Study And Application Of Surface Modified Slag-Based Geopolymer Microspheres Adsorbents

Heavy metal pollution from wastewater is a global environmental problems,making a serious threat to human life and health which can be solved by adsorption,one of the most effective methods of heavy metal pollution currently.Geopolymer adsorbent,a new type of green adsorption material which is economic,environmental protection and renewable,can effectively remove a variety of heavy metal ions in waste water.But as an inorganic materials,it's limited in narrow applicable range and single adsorption mechanism of ion exchange in comparison to organic macromo-lecular adsorbent.There have been many researches in the organic modification of common inorganic adsorbent and natural polymer adsorbent,but few studies on geopolymer adsorbent modification.In order to overcome the limitation of geopolymer adsorbent and improve its adsorption performance,a high-efficient heavy metal ion chelator,dithiocarbamate(DTCs),was used to modify it.The main content and results of the study are as follows:(1)Geopolymer/dithiocarbamate compounds(DTC/SGS)synthesized by slag-based geoplymer microspheres(SGS),ethylene diamine(EDA)and carbon disulfide(CS2).The modified optimal formula determined by adding different doses of SGS,ethylene diamine and carbon disulfide,and found that the adsorption amount and removal rate of Cd2+ increased with ethylene diamine and carbon disulfide dosage increased,and increased first then decreased with the SGS dose increased.SGS/DTC composite was characterized by SEM,XRD,FTIR,specific surface area and pore diameter distribution instrument,which proved that dithioamino modification was successfully carried out.(2)By investigating the quality of time,initial concentration,adsorbent dosage and p H,the SGS/DTC complex adsorption capacity of Cd2+ and Pb2+ are studied,the results showed that when the concentration of heavy metal solution less than 200 mg/L,the removal rate of Cd2+ and Pb2+ more than 99%.The maximum adsorption amount of Cd2+ and Pb2+ are 211.2 mg/g and 375.99 mg/g respectively,and adsorption fitted with pseudo-second order dynamic model.(3)With polyethylene amine,carbon disulfide and sodium hydroxide as raw materials to synthesize sodium dithiocarbamate polymer(MDTC),then the dithiocarbamate function groups were grafted to the surface of SGS by chemical grafting method to synthesize dithiocarbamate functionalized geopolymer microspheres(SGS-MDTC).The adsorbent characterized by SEM,FTIR,specific surface area and pore size distribution apparatus,proved successful dithiocarbamate function groups grafting;(4)In batch adsorption experiment,effect of time,initial concentration,adsorbent dosage and p H were investigated.The results show that the maximum adsorption amount of Cd2+ onto SGS-MDTC is 155.2 mg/g,and adsorption process in line with the pseudo-second order dynamics model and D-R model,explain the process of adsorption is mainly chemical adsorption,and conforms to the cavernous adsorption rather than layer-to-layer.(5)In fixed-bed column adsorption experiment,effect of inflow rate,length of fixed-bed and initial concentration on fixed-bed capacity were investigated.The results show that the higher the velocity,the shorter the penetration time;the higher the time and fixed bed length,the longer the breakthrough time;the initial concentration was increased and the breakthrough time was shortened.When the flow rate was 1 m L/min,the column height was 1.5 cm and the initial concentration was 200 mg/L,the adsorption capacity of Cd2+ reached the maximum value of 122.70 mg/g.