| Pure terephthalic acid (PTA) is the main material in the polyester industry. There isa large amount of wastewater in the refining unit of PTA. The main components in thewastewater after organic acids are removed via the method of ultrafiltration andreverse osmosis are metal ions like Co(Ⅱ) and Mn(Ⅱ). Co(Ⅱ) and Mn(Ⅱ) arecatalyzer of the production, it is important to recycle these metal ions to protect theenvironment and decrease production costs.In this paper, using ion exchange resin to recover Co(Ⅱ) and Mn(Ⅱ), theadsorption process was studied systematically. Firstly, through the resin selectionexperiments,001×7×7resin showed a better capacity and desorption rate. batchexperiments were performed to study the effects of various parameters, such asstirring speed, temperature, resin dosage and pH on the adsorption process. the resultsindicated, the effect of external diffusion was eliminated at210rpm. The adsorptionprocess of Co(Ⅱ) and Mn(Ⅱ) is endothermic. Increasing the resin dosage increasedthe percent removal of Co(Ⅱ) and Mn(Ⅱ), higer pH favor the process.Secondly, the dynamic adsorption and desorption process of Co(Ⅱ) and Mn(Ⅱ)were studied with the selected001×7×7resin, and the optimized operation conditionswere obtained. When the flow rate was6mL/min and the temperature50℃, theadsorption capacity of Co(Ⅱ) and Mn(Ⅱ) was35.73，38.60mg/g, respectively. Whenthe concentration of H2SO4was1.0mol/L, the flow rate1mL/min and thetemperature30℃,the desorption rate of Co(Ⅱ) and Mn(Ⅱ) was98.99%,95.19%,respectively. Moreover, the resin regenerative experiments indicated that001×7×7resin regeneration had good repetition.Thirdly, the thermodynamics and kinetics behavior of single Co(Ⅱ) and Mn(Ⅱ) by001×7×7resin have been investigated. Equilibrium adsorption data of Co(Ⅱ) andMn(Ⅱ) were fitted to Langmuir adsorption isotherms. The adsorption of Co(Ⅱ) andMn(Ⅱ) on this resin followed pseudo-first-order kinetic model and pseudo-second-order kinetic model, respectively. The apparent activation energy of Co(Ⅱ) andMn(Ⅱ) was20.67,28.35kJ/mol, respectively. The kinetics experiments showed thatthe paticle diffusion was the main rate limiting step.The batch competitive adsorption of Co(Ⅱ) and Mn(Ⅱ) onto the001×7×7resinwas studied. The results showed that the adsorption of Mn(Ⅱ) on the resin was strongger than Co(Ⅱ). The competitive adsorption of Co(Ⅱ) and Mn(Ⅱ) onto theresin both fit the Langmuir competitive model. The competitive adsorption kineticsdata of Co(Ⅱ) and Mn(Ⅱ) both follows pseudo-first-order kinetic model. The particlediffusion of Co(Ⅱ) and Mn(Ⅱ) in this ion exchange resin was shown to be the mainrate limiting step. The dynamic competitive adsorption indicated that the sumequilibrium adsorption capacity of Co(Ⅱ) and Mn(Ⅱ) on the resin was equivalent tothe single equilibrium adsorption capacity of Co(Ⅱ) and Mn(Ⅱ). |
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