Study On Adsorption Of Industrial Printing And Dyeing Wastewater By TEMPO-oxidized Reed Straw

In this study,a novel biosorbent is prepared that agricultural and forestry waste reed straw is used as matrix,ultrasonic treatment,sodium hydroxide immersion and TEMPO-Na Br-Na Cl O oxidation are selected to their surface modification.And modern analytical instruments is used to analysis its morphology and surface functional groups.The adsorption behavior of four cationic dyes of methylene blue,crystal violet,neutral red and malachite green in industrial wastewater is studied,and the adsorption mechanism is discussed.The regenerative properties of the adsorbent are also investigated.The main research work and the results are as follows:(1)The preparation and characterization of the modified reed strawIn this study,the optimum synthesis process of the new nano-cellulose adsorbent is determined by single factor control,that is,the ultrasonic treatment was carried out for 2 min,then immersed in 10% Na OH solution,finally,the TEMPO-Na Br-Na Cl O system was oxidized at 45 ℃.SEM and FT-IR are used to characteriz the surface structure morphology.SEM characterization results indicate that reed straw has multiple fibrous structure which is conducive to adsorption;FT-IR showed that active groups(O-C=O)significantly increased after TEMPO compound modification,indicating that the modification changed the elemental composition of the surface of the straw.The grafting of carboxy was successfully grafted to the reed straw.(2)Static adsorption of Dye on TEMPO compound-modified reed strawThe static experimental results of adsorption of TEMPO compound-modified reed straw on methylene blue,crystal violet,neutral red and malachite green show that modified reed straw has the best removal efficiency which can reach 99.61%,96.48%,98.26% and 99.20%,respectively,when the adsorption temperature is at 25℃,concentration of the adsorbent dosage is 1.0g/L,1.5g/L,1.5g/L and 1.5 g/L,respectively,p H is 9.0,6.2,4.2 and 4.7,respectively,the initial concentration is 200mg/L,400mg/L,300mg/L and 600mg/L,respectively,adsorption time is 300 min,300min,240 min and 180 min,respectively.(3)Adsorption kinetics and mechanism for cationnic dyes onto modified reed strawThe results for experimental data applying dynamics eqations pesudo-first-order,pseudo-second-order,Elovich and intraparticle diffusion eqation show that the adsorption for four kinds of cationic dyes conforms to the pseudo-second-order kinetic model,confirming that the adsorption rate is controlled by chemical sorption.The isotherms model of cationic dyes on the modified reed straw indicate that Langmuir isotherm equation gives better fit than Freundlich and Temkin isotherm confirming that the adsorption for dyes is in monolayer.The results of FT-IR analysis showed that the carboxyl group grafted onto the surface of the reed straw is the active group for the adsorption.(4)Research of regeneration performance of modified reed strawThe results showed that the adsorbent adsorbed by HCl,H2SO4 and HNO3 could be desorbed and regenerated under the condition of H2O2 as the catalyst.The regenerated adsorbent still maintained a high removal rate of the dyes,indicating that the novel adsorbent has a good regeneration performance.