Study On Preparation Of Attapulgite Modified By Heat Treatment And Organic Modifier And Removal Of Algae And Turbidity

In recent years, different degrees of algal blooms have occurred in many town, which leaded to the abundance of algal in lake.The difficulty of the plant purification process increased greatly because algae have low density, poor settlement and strong stability. A lot of researches and practical production showed that conventional water treatment process has poor effets to on removing algae and turbidity in raw water, What’s more, the conventional water treatment would increase the consumption of coagulants, disinfectants and other water treatment chemicals, which might cause the increase of residual concentration of aluminum, iron and chlorine and affected the quality of water. Meanwhile the filter was easy to be pluged by algae, which maght increased the recoil water.This paper based on traditional water treatment process, which was without adding new structures, damaging algal cells and producting pre-chlorination disinfection byproducts, attapulgite clay selected was rich source, low cost and good settlement property, and it had better adsorption, decolorization, filling property, rheological property and ion exchange properties, octadecyl trimethyl ammonium chloride (abbreviation C18) and twelve alkyl glucoside quaternary ammonium salt (abbreviation C12) were as modifler, combined heat treatment with organic modified method to prepare two kinds of modified attapulgite (refferred C18-attapulgite and C12-attapulgite). It knowned that the order of modification is organic modification after heat treatment by the appearance analysis and infrared spectroscopy (FTIR).To explore the effect of heat treatment, C18-attapulgite were analyzed by scanning electron microscope (SEM), ratio of surface area and pore size, results showed that:(1) Attapulgite by heat treatment could effectively reduce irregular needle shaped, fibrous structure;(2) Suitable process temperatures could increase the pore volume and specific surface area;(3) average pore size of C18-attapulgite calcined at200℃increased from0.871nm to1.153nm; external surface area increased from115.264m2/g to137.768m2/g; specific surface area increased from130.922m2/g to158.024m2/g.It determined by orthogonal experiments that process conditions of preparing C18-attapulgite:amount of C18and attapulgite was4g/100g, calcination temperature was200"C, modification temperature was40℃, modification time was1.0h; process conditions of preparing C12-attapulgite was amount of C12and attapulgite was6g/100g, calcination temperature was300℃, modification temperature was40℃, modification time wasl.5h.By comparing the effects of PAC combined with the unmodified attapulgite, C18-attapulgite and C12-attapulgite enhanced coagulate to remove anabaena flos aquae, scenedesmus quadricauda, algae, Mixed algae(anabaena flos aquae mixed with scenedesmus quadricauda) and turbidity, analysis was following:(1) the effects of PAC combined with three kinds of attapulgite to remove three kinds of high algae and low turbidity water were significantly better than the effect of adding PAC alone;(2) the effects of PAC combined with two kinds of modified attapulgite to removed algae and turbidity were superior to that of PAC combined with unmodified attapulgite, It could be reduced by at least40%unmodified attapulgite dosage in the case of algae removal effect was quite;(3) under equal dosage, removal effects of algae and turbidity by PAC combined with C18-attapulgite coagulation were better than that of PAC combined with C12-attapulgite, the amount of C18-attapulgite was less at a nearly removal rate, so it indicated that C18modified attapulgite was better than C12.Through studied on the optimal dosage of PAC combined with C18-attapulgite to remove anabaena flos aquae, scenedesmus quadricauda and mixed algae, and removal effects of algae and turbidity under different settling time, different pH value, different adding sequence, different hydraulic conditions, the results were as follows:(1) The algae and turbidity removal rate was above91%and82%at proper dosage of PAC combined with C18-attapulgite, and can be reduced by at least40%of the amount of PAC;(2) under same dosage of PAC and C18-attapulgite, the effect of enhanced coagulation to remove anabaena flos aquae was best;(3) The flocs of PACcombined with C18-attapulgite formed in the flocculation process were very thick, basically vertical subsidenced, the algae removal effect after settling10min was equivalent to separate dosing PAC after settling30min, greatly improved the algae and turbidity removal efficiency.(4)At different pH conditions, the algae removal effect of PAC combined with C18-attapulgite was less affected by the pH value,the optimal pH value range was wider, algae removal effect was obviously better than the alone thro wed PAC;(5) Different adding sequence, the effect of PAC combined with C18-attapulgite to remove algae and turbidity was little difference, considering a simple and convenient operation in the actual application, it suggested to add PAC and C18-attapulgite at the same time;(6) hydraulic agitation parameters required for removing different algae species by PAC combined with C18-attapulgite coagulation were not different.