Study On The Treatment Of Compound Heavy Metals Pollution In Source Water Via Adsorption By Nano Illite/smectite Clay

In recent years,heavy metal pollution accidents in water environment occured frequently,and the conventional water supply process are difficult to effectively remove trace heavy metals in water.Adsorption is an effective means to remove heavy metals at low concentration in water.Clay minerals are widely distributed,inexpensive and environmentally friendly,they were often used to adsorb heavy metal ions in water.Illite/Smectite(I/S)clay as a transition type of minerals,which smectite under the diagenesis transforms to illite,is one of typical layered silicate minerals.At present,there is little research on I/S clay as an environmental remediation material,and the report about study of heavy metal pollution in drinking water with low concentration and high flow by clay minerals is less at present.Because nonferrous metals have the characteristics of polymetallic symbiosis,there are no effective measures to deal with the pollution of associated heavy metals caused by the sudden heavy metal pollution.The purpose of this paper is to understand the properties of adsorption of low concentration heavy metals in water by nano I/S clay,in order to explore the effective method to deal with sudden heavy metal pollution.The results were as follows:1.The nano I/S clay appeared a thin layer structure with surface area,average pore diameter,total pore volume and cation exchange capacity were 46.44 m2/g,6.951 nm,0.1091 cm3/g and 24.65 mmol/100g,the potential exchangeable cations K+ is 1.5%.And it's safe for environmental remediation with the content of heavy metals lower than the first level standard of'Environmental Quality Standard for Soils.2.The FT-IR results showed a weak absorption peak in the presence of montmorillonite at 3650 cm-1,by comparison,the mixed layer ratio of the nano I/S clay is about S%=20.The composition of illite and kaolin in the nano I/S clay is found in the XRD pattern.3.The nano I/S clay as an adsorbent was used to adsorb Cd and T1 in micro-polluted water,it's adsorption properties of Cd and T1 was investigated.The effects of clay content,adsorption time,solution pH,adsorption temperature and concentration of Cd and T1 on the adsorption performance of Cd and T1 onto nano I/S clay were studied.In addition,the isotherm,thermodynamics and dynamics for the adsorption were analyzed.The results showed that,the good adsorption performance of nano I/S clay to Cd and T1 overcame the complex operation steps and excessive use of agentia by chemical method in the removal of trace T1,the solution with 0.1 mg/L Cd and 0.002 mg/L T1 can reach'Environmental Quality Standards For Surface Water' when pH was neural and 7.5 g/L nano I/S clay dosage at room temperature,the reaction reached equilibrium in 15 min.Moreover,the solution with 0.20 mg/L Cd and 0.004 mg/L T1 can reach the standard when 10.0 g/L nano I/S clay dosage added.The adsorption course with nano I/S clay had high degree to fit pseudo-second order kinetic equation.The Langmuir model presented better a fit for the adsorption equilibrium,it revealed the surface of nano I/S clay is homogeneous,and its adsorption to Cd and T1 were monolayer.Meanwhile,the thermodynamic parameters revealed that the adsorption process was a physical process with the increasing of entropy.Therefore,the adsorption of Cd and T1 onto nano I/S clay is the result of chemical adsorption and physical adsorption.4.The effects of solution pH,adsorption time and clay content on the removal of Cd,Sb,As and T1 in compound micro-polluted water were studied by adsorption orthogonal experiment with nano I/S clay.The combined treatment process of adsorption-coagulation was used to investigate the treatment effect of compound micro-polluted water under different conditions.The results of orthogonal experiment showed that the order of effective extent was adsorbent dosage>adsorption time>solution pH.The results of combined treatment process showed that after the adsorption,the supernatant was added with 30 mg/L PFS,the removal rate of Cd,Sb,As and T1 was 88.9%,87.0%,65.8%and 86.3%respectively when the amount of nano I/S clay was 2.5 g/L.