Study On The Adsorption Of Heavy Metal Ions From Water By Carboxylated Bentonite

At present,a large amount of Cu²⁺,Pb²⁺and Zn²⁺will be produced in the production process of lead and zinc industry.Only through flocculation,precipitation methods,due to the solubility of the limited product,the treated wastewater is still difficult to meet the relevant requirements.Therefore,an advanced treatment technology is needed to ensure that the relevant emission standards are met.This paper attempts to use a more green environmental protection,high efficiency removal technology for effective removal.Greeted by adsorption,and natural mineral is a kind of range,green energy-saving new adsorbent,the bentonite resources are rich in our country,have certain adsorption ability of common heavy metal ions,so this topic selection accounted for 80%of the total quantity of bentonite in China the calcium base bentonite as raw material,through chemical modification,introducing carboxyl functional groups,In order to enhance its adsorption capacity of common heavy metal ions in water.In this study,dopamine-modified bentonite(DP)was synthesized by dopamine self-polymerization,and the optimal ratio of dopamine to natural bentonite was determined to be5:100.On this basis,carboxylated bentonite(DPS)was obtained by chemical modification.XPS(X-ray photoelectron spectroscopy),XRD(X-ray diffraction),SEM(scanning electron microscopy),FTIR(infrared spectroscopy)and Zeta potential were used to characterize the DPS.The characterization results showed that,after chemical modification,carboxyl functional groups were successfully introduced on the surface of DPS.The optimal pH values for Cu²⁺,Pb²⁺and Zn²⁺adsorption by DPS were 5.5,4 and 4,respectively.The saturated adsorption capacities of Cu²⁺,Pb²⁺and Zn²⁺were 84.35mg/g,232.75mg/g and80.23mg/g.The adsorption kinetics and adsorption model under a single state were investigated.It was found that the adsorption of Cu²⁺and Pb²⁺by DPS accorded with Langmuir adsorption model,and that the adsorption of Zn²⁺accorded with Freundlich adsorption model.According to the model,the maximum adsorption capacities of Cu²⁺,Pb²⁺and Zn²⁺by DPS are 87.26mg/g,241.545 mg/g and 80.23mg/g.The adsorption kinetics shows that the adsorption capacities of Cu²⁺,Pb²⁺and Zn²⁺by DPS are closer to the pseudo-second-order kinetics.The adsorption effect of DPS on mixed ions was explored.By optimizing the experimental conditions,the optimal adsorption pH of the three ions in the mixed state was5.5,and the adsorption capacity of DPS on the three ions in the mixed state was Pb²⁺>.Cu²⁺>Zn²⁺can reach adsorption saturation in about 160 min,and the optimal dosage is 1g/L.The competitive adsorption was investigated.The experimental results showed that the saturated adsorption capacity of Cu²⁺was 51.17mg/g.The saturated adsorption capacity of Pb²⁺was105mg/g.The saturated adsorption capacity of Zn²⁺was 21.5mg/g.Adsorption model experiments show that Cu²⁺and Pb²⁺conform to Langmuir adsorption model,and Zn²⁺conform to Freundlich adsorption model.Both Cu²⁺and Pb²⁺adsorption are homogeneous monolayer on the surface,and the maximum adsorption capacity of Cu²⁺and Pb²⁺reaches53.994 mg/g and 122.1 mg/g,respectively.DPS was applied to the treatment of simulated wastewater,and the residual heavy metal ions in the wastewater and the pH of the wastewater finally met the relevant discharge standards.Considering that DPS has the properties of repeated use and recycling,the cost of DPS treatment should be similar to the traditional process,but the effect is obvious,and it has a certain practical application value,which is in line with the current concept of green production development.