Study Of Heavy Metal Ion And Dyes Molecular Adsorption Onto Adsorbents Prepared From Glycyrrhiza Residue By Chemical Modification

With the development of traditional Chinese medicine, more and more the Chinese medical residues are produced in the production process of Chinese medicine. Currently, they are disposed through combustion or land filling, which produces secondary pollution easily and waste resource, so that it has brought some thorny problems to the manufacturer, society and environment. Therefore, carrying out the comprehensive utilization of the residue resources has important practical significance.In this study, glycyrrhiza residue(GR) was modified with H2SO4, KOH and H3PO4. The optimum conditions for production of adsorbents were obtained from single factor experiments based on the yield and Pb2+adsorption value of the products. The main preparation conditions such as the concentration of H2SO4, KOH and H3PO4, ratio of solid to liquid, modified temperature and modified time on the influence of the adsorbent’s adsorption ability were studied. The structure and morphology of glycyrrhiza residue and modified glycyrrhiza residue were characterized by lots of instruments, such as BET-N2 adsorption,FTIR and SEM. Also the physical and chemical characteristics such as SBET and functional groups were examined. And then, the products were used to adsorb four heavy metal ions(Pb2+、 Cd2+、 Zn2+and Ni2+) and two dyes(Crystal violet and Methyl orange) from simulatedwaste water. By using batch adsorption techniques, the influence of p H, adsorbent dosage,adsorption time on adsorption effect was investigated. In addition, adsorption kinetics and adsorption isotherms were studied.The experimental results were showed as follows: when the glycyrrhiza residue was as raw material, the concentration of H2SO4 was 15 mol/L, the ratio of solid to liquid was 1:6,the temperature was 95℃, and the modified time was 10 h, the products(SGR) had the yield of between 40 % and 50 %, as well as the adsorption percentage was 97.43% for Pb2+; The concentration of KOH was 70%, the ratio of solid to liquid was 1:5, the activation temperature was 700℃, and the activation time was 30 min, the activated carbon(CAC) had the yield of between 30 % and 40 %, the adsorption percentage above 98% for Pb2+. The concentration of H3PO4 was 70%, the ratio of solid to liquid was 1:8, the activation temperature was 500℃,and the activation time was 45 min, the activated carbon(PAC) had the yield of between 40 %and 50 %, the adsorption percentage was about 93% for Pb2+.The results of SEM showed that the CAC and PAC become rough porous in structural morphology, surface area was increased, the surface area of CAC and PAC was 583.1m2/g,513.7m2/g accordingly,which is greater than the industrial water treatment activated carbon level standard( 500 m2/g). For FTIR and functional groups analytics which improved the number of actived functional groups. The XRD patterns showed that CAC and PAC prepared by KOH and H3PO4 direct activation have the predominantly amorphous structure of carbons.After the H2SO4 modified, the appearance of morphology was smooth. Due to the molecular surface reaction with sulfuric acid, making-SO3 H into the glycyrrhiza residue, IR spectrum analysis also suggests that-SO3 H on the surface of SGR.The three kinds of adsorbents were used for adsorption treatment of four heavy metal ions(Pb2+、 Cd2+、 Zn2+and Ni2+) and two dyes(Crystal violet and Methyl orange) from simulated wastewater, respectively. The adsorption experiment results showed that the adsorbents had certain removal efficiency for the heavy metal ions and dyes. According to theLangmuir equation, the adsorption capacity for heavy metal ions and dyes on the modified glycyrrhiza residue increased compared with the GR and also much higher than some other adsorbents reported in literature. The adsorption process of SGR, CAC and PAC was fitted the Pseudo-Second-Order equation. The loaded adsorbents were regenerated using 0.1 mol/L HCL solution and could be used repeatedly for five times with little loss of adsorption capacity.This paper provides important found mental date for the effective reuse of glycyrrhiza residues and their applications for heavy metal ion and dyes wastewater treatment.