Synthesis Of Lignin-based Dithiocarbamate And Its Adsorption Performance Towards Heavy Metal Ions

The harm of heavy metal on the environment and human has becoming more and more serious, it is important to develop a new heavy metal adsorption material. Dithiocarbamate (DTC) is a kind of organic compound which containing N and S coordination atoms, DTC has a good adsorption properties of heavy metal ions, but it is expensive, toxic and difficult to biodegradation. Lignin next to cellulose, is the second most abundant natural raw material, so we anchor DTC groups onto alkali lignin matrix, in order to develop an environmental friendly, high efficiency and low cost of the new recapture agents, the results are as follows:(1) Lignin-based dithiocarbamate (LDTC) is synthesized by using alkali lignin, diethylenetriamine and carbon disulfide through Mannich and Esterification reaction. The effect of factors on yield are investigated, the yield is increased at first and then decreased with the increase amount of alkali lignin, diethylenetriamine and carbon disulfide, meanwhile, rise the temperature and extend the reaction time is benefit to improve the yield. IR analysis shows that the new absorption peaks at 1112、960 and 1430 cm-1, which can be assigned to the stretching vibrations of the C= S、C-S and-NCSS- group, respectively, indicating that the DTC group successfully grafted onto the alkali lignin, XPS analysis shows that the amount of N and S is 15.65% and 7.35% respectively, which is higher than lignin.(2) The adsorption properties for Cu2+and Pb2+by LDTC is investigated, the results show that the saturated adsorption capacity is 175.9 and 103.4mg/g respectively, and the adsorption processes followed second-order type kinetics and the adsorption rate controlled by chemisorption; the adsorption isotherm for Cu2+is in line with the Freundlich model and Langmiur model, which shows that the adsorption of Cu2+is monolayer adsorption, the adsorption isotherm for Pb2+is in line with the Langmiur model, which shows that the adsorption of Pb2+is monolayer adsorption; the removal rate can reach more than 98% when dealing with the 50mg/L of heavy metal ions in wastewater at a dosage of 0.025g/50mL.(3) Nano-materials have the advantage of small particle size, large specific surface area and high surface energy, in this paper, it is the first time to use lignin as raw material and synthesis nano lignin-based dithiocarbamate (nano-LDTC) by using the inverse suspension method, the effect of factors on its particle size distribution are investigated, the results show that:the increasing of stirring rate, the ratio of liquid paraffin and water and the amount of emulsifiers, reducing the amount of cross-linking agent can decrease the particle size distribution; SEM shows that the nano-LDTC is uniform distributed and the main particle size is distributed between 200-300nm, the surface analyzer indicates the surface area can reach 23.75 m2/g.(4) The adsorption capacity of nano-LDTC toward Cu2+and Pb2+is investigated, the results show that the saturated adsorption capacity is 211.5 and 288.04mg/g respectively, the adsorption processes followed second-order type kinetics and the adsorption rate controlled by chemisorption; the adsorption isotherm for Cu2+and Pb2+are in line with the Langmiur model, which show that the adsorption for Cu2+and Pb2+ are monolayer adsorption; the removal rate can reach more than 99% when dealing with the 50mg/L of heavy metal ions in wastewater at a dosage of 0.02g/50mL.