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Studies On Treatment Of Industrial Wasterwater Containing Lead Ions By Adsorption-ultrafiltration Process

Posted on:2015-02-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y Z Z OuFull Text:PDF
GTID:2181330452957832Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Chitosan was used as the adsorption agent. Based on the theoretical research of theadsorption of lead ion on chitosan, effects of various operating parameters on the removalpercentage of lead ion have been studied systematically. Then, the integrating technologies ofprecipitation-ultrafiltration and adsorption-ultrafiltration were carried out to remove lead ionfrom industrial wastewater. Further, the cleaning of ultrafiltration membrane was studied.1. Effects of chitosan dosage, pH value and temperature on the removal percentage oflead ion were investigated. Then, the adsorption kinetics and thermodynamics were alsostudied. Results showed that, the adsorption equilibrium data were fitted well by theLangmuir isotherm model. The kinetic data were fitted well by the pseudo second-ordermodel. The thermodynamic parameters indicated that the adsorption of lead ion on chitosanwas an endothermic and spontaneous process.2. Effects of temperature, pH value and adsorption agent dosage on the removalpercentage of lead ion were investigated from industrial wastewaters. Three factors threelevels orthogonal experiment was carried out and the optimal experimental conditions wereobtained. Results showed that, when the concentration of lead ion was57.5mg/L in theindustrial wastewater, the optimal operating parameter was pH value of5.0, temperature of45℃and chitosan dosage of10mg. The performance of the chitosan was steady.3. Sodium hydroxide was used as the precipitation agent. A polysulfone ultrafiltrationmembrane with the molecular weigh cut off of50000Da was employed. Effects of pH value,temperature and pressure on the rejection ratio of lead ion (R) and membrane flux wereinvestigated in detail. Results showed that, R value reached95%at pH=9-10. R valuedecreased and then increased with increasing temperature. With increasing pressure, R valuedecreased slightly, and membrane flux increased gradually.4. The polysulfone ultrafiltration membrane with the molecular weigh cut off of50000Da was used for the process of adsorption-ultrafiltration. Effects of the loading ratio ofchitosan/lead ion and pH value on R value and membrane flux were studied. Results showedthat, when the loading ratio increased from2to4, R value increased gradually and membraneflux decreased slightly. After the loading ratio reached4, R value did not change andmembrane flux decreased with the loading ratio. When pH value increased from2to7, Rvalue increased significantly and membrane flux decreased gradually. After pH value reached7, effect of pH value on R value was slight, and membrane flux decreased gradually.5. The ultrafiltration membrane was cleaned by using three modes (the washing ofhydrochloric acid, the washing of sodium hydroxide and the washing of ultrasound). Resultsshowed that, the chemical washing increased slightly membrane flux, and did not make theflux of fouling membrane reach the flux of new membrane. The washing of ultrasoundincreased significantly membrane flux, and resulted in the recovery of membrane flux.
Keywords/Search Tags:Adsorption, Ultrafiltration, Chitosan, Lead ion
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