Study On Scale Inhibition Of Carboxyl And Sulfuric Acid-based Scale Inhibitors In Water Fountain System

In this paper,a green and efficient scale inhibitor was designed and synthesized for the scaling problem of fountain waterscape pools and circulation pipelines.The scale inhibitor effect of calcium carbonate on the homopolymer and blend of scale inhibitor and its monomers was compared.The effects of scale inhibitors and homopolymers and scale inhibitors in different solution p H and concentration of scale inhibitors on the crystal form and morphology of calcium carbonate were analyzed,and the scale inhibition mechanism was analyzed.Furthermore,the scale inhibition effect of the water quality of the simulated fountain water body and the actual fountain water sample was further evaluated.Using 2-acrylamide-2-methylpropanesulfonic acid（AMPS）,allylsulfonic acid（SAS）,and itaconic acid（IA）as monomers,copolymers SAS/AMPS/IA,homopolymers PAMPS,PSAS,PIA,and the three homopolymers are physically mixed to obtain PASA/PAMPS/PIA.The orthogonal experiment method found that the ratio of monomer dosage n（SAS）:n（AMPS）:n（IA）=3:2:4,tert-butanol and APS respectively accounted for 8%and 7%of the total mass,and the reaction temperature was 80℃,reaction time 2h.After the reaction,the water bath was kept at 80℃for2h.The scale inhibition rate of calcium carbonate was 96.23%,and the effect was the best.Gel chromatography and infrared spectroscopy results showed that:SAS/AMP/IA number average molecular weight Mn=1 832,weight average molecular weight Mw=2 216.There are carboxyl group,sulfonic acid group and amide group on the molecular chain,which are the target polymer copolymers.The results of static scale inhibition experiments of different monomer ratios SAS/AMPS/IA and homopolymers PAMPS,PSAS,PIA and blends PASA/PAMPS/PIA:The effect of monomers on the scale inhibition rate in SAS/AMPS/IA is Sort from large to small:IA>AMPS>SAS;when the polymer concentration is 8mg/L,the scale inhibition rate is from large to small:SAS/AMPS/IA>PIA>PAMPS>PSAS;under the same conditions,SAS/AMPS/The scale inhibition effect of IA is better than PASA/PAMPS/PIA.This shows that SAS/AMPS/IA plays a major role in scale inhibition based on the synergistic effect of multiple functional groups on a single molecular chain.Within a certain range,the more carboxyl content on the molecular chain,the better the scale inhibition effect.XRD and SEM results of scale samples after adding SAS/AMPS/IA,PAMPS,PSAS,and PIA showed that:cracks appeared on the surface of Ca CO₃crystals added with PSAS and PAMPS;characteristic peaks of calcite crystal planes（006）and（018）added with PIA The intensity decreases and the surface cracks increase.After adding SAS/AMPS/IA,new characteristic peaks appear on the XRD,the lattice distortion of the Ca CO₃unit cell occurs,and the crystal form changes from calcite to vaterite.Adding SAS/AMPS/IA made the Zeta potential of Ca CO₃crystal surface negative.This is because the carboxyl group on SAS/AMPS/IA is adsorbed on the active growth point of Ca CO₃,which hinders the crystal growth.The non-adsorbed sulfonic acid group increases the negative charge of the chelate surface.It is difficult for the small crystals to collide with each other and become large by electrostatic repulsion Crystal.The presence of steric hindrance in the SAS/AMPS/IA branch chain also prevents the crystals from condensing and growing.Under the same conditions,the scale inhibition effect of the three scale inhibitors is from large to small:PHPMA>SAS/AMPS/IA>PASP.PHPMA contains a phosphonic acid group that has a strong adsorption effect on calcium ions,making it the best antiscalant effect.XRD and SEM results of different copolymer concentrations show that as the amount of SAS/AMPS/IA is increased,the intensity of calcite’s characteristic peaks weakens,and the crystal damage becomes more obvious.When the concentration was 8 mg/L,the Ca CO₃crystals were flat spherical and the surface had many pores.The concentration of SAS/AMPS/IA affects the adsorption and dispersion of Ca CO₃crystals by carboxyl and sulfonic acid groups on the molecular chain.The optimal dosage is to satisfy the equilibrium of SAS/AMPS/IA and Ca²⁺adsorption.XRD and SEM results of different solution p H showed that when the solution p H was 6 and 9,there were some cracks on the crystal surface after adding SAS/AMPS/IA,and Ca CO₃was still in the form of calcite.At p H=8,the surface of Ca CO₃was severely damaged and loose and porous,and the crystal form became vaterite.At low p H,the ability of SAS/AMPS/IA to curl and adsorb crystals is weakened.Too high p H makes the SAS/AMPS/IA acidic structure disappear and the chelation of Ca CO₃is reduced.The water hardness and alkalinity of fountain water were determined by chemical titration.Comparing the results of different regions,seasons,and weather conditions,the results showed that the water hardness was relatively large in summer and sunny days,and the alkalinity decreased during the rainy season.Great influence.The static scale inhibition experiment was performed on the simulated fountain water:the calcium ion concentration was 3mmol/L,the SAS/AMPS/IA scale inhibition rate was 96.1%,and the copolymer water resistance to Ca²⁺concentration of 15mmol/L was 53.1%;The effect of the alkalinity of the water body on the scale inhibition experiment is relatively small;In the laboratory,the fountain water was concentrated 5times,and the scale inhibition rate of SAS/AMPS/IA was only 58.3%.From the SEM results of SAS/AMPS/IA calcium carbonate added to the actual campus fountain water sample,the aggregation degree of Ca CO₃grains became smaller and the scale was loose.SAS/AMPS/IA has a good scale inhibition effect on medium and low hardness and alkalinity water,can hinder the crystal growth process in water,and calcium carbonate cannot condense and precipitate in water.