Preparation Of Composite Modified Sepiolite And Their Adsorption Properties For Pb²⁺

In recent years,the balance between economic growth and environmental health has been broken,and the environmental quality of water,atmosphere and soil has continued to deteriorate.The phenomenon of heavy metal pollution in the water body frequently occurs,which seriously affects the development of the ecological civilization and the health of the human body,and does not accord with the sustainable development strategy plan.Lead is a toxic metal,usually identified as a highly toxic element due to environmental accumulation and high mobility Lead in the water generally comes from electroplating,lead-acid batteries,printing and other enterprises discharge industrial waste water.There are many technologies for the treatment of lead-containing wastewater,such as chemical precipitation,ion exchange,membrane separation and so on.However,there are still some problems in these methods,such as secondary pollution,high input cost,complex process and so on.The adsorption method is distinguished from the characteristics of simple operation,low cost and repeated utilization of the adsorbent..Sepiolite is a kind of clay mineral with low price,abundant reserves,special microfiber structure,high specific surface area and ion exchange capacity,active adsorption center and mechanical stability.However,the purity of natural sepiolite is relatively low and the actual specific surface area is small,which affects the adsorption performance.At the same time,sepiolite has strong water absorption and its powder state is difficult to be separated from solid-liquid,which limits the application of sepiolite as adsorbent.Therefore,it is necessary to modify it by some physical and chemical means.If the cheap sepiolite is loaded by the magnetic ferroferric oxide,then the surface modification is carried out on the magnetic ferroferric oxide,so that the multifunctional composite modified sepiolite is obtained,and the problem of the lead pollution of the heavy metal in the water body is effectively solved.In this paper,two kinds of adsorbents with low cost,easy preparation and good adsorption efficiency were introduced.The findings are as follows:1.Natural sepiolite was magnetized by coprecipitation method with natural sepiolite?SEP?as raw material,and then modified with L-Arg?L-Arg?/sodium dodecyl benzene sulfonates?SDBS?as surfactant.Composite modified sepiolite?L-Arg-MSEP/SDBS-MSEP?was prepared.The effect of total iron concentration,L-Arg/SDBS addition amount and reaction temperature on its adsorption performance was investigated by single factor experiment,and the preparation conditions were further optimized by the response surface method.The experimental results show that the optimum preparation conditions of L-Arg-MSEP are:the total iron concentration is 0.28 mg·L^-1,The ratio of L-Arg content to total iron content is 1.10,and the reaction temperature is 84.22?.The optimum preparation conditions for SDBS-MSEP are:the total iron concentration is 0.28 mg·L^-1,the increase of SDBS is 1.17 CEC,and the reaction temperature is 69.15?.2.The structure and properties of sepiolite before and after modification were analyzed by means of infrared spectrum?FT-IR?,scanning electron microscope?SEM?,vibrating sample magnetometer?VSM?,x-ray diffraction?XRD?and specific surface and pore structure analyzer?BET?etc.The results show that the two composite modified sepiolite have magnetic properties with saturation susceptibility of 15.53 emu·g^-11 and 14.26emu·g^-1,respectively.The composite modified sepiolite has no change in the basic structure of sepiolite and has been successfully modified by L-Arg and SDBS.The surface of L-Arg-MSEP is rough and many Fe₃O₄ particles are attached on the surface of the fiber bundle.The linear compact structure of SDBS-MSEP is broken and the surface of sepiolite is covered with a layer of sodium dodecyl benzene sulfonate.The specific surface area of L-Arg-MSEP increased slightly from 32.87 m²·g^-11 to 40.46 m²·g^-1,and the average pore size increased from 3.79 nm to 2.92 nm;The specific surface area of SDBS-MSEP decreased slightly,from 32.87m²·g^-11 to 16.84 m²·g^-1,but the average pore size increased from the original 3.79nm to 5.75 nm.These results indicate that the composite modification can effectively improve the adsorption performance of sepiolite.3.When the initial concentration of Pb²⁺is 200 mg·L^-1,the initial pH=5.0,adsorption time is 2 h and the temperature is 30? and the adsorption dosage of L-Arg-MSEP?SDBS-MSEP and SEP is 2 g·L^-1,6 g·L^-1and 2 g·L^-1,respectively.the removal rates were99.95%,92.82%and 64.35%,respectively.the adsorption capacity was 104.84 mg?g^-1.,97.35 mg?g^-1.,and 67.5mg?g^-1,respectively.The results show that the adsorption capacity of composite modified sepiolite L-Arg-MSEP/SDBS-MSEP)to Pb²⁺is much higher than that of natural sepiolite?SEP?.The adsorption capacity of the three adsorbents is as follows:L-Arg-MSEP?SDBS-MSEP?SEP.4.The adsorption process of L-Arg-MSEP?SDBS-MSEP and SEP to Pb²⁺is the best to fit the quasi-two-order kinetic equation,and the chemisorption is dominant;the langmuir isothermal adsorption model is more in line with the adsorption process of three materials to Pb²⁺,and the adsorption of L-Arg-MSEP?SDBS-MSEPand SEP to Pb²⁺is the single-molecular-layer adsorption;the adsorption process of the sepiolite before and after the composite modification is an exothermic reaction,and the order of the degree of spontaneity:SDBS-MSEP>L-Arg-MSEP>SEP.5.The adsorption process of SDBS-MSEP/L-Arg-MSEP on Pb²⁺is the result of the comprehensive action of chemical adsorption and physical adsorption.