▎ 摘　　要

NOVELTY - Hydroxygraphene-nano-silica modified chitosan composite material is prepared by adding hydroxylated graphene and nano-silica into acetone to obtain a mixed solution, stirring, dripping hydrochloric acid, adjusting the pH value, dripping epichlorohydrin, controlling the temperature, stirring the mixed solution at 50-60 degrees C for 5-10 hours after dripping, and distilling in vacuum to remove acetone and epichlorohydrin to obtain the first reactant, and (b) adding chitosan to isopropanol to obtain a reaction solution, adding sodium hydroxide to it in batches, controlling the temperature of the reaction solution at 30-50 degrees C, adding the first reactant obtained in step (a) to it under stirring, continuously stirring for 10-15 hours, filtering, washing the filter cake with water, then washing with an organic solvent, and drying in vacuum. USE - The composite material is used in a sewage treatment and a sewage treatment agent (all claimed). ADVANTAGE - The composite material is a grid structure with large molecular structure and strong adsorption capacity, adsorbs various pollutants in sewage, such as protein, carbohydrate, fat, urea or ammonia nitrogen, and the structure contains a large number of amino groups and hydroxyl groups, which effectively adsorbs heavy metal ions in water through chelation reaction. In addition, the pi - pi stacking in the structure of the raw material hydroxylated graphene adsorbs aromatic or benzene ring-containing organic small molecules. The composite material breaks the limitation that the conventional water treatment agent only adsorbs and removes a single nitrogen-rich or phosphorus-rich nutrient element, and improves the removal effect of single nitrogen-rich or phosphorus-rich nutrient elements. The raw material provides synergistic effect. DETAILED DESCRIPTION - Hydroxygraphene-nano-silica modified chitosan composite material is prepared by adding hydroxylated graphene and nano-silica into acetone to obtain a mixed solution, starting stirring, dripping hydrochloric acid, adjusting the pH value of the mixed solution to 2-4, dripping epichlorohydrin, controlling the temperature of the mixed solution to be below 40 degrees C during dripping, stirring the mixed solution at 50-60 degrees C for 5-10 hours after dripping, and distilling in vacuum to remove acetone and epichlorohydrin to obtain the first reactant, where the mass ratio of hydroxylated graphene, nano silica, acetone and epichlorohydrin is (0.3-0.5):(5-8):(210-230):(20-25), and (b) adding chitosan to isopropanol to obtain a reaction solution, adding sodium hydroxide to it in batches, controlling the temperature of the reaction solution at 30-50 degrees C, adding the first reactant obtained in step (a) to it under stirring, continuously stirring for 10-15 hours, filtering, washing the filter cake with water, then washing with an organic solvent, and drying in vacuum to obtain hydroxygraphene-nanosilica modified chitosan, where the organic solvent is a mixed solution of dichloromethane and isopropanol, and the mass ratio of chitosan, isopropanol, sodium hydroxide, hydroxylated graphene, water, and organic solvent in step (a) is (8-12):(190-210):(2-2.5):(0.3-0.5):(280-320):(280-320). INDEPENDENT CLAIMS are included for the following: (1) use of a hydroxygraphene-nano-silica modified chitosan composite material in sewage treatment; and (2) a sewage treatment agent comprising 80-100 pts. wt. hydroxylgraphene-nano-silica modified chitosan composite material, 20-30 pts. wt. modified starch, 10-20 pts. wt. activated carbon, 5-10 pts. wt. ferrous sulfate, 2-5 pts. wt. nano zinc oxide and 20-30 pts. wt. polyacrylamide.