Preparation Of Zirconium Hydroxide-Polysulfone Composite And Its Adsorption Properties For SO₄^2- In Brine

Sulphate ions, as an impurity existing in brine and crude salt, can bring a lot ofharmfulness to the salt manufacturing and salt chemical industry. There are manymethods for SO₄^2-removal, in which zirconium hydroxide adsorption method hasoutstanding advantages. Zirconium hydroxide is nontoxic, harmless and easy toadsorb and desorb, but it exists in the form of hyperfine or nano powder, which bringsmany problems in the adsorption and regeneration process. To overcome theseproblems, it is imperative to develop a zirconium hydroxide/polymer compositeadsorbent with suitable dimension for solid separation from the brine.In this paper，the spherical polysulfone particles were first prepared using thephase transformation method, and then zirconium hydroxide was precipitated into thepolymer particles by the inverse titration precipitation method. By employing SEM,HRTEM, IR and XRD techniques, the zirconium hydroxide/polymer compositeobtained had been characterized. The influence on the adsorption ability from themass fraction of polysulfone and precipitation pH value was investigated, and also astatic experiment was proceeded to find out the optimal preparation conditions. Theoptimal preparation conditions determined were as follows: the polysulfonepercentage is10.0%and the precipitation pH value is11.0.The static adsorption experiment was carried out to investigate the affects ofexternal factors to the adsorption ability and the adsorption kinetics. The resultsindicated that the solution pH value has a great influence on the adsorption ability, thesaturated adsorption amount increases with the pH value decreases; the influence ofthe concentration of SO₄^2-display the same rule as the pH value, and as theconcentration reaches to some certain value, the saturated adsorption amount keepsinvariant; the rule is in the contrary to the influence of pH when it comes to the Cl-concentration, but the influence is slight; the saturated adsorption amount augmentswith the temperature rise, while the increase amplitude is little; the Langmuir equationcan meet the isothermal adsorption process, which indicates that it is monolayeradsorption; pseudo second-order kinetic equation can well describe the adsorptionprocess and the diffusion process is the rate-determining step.Dynamic adsorption process was studied in the way of fixed-bed operation, andthe experiment data were fitted by three dynamic adsorption models, the results showthat the breakthrough curves are influenced by polysulfone mass fraction of the composite, the pH value of entering solution, the initial SO₄^2-concentration, the flowrate and the composite adsorbent packing height. It has an offset to lower right orhigher left in different degree, when these factors have a change. Bohart-Adamsmodel can describe the dynamic adsorption process and can predict the breakthroughcurves when the SO₄^2-concentration of entering solution or the flow rate gets achange.Desorption experiment was proceeded utilizing NaOH solution. It was found thatNaOH concentration has little influence on desorption rate, but the desorption goesmore thoroughly under higher NaOH concentration; the saturated adsorption amounthas no significant decline as the adsorption times increase, which shows that thecomposite has good durability.