Study On Adsorption Of Cd(?) And Cr(?) In Water By Modified Medical Stone

With the wide production and application of cadmium,chromium and its compounds in industry,a large amount of cadmium and chromium contaminated by cadmium and chromium into the water is becoming more and more serious.Medical stone is a porous medicinal rock that is non-toxic,harmless and biologically active,it can effectively improve its ability to remove ions from heavy metals such as cadmium and chromium in water with physical and chemical other means modified stone as adsorbent,and it has the advantages of simple operation process and simple equipment and low cost.This paper takes Shandong Mengyin medical stone as raw materials,dosage of medical stone and Cd(?),Cr(?)initial concentration as a variable for medical stone on the cadmium,chromium and other heavy metal ions in the water absorption test,to determine the suitable dosage of medical stone and the optimal initial concentration of Cd(II)and Cr(VI);Four kinds of different physical and chemical methods were used to modify the medical stone,such as particle size modification,heat treatment modification,sulfuric acid modification,manganese dioxide modification,to carry out modified preparation process optimization study;Explores the medical stone size,heat treatment modification temperature,time,sulfuric acid concentration,dosage of sulfuric acid,sulfuric acid acidification modification time,manganese dioxide is generated and the mass ratio of maifan stone,aging time,dosage of modified manganese dioxide,heavy metal ion solution pH value and other factors on the adsorption of Cd(?)and Cr(?)in water;Before and after modification of medical stones were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and NOVA 2000 e automatic specific surface area and porosity analyzer,using inductively coupled plasma emission spectroscopy(ICP-OES)detected the adsorption of Cd(?)and Cr(?)in water,studying the thermodynamics and kinetics of the adsorption of Cd(II)and Cr(VI)by manganese dioxide modified medical stone.It provides a new idea and method to further improve the added value of medical stone mineral and its adsorption and purification of Cd(II)and Cr(VI)in water.The main conclusions of this paper are as follows:(1)Characterization of natural medical stone and modified medical stone and found that the main mineral composition of medical stone before and after modification is the same,mainly composed of albite and quartz;medical stone after modification by manganese dioxide coated with a layer of black manganese oxide;The specific surface area,pore volume and pore size of the modified medical stone were increased to some extent,which was more favorable for the adsorption of Cd(?)and Cr(?).(2)Combined with the adsorption rate and adsorption capacity of Cd(?),Cr(?)and the time of static contact adsorption for 24 hours,the suitable dosage of natural medical stone was 20 g,Cd(II),Cr(VI)the optimal initial concentration is 50mg/L,the adsorption rate was 65.01% 42.76%.(3)The smaller the particle size,the greater the specific surface area of the medical stone,the higher the adsorption rate of Cd(?)and Cr(?),considering the adsorption rate and the difficulty of pumping and washing,considering the adsorption rate and filter the difficulty and other factors,this paper chooses 160-200 mesh medical stone adsorption experiments were carried out on the Cd(II),Cr(VI).the adsorption reached 70.82% and 55.74% respectively.(4)The adsorption rate of Cd(?)and Cr(?)in water was 93.31% and 74.5%,respectively,when the temperature was 400 ? and the treatment time was 2h.(5)when the concentration of sulfuric acid is 1 mol/L,treatment of sulfuric acid,sulfuric acid consumption of 100 ml,when time is 60 min effect is better in the sulfuric acid modified medical stone,the Cd(?),Cr(?)adsorption rate reached 94.12%,77.98% respectively.(6)When the formation of manganese dioxide and medical stone mass ratio of 7:20,aging time 24 h,modified amount of calamine 3g,the pH value was 6.02 and 6.07 respectively in The process of manganese dioxide modified medical stone,the Cd(?),Cr(?)adsorption rate reached 98.62%,92.58% respectively.(7)The adsorption isotherm equation and kinetic equation of Cd(II)and Cr(VI)in water were removed by manganese dioxide modified medical stone,the results show that the modified medical stone on Cd(II),Cr(VI)adsorption is more suitable for Langmuir(Langmuir)isotherm model to describe the adsorption process that manganese dioxide modified medical stone is monolayer adsorption,thus calculated Gibbs free energy G is less than zero,indicating the modified medical the stone of Cd(II),Cr(VI)adsorption was spontaneous and exothermic reaction;manganese dioxide modified medical stone on Cd(II),Cr(VI)in the process of adsorption kinetics is consistent with the quasi two level dynamic equation,which can influence the prediction time on adsorption process.