyzed by means of modern test methods to study the structure-activity relationship between the different groups and arsenic removal.Based on hydroxyl,amide,amino modified spent grains treatment arsenic water were researched,this paper chosen carboxyl,thiol compounds on modification spent grains.The modified spent grains by acetic acid have certain adsorption effect on adsorption of As(?).The optimum adsorption conditions for As(?)-containing water by acetic acid modified spent grains are pH 7,dosage 8 g/L and reaction time 1h.The adsorption behavior for As(?)by acetic acid modified spent grain adsorbent conformed to the pseudo-second order kinetics equation and the Freundlich adsorption model.And the adsorption reaction in the test temperature range is spontaneous,in which the k value of adsorption model parameters increased with the increase of reaction temperature,illustrated that the rise in temperature increases the adsorption intensity.The adsorption effect on adsorption of As(?)by mercaptoacetic acid modified spent grain adsorbent is much higher than that of acetic acid modified spent grains adsorbent.The optimum adsorption conditions by mercaptoacetic acid modified spent grains are pH 7,dosage 4 g/L and reaction time 1h.The adsorption behavior for As(?)conformed to the pseudo-second order kinetics equation and the Langmuir adsorption model.The adsorption reaction in the experimental temperature range is spontaneous exothermic process,in which the amount of saturated adsorption monolayer value(qm)increased with the increase of reaction temperature,illustrated that elevated temperature is conducive to the adsorption reaction.The calculated theoretically value(0.2022 mg/g)by the pseudo-second order kinetics equation coincides better with the experimental values(0.1982 mg/g).The structure-activity relationship of modified spent grains were researched.Compared with spent grain,it was found the structure topography on the surface of the modified spent grains and appears more fold,groove.FT-IR analysis showed that at the main vibration absorption peak strength of 3425?2927?1656?1039 and 610(cm-1)on modified spent grains was stronger than that of the spent grain.The most obvious was mercaptoacetic acid on modified spent grains adsorbent.The physical and chemical structure characteristics of modified spent grains affect the adsorption of As(?).Modified agent containing different functional groups modifying spent grain can cause the different properties of the specific surface area,and then the As(III)water adsorption effect is also different. |
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