Research On Preparation Of Activated Carbon From Lees And Treatment Of Wastewater Containing Pb²⁺ And Cd²⁺

The yield of Chinese lees is greatly,and it’s widely used in the production of feed and fertilizer.The treatment method of lees is single,and it is easy to corrupt with a lot of packing quantity,so it is necessary to develop and utilize the waste lees from various aspects in order to prevent the waste of resources.In this paper,the study on the preparation of activated carbon from lees,not only provides a new way for the utilization of lees,but also provides a scientific basis for the development and research of activated carbon.In this paper,activated carbon was prepared by KOH activation method,and the iodine sorption value,methylthionine chloride sorption value,yield,specific surface area,surface oxygen-containing functional group,distribution of pore size,the treatment effect of wastewater containing cadmium and lead were used as indices.The optimum conditions were explored by single factor and orthogonal experiment.The activated carbon was modified by oxalic acid,and the treatment effect of wastewater containing cadmium and lead by the activated carbon were used as indices.Single factor experiment was used to explore the optimal modification conditions.The functional groups,specific surface area and pore size,element content,scanning electron microscopy,XRD and sorption kinetics of activated carbon before and after modification were compared and analyzed,in order to research the modified effect of activated carbon from lees.The results show that:(1)The optimum preparation conditions of activated carbon from lees: the carbonization temperature was 450℃(the carbonization time was 0.5h);The concentration of KOH solution was 60%,the solid-to-liquid ratio of lees and KOH solution was 1: 5,the activation temperature was 700℃,the activation time was 2.0h.(2)The optimum conditions of activated carbon modified by oxalic acid : The modification time was 3h,oxalic acid concentration was 0.08g/m L,the modification temperature was 30℃.(3)The mass of activated carbon modified by oxalic acid was decreased;The adsorption value of the activated carbon decreased,the iodine sorption value reduced by3.74%,and the methylthionine chloride sorption value reduced by 5.97%.The total number of acidic functional groups on the surface of activated carbon modified by oxalic acid was 1times higher than that before modification.Among them,the content of phenolic hydroxyl group had the maximum amplification,the increase of carboxyl content was nearly doubled,and the change of lactone group content was minimal.After activated carbon was modified by oxalic acid,the pore size was significantly increased,and the specific surface area,porevolume,average pore size and total volume of micropores were decreased,but the removal efficiency of cadmium and lead ions was greatly increased with the increase of acid functional groups.The content of N and H in the activated carbon increased slightly after oxalic acid modification,the content of C was decreased,and the content of S was reduced from less than1% to less than 0.1%.(4)After activated carbon was modified by oxalic acid,the pseudo first-order and pseudo second-order kinetic equilibrium adsorption capacity qeof activated carbon on cadmium ion and lead ion increased,and the adsorption rate constant k also increased.The in-diffusion rate of kWin Weber-Morris was decreased.The adsorption of cadmium ion and lead ion by activated carbon before and after modification was more consistent with the Langmuir model,which was mainly the monolayer adsorption.Pseudo second-order kinetic model was more suitable to describe the adsorption of cadmium and lead ions by the activated carbon from lees before and after modification.