Surface Modification Of Calcium Carbonate By Self-Stabilized Precipitation Polymerization And It’s Adsorption Property

Calcium carbonate（Ca CO₃）has the advantages of abundant resources and low price,and it is a hot topic to use Ca CO₃as a low-cost adsorbent in waste water treatment.However,the commonly used Ca CO₃has poor adsorption performance due to its compact structure and the lack of surface functional groups.In this dissertation,two kinds of anhydride functionalized Ca CO₃core-shell particles were successfully prepared by self-stabilized precipitation polymerization（2SP）with Ca CO₃as core substrate.The high density of anhydride groups in the coating layer were further modified to obtain carboxylate functionalized adsorbent.Taking Cu²⁺and MB as the model pollutants,the adsorption properties and adsorption mechanism of these two adsorbents were investigated systematically.The main contents and achievements are summarized as follow:1.Spherical Ca CO₃（SCC）of vaterite structure was successfully prepared with sodium polystyrene sulfonate as crystal regulator.Using divinylbenzene（DVB）and maleic anhydride（MAH）as comonomers,a cross-linked poly（DVB-co-MAH）（PDM）shell layer which contains a large number of functional anhydride groups was directly constructed on the surface of SCC by the way of 2SP polymerization.The effects of reaction temperature,core-shell ratio,reaction time and other factors on the PDM shell layer were investigated,and the surface modification conditions were optimized.After further hydrolysis of the anhydride groups in the shell layer of SCC@PDM,the carboxylate functionalized SCC@PDM-COO^-was successfully prepared.2.Taking Cu²⁺and MB as model pollutants,the effects of solution p H,adsorbent dosage,initial adsorbate concentration and contact time on the adsorption property of SCC@PDM-COO^-were investigated.The experimental results showed that SCC@PDM-COO^-exhibited excellent adsorption property for Cu²⁺and MB.The adsorption capacity increased remarkably with the increase of solution p H value,and the adsorption behavior conformed to quasi-second-order kinetic model and Langmuir isothermal model.The adsorption of Cu²⁺and MB on SCC@PDM-COO^-was a single-layer adsorption mainly based on electrostatic interaction.The theoretical maximum adsorption capacity of Cu²⁺and MB were 480.2 and433.7 mg/g,respectively.3.PDM coated precipitated calcium carbonate（PCC@PDM）with core-shell structure was successfully obtained by direct 2SP polymerization of DVB and MAH using industrial PCC as the core substrate.The carboxylate functionalized PCC@PDM-COO^-contained high density of carboxyl groups in the shell layer was facilely prepared through hydrolysis of anhydride groups.The stability of the prepared PCC@PDM was greatly improved,and their morphology and crystal structure wouldn’t change under high temperature and alkaline environment,which was conducive to their practical application under complex situation.4.The adsorption property of PCC@PDM-COO^-for Cu²⁺and MB were investigated by changing the solution p H,adsorbent dosage,temperature,initial adsorbate concentration and contact time.The experimental results showed that the adsorption capacity and removal efficiency increased with the increase of solution p H value.Through analyzing the adsorption data,it was found that the quasi-second-order kinetic model and Langmuir isothermal model can better describe the adsorption process of Cu²⁺and MB,the theoretical maximum adsorption capacity of Cu²⁺and MB were 467.3 and421.9 mg/g,respectively.Thermodynamic analysis showed that the adsorption of Cu²⁺and MB was a spontaneous process and temperature rise was beneficial to adsorption.