Removal Of Heavy Metals From Aqueous Solutions And Paddy Soils By Bouyant DTCS/ALG/HGMs Sorbent

In recent years,the problem of heavy metal pollution in water bodies and soils has become more serious.Heavy metals not only seriously endanger the ecological environment,but also enter the human body through the food chain,thus endangering human health.At present,the adsorption method is widely used to treat heavy metal polluted wastewater,but since ordinary adsorbents are generally difficult to separate from the soil,the application of adsorption to remove heavy metals in the soil is rarely reported in the literature.In view of the above problems,this paper has developed a new type of bouyant biosorbent for the removal of heavy metals in aqueous solution.At the same time,in order to remove heavy metals from the soil,this paper indirectly removes the heavy metals on the soil particles by fully contacting the adsorbent with the mixed solution of soil and water and adsorbing the heavy metals from the soil particles to the solution through the adsorbent adsorption.Purpose,and the adsorbent can be separated from the soil solution after adsorbing heavy metals.The DTPA-modified chitosan（DTCS）and hollow glass microspheres（HGMs）were encapsulated in calcium alginate gel beads using sodium alginate（ALG）encapsulation properties and treated with glutaraldehyde in an acidic solution.The new type of floatable adsorbent DTCS/ALG/HGMs was obtained by cross-linking,and the adsorption and adsorption mechanism of the adsorbent on Cu and Cd in heavy metal contaminated aqueous solution and heavy metal contaminated paddy soil were further studied.The specific research results are as follows:（1）The new floatable adsorbent DTCS/ALG/HGMs was synthesized and prepared,and the composition and structure of the material were characterized by scanning electron microscopy（SEM）,thermogravimetric analyzer（TGA）and Fourier transform infrared spectroscopy（FTIR）.The SEM results showed that the surface of the hollow glass microspheres was coated with a composite polymer film of DTCS and ALG.The TGA results showed that the content of organic polymer in the adsorbent was 35.2%.Various characteristic peaks in FTIR proved HGMs and DTCS in the adsorbent.The presence.（2）The adsorption performance of DTCS/ALG/HGMs on Cu²⁺and Cd²⁺ions in aqueous solution was studied.In aqueous solution,the maximum adsorption capacities of adsorbents for Cu²⁺and Cd²⁺were 33.5mg·g^-1and 48.0 mg·g^-1,respectively.The presence of Na⁺and Ca²⁺in the solution had no significant effect on the adsorption of Cu²⁺and Cd²⁺by the adsorbent.Studies have shown that the adsorption of Cu²⁺and Cd²⁺in water by the adsorbent is combined with a pseudo-second-order kinetic model with a certain degree of intraparticle diffusion.The adsorption isotherm curve indicates that the adsorption of Cu²⁺in the water by the adsorbent conforms to the Sips model,which proves that the adsorption of Cu²⁺in the water by the adsorbent occurs in the mixed adsorption between homogeneous and heterogeneous;the adsorption of Cd²⁺in the water by the adsorbent is in accordance with Freundlich isotherm.The adsorption model indicates that the adsorption of Cd²⁺in water is the adsorption on the heterogeneous surface.（3）The removal performance of DTCS/ALG/HGMs on heavy metals in Cd-contaminated paddy soil,high-concentration Cu-contaminated paddy soil and low-concentration Cu-contaminated paddy soil was investigated.The results showed that5%dose of adsorbent contaminated rice field with Cd.The maximum removal rates of high-concentration and low-concentration Cu-contaminated paddy soils were 34.9%,92.0%and 77.3%,respectively.According to the kinetic data analysis,the adsorption of high-concentration and low-concentration Cu-contaminated soil by the adsorbent combined with the Elovich model and the pseudo-second-order kinetic model respectively proved that the adsorption of Cu by Cu in contaminated soil is a complex and heterogeneous phase.The chemical process.The results of morphological analysis indicated that the adsorbent can effectively remove the exchangeable and carbonate-bound and iron/manganese oxide-bound（reducible）Cu in the soil.