Preparation And Properties Of Heavy Metal Ion Adsorbing Materials In Water

Water is required for the maintenance of all life forms.Due to accelerated industrial activities and technological development,there has been an increase in the release of these heavy metals into the environment,thus posing a significant threat to the environment and public health.Heavy metals are toxic,non-degradable,and can be bioaccumulated through food chain,besides,degradation is very slow under natural conditions,so it is urgent to find ways treat wastewater polluted by heavy metal.Most recently,adsorption has become one of the most promising technologies over other traditional treatments for the treatment of wastewater containing heavy-metal ions,it produces non-toxic by-products;also has low initial cost and it is rather simple in terms of design and operation of the treatment unit.Nevertheless,adsorbent is the body of adsorption treatment,so it is urgent to research and develop effective adsorbent to treat heavy metal pollution,especially for various metal ions simultaneously and particularly for As(Ⅲ),which are the topics of this paper.In this work,a magnetic thiolated/quaternized-chitosan composites was designed and prepared to remove various ions from wastewater.Characterization by FTIR,SEM,VSM and TGA confirmed the structure and composition of the adsorbent.The composites showed high efficiency to remove various metal ions(As5+,As3+,Cu2+,Hg2+,Zn2+,Cd2+,Pb2+)simultaneously under pH 7 within 60 min,especially for Pb2+,with a high adsorption capacity of 235.63 mg/g,which was higher than many reports,but worse for As3+,Adsorption isotherm fitted well with Sips model,indicating that the adsorption process contained different types.Adsorption kinetic indicated that the adsorption was promoted by a chemical process,and XPS analysis proved that the adsorption was promoted by the complexation of thiol groups and heavy metal ions.Moreover,the composites showed good regeneration performance,and its adsorption efficiency of Pb2+ was still over 93%even after 5 recycles.The above result showed that arsenic(Ⅲ)was hard to remove,therefore,to improve the adsorption performance of adsorbent for arsenic ion,As(Ⅲ)imprinted magnetic Fe3O4-N-(2-hydroxyl)propyl-3-trimethyl ammonium chitosan chloride(HTCC)composite nanoparticles(As(Ⅲ)-IMHNPs)was prepared via micro-emulsions method and ions imprinted technology with HTCC as functional monomer.The As(Ⅲ)-IMHNPs was efficient and selective to adsorb As(Ⅲ)with the maximum adsorption capacity at 11.52 mg/g which got in 5 mg/L As(Ⅲ)solution.With the imprinting of As(Ⅲ),the selectivity of As(Ⅲ)-IMHNPs was enhanced and the effects of competing ions on As(Ⅲ)removal were greatly reduced.The imprinted factor was 1.02～1.17 under interference of co-exist ions.Moreover,the nanoparticle showed good regeneration performance,and its adsorption efficiency of As(Ⅲ)was still above 75%even after 10 recycles.The adsorption behavior of As(Ⅲ)on As(Ⅲ)-IMHNPs could be better described by pseudo-second-order model,which indicated that the adsorption was promoted by a chemical process.Compared As(Ⅲ)-IMHNPs to NIMHNPs,the imprinted effect of selectivity,was not obvious,therefore,another As(Ⅲ)ion imprinted polymer(As(Ⅲ)-ⅡP)was designed and prepared via emulsion polymerization with cationic monomer 2-methacryloyloxyethyl-trimethyl ammonium chloride(DMC)as functional monomer,ethylene glycol dimethyl acrylate(EGDMA)as cross-liner,and ammonium persulfate and sodium bisulfite as redox initiator.The product was characterized by FTIR,SEM,TEM,XRD and TGA.Batch adsorption experiments were performed to evaluate the adsorption conditions and selectivity.The results showed that the maximum adsorption capacity was 0.38 mg/g,which got in 1 mg/L As(Ⅲ)solution at pH 7,adsorbent dosage 2 g/L and temperature 30 ℃.And the imprinted factor was 2.15-3.36 under interference of co-exist ions,indicating high selectivity of As(Ⅲ)-IIP.Adsorption isotherms fitted well with Sips model,and the adsorption behavior of As(Ⅲ)could be better described by pseudo-second-order model,which indicated that the adsorption was promoted by a chemical process.