Functional Modification Of Rectorite Composites And The Application In Wastewater Treatment

Rectorite is an interstratified silicate mineral composed of dioctahedral mica-like layer and dioctahedral smectite-like layer.The interlayer cations Na+ in rectorite can be easily exchanged with either inorganic or organic cations,so rectorite can absorb cationic metals and dyes.However,raw rectorite exhibits poor removal ability toward anions and neutral organic compounds.With the unique properties of large surface area,adjustable interlayer spacing and exchangeable ability,rectorite has great potential in wastewater treatment after being modified.Firstly,porous rectorite/starch gels(PRSs)were fabricated by hydrogel freezing,solvent exchange and ethanol drying.Two modifications were adopted without destroying the porous structures.Starch components were removed to obtain the calcinated PRSs(CPRSs);and starch components reacted with carbon sulfide to obtain the porous rectorite/starch xanthate composites(PRSXs).The chelation could form between xanthate groups and Pb2+,and improve the adsorption of Pb2+.The maximum adsorption capacity could reach 277.0 and 180.8 mg/g for MB by CPRS and Pb2+ by PRSX,respectively.Secondly,to improve the adsorption ability towards anion by rectorite,magnetic Fe3O4 and cetyl trimethyl ammonium bromide(C TAB)were introduced onto the layers of rectorite to fabricate the rectorite/Fe3O4-CTAB composite(REC/Fe3O4-CTAB).The magnetic iron oxide not only expanded the interlayer spacing of rectorite,allowing more CTAB molecules to enter rectorite layers,but is favorable for separating the adsorbent form aqueous solutions.The maximum adsorption capacity could reach 182.1 mg/g for NO3-and 174.5 mg/g for PO43-.Lastly,in order to improve the removal ability towards neutral organic compound by rectorite,rectorite was first intercalated by acidified chitosan to fabricated ultra-light porous rectorite/chitosan gel(REC/CTS)and gold nanoparticles(AuNPs)were then loaded on the rectorite/chitosan support to fabricate rectorite/chitosan/AuNP catalyst.The rec torite/chitosan/AuNP catalyst showed excellent catalytic efficiency,recyclability and durability.Besides,a reaction column filled with REC/chitosan/AuNP gel was designed and applied to the consecutive catalysis of 4-nitrophenol.More than 95% conversion efficiency of 0.3 mmol/L 4-nitrophenol solution could be achieved when the rate of effusion of the 4-nitrophenol substrate in the reaction column was 3 mL/min.