Adsorption Characteristics And Mechanism Of Modified Mangosteen Shell Biochar On Heavy Metal Nickel Ions (Ni(II)) In Water

With the development of modern industry,environmental problems such as shortage of water resources and deterioration of water quality have become more prominent.And the treatment of heavy metal Ni(?)pollution in water bodies has also attracted more and more attention.Nickel often appears in the nickel plating industry,machine manufacturing,and the wastewater of the metal processing industry,chronic over-intake or over-exposure can cause damage to the human body's heart,muscle,brain,lung,liver,kidney and other organs.Biochar is a kind of solid material produced by high temperature pyrolysis of biological residues under hypoxic conditions.It has the features of porous structure,refractory to degradability and adsorb-ability.Since biochar is often prepared from crop wastes,fruit husks and peels,it has a wide range of sources and its cost is low.In recent years,it has attracted much attention in the environmental field.Therefore,in this study,the mangosteen shell in the fruit shell was used as the raw material for preparing biochar.The mangosteen shell biochar was prepared by slow pyrolysis,and then the modified mangosteen shell biochar was prepared by chemical modification.Single factor experiment and response surface experiment were used to optimize the conditions for preparing the best modified mangosteen shell biochar.With the help of specific surface area and SEM analysis,pH measurement,thermal stability analysis,infrared spectrum analysis,element analysis and X-ray photoelectron spectroscopy analysis,comparative analysis of the changes in the surface morphology and surface functional groups of the mangosteen shell biochar before and after modification were carried out.In the study on the adsorption of Ni(?)by modified mangosteen shell charcoal,the dosage,pH,ionic strength and other related factors that affect the effects of modified mangosteen shell charcoal on the adsorption of Ni(?)were changed,To obtain the optimum conditions for removal of Ni(?)from water by mangosteen shell charcoal.Through the adsorption thermodynamics and adsorption kinetics experiments,preliminary exploration of the process of biochar adsorption of nickel,using Fourier infrared spectroscopy analysis,XPS analysis and other analytical methods and measuring the zeta potential of biochar,further explore the improvement The adsorption mechanism of natural mangosteen charcoal on Ni(?).Finally,through the adsorption-desorption cycle experiment,the properties and reusability of the modified mangosteen shell biochar were analyzed.The main results of this paper are as follows:(1)Explore the effects of different modification methods on the modification of mangosteen shell biochar.In the experiment,five modification methods of K₂FeO₄,KOH,ZnCl₂,H₃PO₄and K₂FeO₄+KOH were used to modify the mangosteen shell charcoal,And it was found that the modified mangosteen shell charcoal obtained by the simultaneous modification of KOH and K₂FeO₄has the best adsorption effect for Ni(?).When the pyrolysis temperature is 350?,the potassium ferrate concentration is 0.80%,and the mass ratio of potassium hydroxide to mangosteen husk biochar is 2.5,the adsorption capacity of the modified mangosteen husk biochar to Ni(?)reaches 75.9104 mg/g.The surface of the modified mangosteen charcoal has a porous structure.The specific surface area has increased from 0.0894 m²/g to 13.086 m²/g,the pH has decreased from 10.21 to 8.1,and the zeta potential has decreased from-46.7 to-55.3.The properties of mangosteen shell charcoal have changed,and the content of functional groups such as-OH,CC,C=O,and CO on the surface of biochar has also changed significantly.(2)Explore the adsorption characteristics and mechanism of Ni(?)by modified mangosteen shell biochar.The optimal pH for the modified mangosteen shell charcoal to adsorb Ni(?)is 6,the dosage is 10 mg(v=10 mL),and the adsorption capacity is 75.9104 mg/g;The optimal pH of)is 4 when the unmodified mangosteen shell charcoal adsorbs Ni(?),and the dosage is 10 mg(v=10 mL).At this time,the adsorption capacity is 9.7087 mg/g.After modification the adsorption capacity of the modified bamboo shell charcoal for Ni(?)is significantly increased.The adsorption effect of mangosteen shell charcoal on Ni(?)before and after modification is affected by the ionic strength.Competitive ions Cd(?),Cu(?),Pb(?)have impacts on adsorption effects of modified mangosteen shell charcoal on Ni(?),the order of Impacts from large to small is as follows:Cu(?)>Cd(?)>Pb(?).The adsorption model of Ni(?)by mangosteen shell biochar before and after modification is more in line with the Langmuir model.The two kinds of biochar adsorption reactions of Ni(?)are spontaneous endothermic reactions.The equilibrium time of Ni(?)adsorption by mangosteen charcoal before and after modification are 720 min and120 min,respectively.The adsorption process of Ni(?)by the two kinds of biochars is more in line with the pseudo-second-order kinetic equation,indicating that the adsorption on Ni(?)of these two kinds of biochars is mainly chemical adsorption.After measuring the Zeta potential of the mangosteen shell biochar before and after the modification,the pH_pzcof the mangosteen shell biochar was about 1.34,and the isoelectric point pH_pzcof the modified mangosteen shell biochar was about 3.36.Both hydroxy and carboxyl groups are involved in the adsorption of Ni(?)on the two kinds of biochars.During the adsorption of Ni(?)by the two kinds of biochar,Ni(?)may have ion exchange with some replaceable metal cations on the surface of the modified mangosteen biochar.Part of Ni(?)reacted with the-OH and-COOH on the surface of modified mangosteen charcoal,and existed on the biochar in the form of complexes or precipitates.(3)Research on the reuse of modified mangosteen shell biochar.The desorption effects of the three desorbents of HCl,HNO₃and NaOH at a concentration of 0.1 mol/L on Ni(?)are shown as follow in order of their effects as follows:HNO₃>HCl>NaOH,where the desorption amounts of HCl and HNO₃on Ni(?)are similar,and subsequent investigations are different The desorption effect of concentration of HCl and HNO₃on Ni(?),when the concentration of desorbent is 0.10 mol/L,the desorption rate of HCl on Ni(?)is 91.43%,and the desorption rate of HNO₃is 85.65%;When it is 0.15 mol/L,the desorption rate of HCl is 89.94%,the desorption rate of HNO₃is 90.64%,and the desorption effect of HCl with a concentration of 0.10 mol/L on Ni(?)is better.The best desorption time of HCl desorbent for Ni(?)is 2 h.Using HCl with a concentration of 0.1 mol/L as the desorbent,the modified mangosteen charcoal after adsorption of Ni(?)was desorbed at 30?for 2 h,and the resorption time was 24 h.After six adsorption-desorption cycles,the amount of Ni(?)adsorbed by modified mangosteen shell charcoal was 19.18 mg/g,which was reduced by 75.73%.Compared with other biochar,the amount of Ni(?)adsorbed by modified mangosteen shell charcoal Carbon has a good adsorption effect on Ni(?)and can be used repeatedly.