Absorbency And Adsorption Preporties Of Homo-and Co-polymer Superabsorbents Of 2-acrylamido-2-methylpropanesulfonic Salt

The superabsorbents, poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) and poly (2-acrylamido-2-methylpropane sulfonic acid-co-maleic anhydride) P(AMPS/MAH), are prepared by means of water solution polymerization. The absorbency and adsorption characterizations of them are investigated.By combining orthogonal design and single-factor-study, mass percents of monomer, initiator and crosslinker, neutralization degree and reaction temperature are studied, the optimized polymerization conditions are obtained as follows: mass percent of monomer is 35%, mass percents of initiator and crosslinker compared to the amount of monomers are 0.04% and 0.03%, respectively. Neutralization degree is 60%, reaction temperature (time) are 50℃(2h), 60℃(3h) and 70℃(2h). Under these conditions, the absorbency of PAMPS superabsorbent in distilled water and in 0.9%(wt%) NaCl aqueous solution are 4062 and 165g/g, respectively.Through the research of the absorbency for PAMPS and it adsorption of Pb²⁺, Cu²⁺ and Zn²⁺, it is found that the absorbency and adsorption ability of PAMPS are both better; the absorbency and adsorption velocity is relatively fast. And the relationship of absorbency and adsorption with the time can be described by pseudo two order kinetic equations. The adsorption of Pb²⁺, Cu²⁺ and Zn²⁺ onto different PAMPS increases with the increasing of the initial solution concentrations, mass percents of crosslinker and neutralization degree. Moreover, for the effect of the initial solution concentrations, Langmuire isotherm can fit for the experimental data very well. And the adsorption behavior is discussed for PAMPS in the binary and ternary solutions of Pb(NO3)2, Cu(NO3)2 and Zn(NO3)2, the results have shown that there is the higher selectivity for the Pb²⁺ adsorption. The adsorption capacities for Pb²⁺, Cu²⁺ and Zn²⁺ are 155, 29 and 24mg/g in the ternary solutions which the initial solution concentrations is 0.002mol/L. The desorption behavior in 1mol/L HCl solution are also discussed, it is found that the desorption percent increases with the time and the velocity is very fast, it reached the equilibrium about 10 minutes.Furthermore, P(AMPS/MAH) samples of three different mol ratios are prepared, and their absorbency and the adsorption of them for Pb²⁺, Cu²⁺ and Zn²⁺ are investigated. It is found that the absorbency and adsorption ability of P(AMPS/MAH) are both better, the absorbency and adsorption velocity is relatively fast, and the relationship of absorbency and adsorption with the time can be described by pseudo two order kinetic equation, too. The amount of adsorption for Pb²⁺, Cu²⁺ and Zn²⁺ increases with the increasing metal ion concentrations, and it is inferred that AMPS play a primary function for the adsorption of heavy metal ion onto P(AMPS/MA) with different ratios of AMPS and MA. For the effect of the initial solution concentrations, Langmuire isotherm can fit for the experimental data very well, too. The results have shown that there is the higher selectivity for the Pb²⁺ adsorption in the binary and ternary solutions of Pb(NO3)2, Cu(NO3)2 and Zn(NO3)2. The adsorption capacities for Pb²⁺, Cu²⁺ and Zn²⁺ are 186, 38 and 35mg/g, respectively, in the ternary solutions which the initial solution concentrations is 0.002mol/L. The effect of the solution pH is also discussed. It is found that, when the pH chang from 1.7 to 6.8, the adsorption capacity for Pb²⁺, Cu²⁺ and Zn²⁺ increases with increasing of the solution pH and then reached the equilibrium value: 250, 87 and 83mg/g. The pH for the maximal adsorption capacity of Pb²⁺, Cu²⁺ and Zn²⁺ are 5.5, 5.6 and 6.2, respectively. The desorption percent increases with the time in 1mol/L HCl solution, and the velocity is very fast, it reached the equilibrium about 10 minutes, too.