Study On Preparation Of CTMAB Modified Fly Ash And Its Adsorption Ability

In this paper, CTMAB modified fly ash with high adsorption property wasprepared with cetyl trimethyl ammonium bromide (CTMAB) as a modifier and fly ashas the main raw material. The adsorption properties of modified fly ash such asadsorption thermodynamics and kinetics were studied in the course of treating mixeddye wastewater (acid dyes and reactive dyes).The characterization of solidifiedsorbent particles was studied with means of scanning electron microscopy.The factorssuch as flow velocity、pH and running time which influence the adsorption effect inthe dynamic experiment process were studied in the course of treating simulated dyewastewater and actual dyeing wastewater.And the preliminary exploration ofadsorbent recycling was carried out in order to save cost.After experimental study, the best conditions of fly ash modification weredetermined: the concentration of CTMAB is1.5g/L, pH is2, stirring time is30min,and stirring temperature is35-40℃. The dosage is the greatest treatment effect in thecourse of treating simulated dye wastewater with modified fly ash, followed by theinitial pH of wastewater, reaction temperature and reaction time. When theconcentration of simulated wastewater is200mg/L, the dosage of modified fly ash is20g/L, the initial pH of wastewater is8, the reaction temperature and time are20℃and30min respectively, COD removal rate and percentage of decolority are78%and92%.The adsorption isotherm studies of modified fly ash adsorption process show thatthe goodness of fit R~2is close to1with Freundlich isotherm equation, which has agood linear correlation; while the linear correlation of Langmuir isotherm equation ispoor. Freundlich model is well described the adsorption isotherm of dye molecules onCTMAB modified fly ash. The adsorption thermodynamic studies show that theadsorption process of CTMAB modified fly ash would belong to one kind ofexothermic reactions, which is conductive to adsorption at low temperature. Thekinetics studies of modified fly ash adsorption process show that the fitting linearcorrelation of the primary adsorption kinetic equation is better than the secondarykinetic equation. The fitting correlation coefficients of the primary and secondaryadsorption kinetic equation are0.994and0.915respectively.The best mass ratios of preparation of modified fly ash solidified particles wereas follows: modified fly ash: sodium hydroxide: sodium silicate: water: aluminumpowder=200:8:16:10:0.35. When the particle size of modified fly ash is3mm, thedrying temperature is60℃, the drying time is12h, the best COD removal rate canreach80.5%.The best operating conditions were determined in the course of treatingsimulated dye wastewater with dynamic experiment: flow velocity is45L/h, pH is6, and the running time is10h. When the actual dyeing wastewater was treated after7h,COD removal rate and percentage of decolority can reach57%and74%respectively.When adsorbing saturated solidified particles were recycled with hydrogen peroxidesolution as oxidant, it is found that the treatment effect of dye wastewater with theparticles of being recycled twice is still ideal; COD removal rate can reach54%.