Study On The Removal Of Typical Pollutants In Water By Chitosan Stabilized Nano-silver Modified Tea Residue Biochar

Drinking water security is related to the national economy and people's livelihood,the important characteristic of water pollution in China is compound pollution,controlling compound pollution is very important for drinking water safety.The preparation of biochar from tea residue is suitable for its large quantity and low price,biochar is widely used in water purification.In this paper,chitosan and nano silver were used to modify tea residue biochar(the following is referred as "BC")to prepare chitosan stabilized nano silver modified tea residue biochar(the following is referred as "CsAgBC"),and the intermediate product nano silver biochar(the following is referred as "Ag BC"),then their physical and chemical properties were analyzed by physical and chemical characterization.Imidacloprid and methylene blue were used as typical pollutants for adsorption test,a several factors affecting the adsorption properties were discussed,adsorption kinetics and isothermal adsorption models were used to study the adsorption mechanism.To explore its application in the removal of cyanide and cadmium,preliminarily analyze the adsorption mechanism.The main conclusions are as follows:(1)Preparation and characterization of materials.The yield is inversely proportional to the carbonization temperature and carbonization time,the pH value is directly proportional to carbonization temperature.Description of physical and chemical characterization: Nano-silver particles have been uniformly loaded on the surface of CsAgBC,which have obvious Ag peaks.Before and after the modification,tea residue biochar showed amorphous carbon structure,with a large number of functional groups on its surface,the degree of graphitization remained basically unchanged,and their thermal stability are good.(2)The study on the removal of imidacloprid.CsAgBC has better adsorption performance than Ag BC and BC.pH=3 and the increase of temperature are favorable for adsorption.When the dosage of biochar increased,the adsorption capacity decreased and the removal rate increased.The adsorption kinetics and isotherm adsorption model study found that the adsorption behavior is chemical adsorption and monolayer adsorption,and the diffusion in particles is the main speed control step,and maximum adsorption capacity of monolayer is 2.13mg/g.The adsorption mechanism includes van der Waals force,?-? action,hydrogen bond action.(3)The study on the removal of methylene blue.CsAgBC has better adsorption performance than Ag BC and BC.pH>5 and the increase of temperature are favorable for adsorption.When the dosage of biochar increased,the adsorption capacity decreased and the removal rate increased.The adsorption kinetics and isotherm adsorption model study found that the adsorption behavior is chemical adsorption,monolayer adsorption and endothermic reaction,the adsorption process is mainly affected by the diffusion within the particles,and the maximum adsorption capacity of the monolayer is 28.10mg/g.The adsorption mechanism includes hydrogen bonding,?-? action and electrostatic action.(4)The application and exploration on the removal of cyanide and cadmium.The adsorption capacity of CsAgBC is better than that of unmodified biochar,it has better adsorption effect on cyanide and cadmium.The increase of temperature is farorable for the adsorption of cadmium by CsAgBC.The study of adsorption kinetics shows that the adsorption process of csagbc for cadmium is affected by internal diffusion of particles.In summary,chitosan stabilized nano-silver modified tea residue biochar,which contains the excellent properties of chitosan and nano-silver,is a new type of water purification material with the advantages of low price,high quality and borad spectrum,and has a good removal effection on a variety of pollutants.