| Humic acid (HA) is a typical organic matter in surface water body. In chlorinedisinfection process, the HA from could react with chlorine, and generates multipledisinfection byproducts (DBPs) which are harmful to human body. HA are the mainprecursors of chlorine disinfection byproducts, which seriously threaten the safety ofdrinking water. The traditional drinking water treatment processes are almost noremoval efficiency for humic acids, such as coagulation, sedimentation, filtration anddisinfection. Therefore, removing HA from source water has become a fundamentalway to solve the DBPs.Based on the characterization of the HA and magnetic ion exchange resin(MIEX), HA adsorbed on the MIEX resin are investigated in this study by usingstatic adsorption methods. This paper systematically studies the adsorptioncharacteristics and removal mechanism of HA adsorption on the MIEX resin,through the independent variable experiments, the orthogonal experiments, theresponse surface experiments, the isotherm adsorption equilibrium experiments, thekinetics experiments and thermodynamic test.The independent variable experiments shows that the adsorption quantities of HAincrease with the increase of the initial HA concentration, the increase of MIEX resindosage can prompt the removal of HA, HA can be fully mixed with the MIEX resinat150r min-1of agitation speed, When pH value is more than10or less than4, HAcan be removed effectively by MIEX resin，and the increase of temperature isfavorable to the HA adsorption on MIEX resin, uptake of HA on MIEX resin alsoincreases with an increase in ionic strength. The coexistent anions such as PO43-, Cl-,CO32-, BrO3-and Br-could promote and the he adsorption of HA on MIEX resin,while HCO3-and SO42-could inhibit the removal of HA. And the coexistent cationssuch as Ca2+, NH4+, Na+and Mg2+both have different levels of promoting effect on the removal of HA. Also the existence of heavy metal ions such as Cu2+, Pb2+andZn2+can promote the removal of HA onto MIEX resin to some certain extent, whilethe Cr6+and Mn2+are adverse to the adsorption of HA on MIEX resin.The orthogonal experiments show the impact degree of six factors influencingthe removal of HA is in the order of MIEX resin dosage>initial pH ofsolution>(initial solution pH×adsorption time)>(resin dosage×adsorptiontime)>adsorption time>(resin dosage×initial solution pH). The optimum processparameter for HA adsorption is found to be1.0mL L-1,2and40min respectively, forMIEX resin dosage, pH and adsorption time.The second-order polynomial equation of HA removal which has good accuracyand high reliability was established according to the result of response surface test.This equation can efficiently predict the removal of HA on MIEX resin. Interactionanalysis among above factors shows the interaction of MIEX resin dosage and pHvalue, adsorption time and pH value, as well as MIEX resin dosage and adsorptiontime have not significant effect on the removal of HA.0.1mol L-1NaCl solution canregenerate the MIEX resin saturated by HA completely within10min. And the HAcan be still removed effectively by MIEX resin after multipleadsorption-regeneration cycle.The result of adsorption kinetics experiments demonstrates that the pseudosecond-order kinetic model and the Elovich model can be well used to describe theadsorption kinetics process of HA on MIEX resin. Film diffusion is the main ratelimiting step. Chemisorptions is the main control factors of HA adsorption ontoMIEX resin. The fractal research result shows that the adsorption of HA on MIEXresin is nonlinear adsorption.Adsorption equilibrium and thermodynamic study indicates that both Freundlichand Sips isotherm model can be well used to describe the adsorption equilibriumdiscipline of HA on MIEX resin for temperatures ranging from283to313K. Thecalculation results of Freundlich fractal model suggest MIEX resin actually is not2Dhomogeneous surface, and the structure of MIEX resin is complicated. The adsorption of HA on MIEX resin is a thermodynamically spontaneous andendothermic reaction in nature.The result of characterization analysis suggests that MIEX resins embodybenzene ring as the skeleton, including acrylic ester, ethyl benzene, quaternary amine,methyl group, methylene and other functional groups, HA can be well removedwhen the molecular weight is less than300Da, and the three-dimensionalfluorescence intensity of HA significantly reduce after adsorption by MIEX resin.Adsorption of HA on the MIEX resin is multi-molecular layer adsorption, and thepore number and size of MIEX resin decreases to some extent after adsorption. Thecharge attraction, hydrogen bond and-action could make a contribution to theremoval of HA except ion exchange. |
PDF Full Text Request