Adsorption Properties Of Heavy Metals And Dyes In Aqueous On Potato Residue

With the progress of society and economic development,the rapid development of industry has also brought a lot of environmental problems.For example,a large amount of wastewater containing heavy metal ions and dyes is discharged into natural water bodies without treatment or partial treatment.These two types of pollutants have the characteristics of strong toxicity,difficult degradation and easy enrichment.If not dealt with in time,it will not only have a bad impact on the environment,but also enrich through the food chain,endangering the health of organisms and humans.Therefore,the effective treatment of wastewater containing heavy metal ions and dyes is an urgent problem to be solved by researchers and engineering technicians.Among the existing treatment methods,the adsorption method has received extensive attention and research due to its advantages such as high adsorption efficiency,low cost,and simple equipment.In this paper,potato residues from agricultural and forestry wastes are used as raw materials,which are activated and modified to coat chemically stable quartz sand to prepare heavy metal ions and dye adsorbents（QS@PR）.Through the static adsorption experiment and the dynamic adsorption experiment（fixed bed）,the adsorption method and adsorption performance of the adsorbent for Cd²⁺,Cu²⁺and MB were explored.The details are as follows:（1）According to the scanning electron microscope（SEM）results,the potato residue after activation is rougher in surface,more porous and porous in texture than the potato residue before activation,and its surface structure is more conducive to adsorption.The activated potato residue was successfully coated on the surface of quartz sand through the adhesive properties of waterborne polyurethane.The results of X-ray diffraction（XRD）and thermogravimetric analysis（TGA）indicate that the potato residues have active components that adsorb heavy metal ions and dyes.According to the results of infrared spectroscopy（FTIR）analysis,compared with the potato residue before activation,the potato residue after activation has a larger number of active functional groups,and the active adsorption sites increase,which is more conducive to the adsorption.（2）In the static adsorption experiment,the effects of adsorbent dosage,p H,initial pollutant concentration,adsorption time and temperature on adsorption were studied,and the adsorption kinetics,adsorption isotherms and adsorption thermodynamics were fitted.Analysis to explore the adsorption characteristics and adsorption capacity of the adsorbent.Finally,the desorption regeneration performance of the adsorbent was investigated.Static adsorption results show that the optimal pH for QS@PR adsorption of Cd²⁺,Cu²⁺and MB is 5,5 and 8 respectively;as the amount of adsorbent added increases,the removal rate of Cd²⁺,Cu²⁺and MB also gradually increases,considering the economy Factors,the optimal dosage of adsorbent is 10 g,10 g and7.5 g respectively;with the increase of the initial concentration of pollutants,the adsorption capacity of the adsorbent gradually increases,indicating that the active adsorption sites on the surface of the adsorbent are gradually occupied;The adsorption rate of Cd²⁺,Cu²⁺and MB by QS@PR is fast,and the adsorption equilibrium state is basically reached within 10 minutes,and the removal rate is high;as the temperature increases,the adsorption amount of Cd²⁺and MB by QS@PR decreases,and the temperature reduction is beneficial to QS@PR Adsorption of Cd²⁺and MB.It can be known from the fitting results of the adsorption kinetic model that the adsorption process has a high degree of fitting with the quasi-second-order kinetic model,and the correlation coefficient（R²）is greater than 0.99,indicating that the adsorption rate is mainly controlled by chemisorption;The degree of fitting between the adsorption isotherm and the Langmuir adsorption isotherm equation is higher than that of the Freundlich adsorption isotherm equation,indicating that the adsorption is a monolayer adsorption process;from the adsorption thermodynamic fitting results,it can be seen that the enthalpy change when QS@PR adsorbs Cd²⁺and MBΔH⁰<0,Indicating that the adsorption of Cd²⁺and MB is an exothermic reaction;the entropy changes during the adsorption processΔS⁰<0,indicating that when QS@PR adsorbs Cd²⁺and MB,the degree of disorder of the wastewater solution system is reduced and the order is improved;ΔG⁰<0,It shows that the adsorption process of Cd²⁺and MB by QS@PR is spontaneous.Competitive adsorption experiments of heavy metal ions with Na⁺and Ca²⁺in aqueous solution showed that the increase in Na⁺concentration had little effect on the adsorption of Cd²⁺and Cu²⁺,and the increase in Ca²⁺concentration had no effect on the adsorption of Cu²⁺,but had a greater effect on the adsorption of Cd²⁺.The desorption regeneration experiment shows that 0.1mol/L HNO₃ solution can desorb QS@PR after adsorption of Cd²⁺,Cu²⁺and MB.Through three rounds of desorption experiments,the adsorption capacity has decreased and the regeneration performance needs to be improved.（3）In the dynamic adsorption experiment（fixed bed）,the effects of flow rate,initial concentration of pollutants and fixed bed depth on adsorption were studied,and the experimental data were fitted by the Adams-Bohart,Thomas,and Yoon-Nelson models.The adsorption effect of QS@PR on the binary pollutant system was explored.Finally,the desorption performance of QS@PR in a fixed bed was tested.Dynamic adsorption experiments show that the faster the flow rate,the higher the initial concentration of pollutants and the lower the depth of the fixed adsorption bed,the steeper the penetration curve,the shorter the time to reach adsorption equilibrium,the smaller the breakthrough time of the fixed adsorption bed The amount of adsorption has also decreased.In the Cd-Cu binary solution system,the affinity of Cu²⁺in the aqueous solution is greater than that of Cd²⁺,and the adsorbed Cd²⁺is desorbed from the adsorbent,resulting in the Cd²⁺effluent concentration exceeding the influent concentration at the peak;in Cd-MB and Cu-Compared with the single pollutant in MB binary system,the penetration time is reduced,indicating that Cd²⁺and MB and Cu²⁺and MB mutually inhibit each other.The results of the continuous desorption regeneration experiment show that QS@PR can desorb the adsorbent with 0.1mol/L nitric acid solution after saturating the adsorption of Cd²⁺,Cu²⁺and MB,and the desorption is basically completed within 30min.The desorption speed is fast,but the adsorption capacity is Therefore,the desorption regeneration performance of the adsorbent needs to be improved.The fixed adsorption bed data is fitted by Adams-Bohart,Thomas and Yoon-Nelson models,the correlation coefficients are all greater than 0.9,the three models can fit the adsorption process well,but the Adams-Bohart model is only used to describe the penetration The initial part of the curve,and the Thomas and Yoon-Nelson models apply to the entire adsorption process.And under the same research conditions,the correlation coefficients of Adams-Bohart model fitting are slightly lower than those of Thomas and Yoon-Nelson models.Therefore,both Thomas and Yoon-Nelson models can be used to predict the adsorption performance of fixed adsorption beds.Experimental research shows that using potato residue as raw material as an adsorbent not only has the advantages of wide source,low cost and environmental friendliness,but also can effectively treat wastewater containing heavy metal ions and dyes.It provides an effective way for the treatment of waste water containing Cd²⁺,Cu²⁺and MB and the recycling of potato residues,and also achieves the purpose of treating waste with waste.