Removal Of HPAM From Aqueous Solution By Coagulation-adsorption Method

In this paper, the water-soluble magnesium salts were added to alkaline solutions to obtain freshly generated magnesium hydroxide (FGMH). The FGMH particle have a high surface free energy with a small particle size, large adsorptive surface area and a positive surface charge, which can be used to attract HP AM. The particle size of the FGMH and the hydroxide precipitates before and after adsorption were characterized by dynamic light scattering (DLS) and Fourier-transform infrared spectroscopy (FTIR). Batch coagulation-adsorption experiments were conducted to determine the effect of contact time, dosage, pH and temperature. Langmuir and Freundlich isotherms were used to analyze the HPAM adsorption by the FGMH. Moreover, Visual MINTEQ which is an equilibrium speciation model that can be used to calculate the equilibrium composition of dilute aqueous solutions in the laboratory or in natural aqueous systems were used to analyze the disposal mechanism. And the experimental results showed that:(1) Effects of reaction time, dose of the leaching solution and pH were studied. The results showed that the FGMH was rapid and effective in removing the HPAM in water solutions. The removal rate reached maximum at120s. The removal rate increased with increasing amount of MgCl2dosage, and the appropriate MgCl2dosage were3.0g/L when the concentration of the HPAM was100mg/L. And the optimum pH for the FGMH to remove HPAM was12.5. The removal efficiencies were all over90%for different concentration HPAM under the condition.(2) The isotherm data was consistent with both the Freundlich and Langmuir models, and the adsorption of HPAM by FGMH is a favorable adsorption process. The adsorption reaction was exothermic in nature, and that the solution temperature has a significant effect on HPAM adsorption. When the temperature was303K, the saturation adsorption capacity of the HPAM was133.3mg/g, which indicated that FGMH displayed superior adsorption capacities to the HPAM.(3) The FT-IR showed that the HPAM was absorbed by the FGMH. (4) According to the analog computation analysis using Visual MINTEQ, the removal mechanism of HPAM by FGMH is a coagulation-adsorption process involving charge neutralization and surface complexation.