Preparation Of Composite Flocculant

With the degradation of water environment,water pollution control technology is moreconcernful.And coagulation technology is the most important water pollution controltechnology, the core of coagulation technology is to reduce cost maximumly.A seires ofPolyaluminum silicate sulaftes(PASS) and Polysilicate aluminum ferric (PSAF) withdifferent conditions were prepared form bentonite through the effect of activation, acidleaching and alkali soluble and polymerization,then it modified by Polydimethyldiallylammonium chloride (PDMDAAC).Using fish water and dye water as wastewater, reactionmechanism and degradability of flocculant were studied.The results were as follows:1. the solubilization ratio of aluminium was extracted from bentonite by thermal activationof solid state using ammonium sulfate as activator. The soluble SO2was basified formleavings and polymerized silicic acid which was prepared through adjusting pH,thenPolyaluminum silicate sulaftes was prepared polymerized silicic acid and aluminium.Thetechnical condition for the activation of solid state using ammonium sulfate as activator andthe preparation of polymerized silicic acid were optimized, The Si/Al weight ratio,thebasicities,reaction temperature, reation time, dosage on turbidity removal and dye efficiencywere studied. It is found that the weight ratio of (NH4)2SO4/bentonite is2.5, activationtemperature of480℃, and activation time of2h give maximum the solubilization ratio ofaluminium. The weight ratio of NaOH/bentonite is7:5, activation temperature is480℃, andactivation time is2h. The processes for the preparation of polymerized silicie acid is that pHvalue is2(fish waste) or12(dye wastewater)，SiO2concentration is3.5%and aging time is2h.the processes of PASS were optimized:complex pH value is4, Si/Al weight ratio is1,thebasicities is1,reaction temperature and time is60℃and1h,aging time is24h and thedosage of PASS is0.5%. It could achieve83.3%of turbidity removal and achieve57.1%ofdye removal decolorization in appropriate conditions, respectively.2. Sodium carbonate was used as a activator for alkali activation of bentonite. Complex ofaluminium and ferric were found when adding acid on the primary product,then PSAF were prepared by aging. The hydrochloric acid concentration, acid leaching temperature, acidleaching time, aging time,dosage on turbidity removal and dye decolorization were studied.the optimized ratio of bentonite/Sodium carbonate is1:1.5, reaction temperature and time is850℃and2h respectively. hydrochloric acid concentration4mol/L, acid leachingtemperature100℃, acid leaching2h, pH value is4(fish waste) or10(dye wastewater),agingtime is0h and the best dosage of PSAF is1.5%. In this condition,the turbidity removal rateof fish water and the decolorization rate of dyes water is87.8%and70.3%, respectively.3. PSAF were modified by PDMDAAC organic flocculant.the pH value,the weight ratio ofbentonite/PDMDAAC,complex temperature,complex time,aging time,dosage on turbidityremoval and dye decolorization were studied.the optimized weight ratio ofbentonite/PDMDAAC is1:0.005.pH value is4(fish waste) or10(dye wastewater). complextemperature and time is60~80℃and0.5~1h,aging time is0h and the dosage ofPSAF-PDMDAAC is0.2%. In this condition,the turbidity removal rate of fish water and thedecolorization rate of dyes water is89.2%and87.7%, respectively.Using the compositeflocculant to dispose the wastewater, the degradation rate will increase, and dosage of thecomposite flocculant is only1/7equal to the inorganic flocculant which had same flocculateeffect.The result show that:high effect PASS,PSAF and PSAF-PDMDAAC were prepared fromnatural bentonite.Compared with inorganic polymer PSAF-PDMDAAC are characterized byhaving higher turbidity removal,better coagulating efficiency,lower dosage.In a word,PSAF-PDMDAAC is a high-effectiveness coagulant which has good application prospects.