Research On The Removal Of Heavy Metal Ions And Dye Wastewater By Modified Peach Kernels

Nowadays,water pollution becomes more and more serious with the continuous development of industrialization.Especially,industrial effluents containing heavy metals and organic dyes have caused serious harm to human health and life.Consequently,it's urgent to find an efficient method to remove heavy metals and organic dyes from wastewater.Biosorption is a new water treatment method and has broad research prospects due to its considerable advantages,such as high removal efficiency,low cost,abundant sources of adsorption materials and without secondary pollution.Therefore,in recent years,researchers have paid more and more attention on this novel water treatment method.In this paper,peach stones,a kind of forestry and agricultural residues,were chosen as raw materials to prepare two new modified peach stone adsorbents through chemical modification.During the chemical process,citric acid(CA)and ethanediamine(EDA)were respectively used as the modifier.To study the adsorption properties of the two new adsorbents in detail,they were respectively employed to remove different heavy metals and organic dyes.The main research and conclusions are as follows:(1)Using CA and EDA to modify peach stones and optimizing the experimental preparation conditions by single factor experiment,the results showed that MPS had the maximum carboxyl group content,5.44 mmol/L,with 0.8 mol/L CA,reaction temperature of 120? and reaction time of 4 h.And the N content of EPS had the maximum,0.7076%,with 1.25 mol/L EDA,reaction temperature of 60? and reaction time of 4 h.(2)The peach stones before and after modification were characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),elemental analyzer,thermal gravity analysis(TG)and surface area analyzer.The results showed that the structure,performance and appearance of peach stones all had relative changes after being modified by CA and EDA respectively.(3)In adsorption experiments,the adsorption capacities of heavy metals(Cu2+,Cd2+,Pb2+)and methylene blue(MB)by MPS and the adsorption capacities of Cr(?)and congo red by EPS were investigated.And the absorption capacities of peach stones before and after modification were compared and the influences of factors on adsorption were studied.The results indicated that the amount of heavy metals and MB on PS were significantly enhanced after being modified by CA.And the adsorption effects of MPS to Cu2+and Pb2+are optimal when pH is 5,and to Cd2+ and MB,the best adsorption effects was obtained when pH is 6;and the adsorption effects of MPS to heavy metals(Cu2+,Cd2+,Pb2+)and MB are better when the adsorbent dosage is 4 g/L.It can be found that coexisting ions have different influences on adsorption process of MPS and the adsorption capacity of heavy metals(Cu2+,Cd2+,Pb2+)and MB decreased with the increase of coexisting ions concentration.Moreover,the results showed that the uptake of Cr(?)and congo red also were significantly enhance after modification by ethylenediamine.And the adsorption effects of EPS to Cr(?)is the best at pH 2.5 and to congo red at pH 4.When the adsorbent dose is 3 g/L,EPS have better adsorption effects to Cr(?)and congo red.It can be found that coexisting ions have different influences on adsorption process of EPS and the adsorption capacity of Cr(?)and congo red.decreased with the increasing coexisting ions concentration,but the coexisting ions Na+and K+can improve the adsorption capacities of congo red.(4)The adsorption kinetics of heavy metals and dyes by MPS and EPS were studied through the analysis of pseudo-second-order and intra-particle diffusion models.The results showed that the adsorption process of heavy metals and MB by MPS followed better pseudo-second-order and also obeyed well intra-particle diffusion models,and the experimental data of Cr(?)and congo red by EPS can be fitted well by pseudo-second-order model,which indicated that the adsorption process of MPS and EPS was mainly controlled by chemical adsorption and can be affected by ion exchange.(5)The Langmuir and Freundlich isotherm models were employed to investigate the adsorption isotherm models of heavy metals and dyes by MPS and EPS.The results showed that the experimental data of heavy metals by MPS can be fitted well by Langmuir and Freundlich isotherm models,but the experimental data of MB by MPS can be fitted well by Freundlich isotherm model,which indicated that the adsorption process of heavy metals and MB by MPS is a complex adsorption process.For the adsorption process of Cr(?)and congo red by EPS,they can follow the Langmuir isotherm model well indicating that the adsorption process of them can be monolayer adsorption.And the maximum adsorption capacities of Cu2+,Cd2+,Pb2+and MB by MPS were 32.22,37.48,118.76,178.25 mg/g respectively,and the maximum uptakes of Cr(?)and congo red by EPS were 24.68 and 31.49 mg/g respectively.(6)The desorption experiments of MPS and EPS were performed with 0.01 mol/L HCl and NaOH respectively.Results indicated that MPS and EPS all still had some adsorption capacities of heavy metals and dyes after being recycled for four times.And NaOH will be better for the regeneration of EPS after adsorption of congo red.