Preparation Of Self-floating Amphoteric Adsorbent And Its Adsorption Performance For Dyes

In recent years,with the rapid development of industry,more and more industrial waste water is produced and discharged into natural water,so the problem of water pollution is becoming more and more serious.Dye wastewater is an important source of water pollution.The dyes discharged into water is difficult to biodegrade,which often hinders the penetration of sunlight and oxygen,thus inhibiting the photosynthetic activity of aquatic system and causing serious environmental problems.In addition,dyes has strong carcinogenicity,teratogenicity,mutagenicity and toxicity,which poses a serious threat to human beings and aquatic organisms.Therefore,the treatment of dye wastewater is very necessary.Compared with other processes,the adsorption process for dye wastewater treatment is both economic and efficient,which is easy to run and does not produce toxic and harmful substances.The property of adsorbents is an important factor affecting the effect of adsorption treatment.As a new type of granular material,hollow glass microspheres（HGM）has good stability and can be modified,which is an ideal carrier of adsorbents.The main component of HGM is Si O₂.HGM can attach different functional groups through modifying,which greatly improves the application range of HGM.The research on HGM surface modification technology has been reported,but it is seldom used in wastewater treatment engineering.HGM has a large specific surface area because of hollow structure.What’s more,HGM can achieve self-floating and accumulate on the water surface because of its low density.The strong separation ability is conducive to the follow-up（e.g.solid-liquid separation,adsorption recovery and reuse）,so it can be used as a new carrier of water treatment agent and has a broad application prospect.In this study,the self-floating adsorbent Am-SA was prepared,and its characterization,adsorption performance,and mechanisms were studied.The main research contents and conclusions are as follows:（1）HGM were pretreated with high concentration of Na OH to obtain HSM,then grafted with silane coupling agent A-1100 to prepare amphoteric adsorbent Am-SA that can spontaneously complete the floatation and solid-liquid separation on the surface.The synthesis method is simple and feasible.（2）The morphology,structure and chemical properties of Am-SA were characterized by SEM,XPS,XRD,Zeta potential,EDS,TGA and particle size.The results showed that Am-SA presented regular spherical shape,and A-1100 was grafted successfully;During the pretreatment process,the Si-O bond is destroyed,which increases the amount of Si-OH;With the increase of p H,the Zeta potential of Am-SA decreased significantly;Morever,Am-SA had good thermal stability and low density,which could realize self-floating separation in 30 min.（3）The adsorption performance of Am-SA for AO7 was studied.When the p H value increased,the adsorption capacity decreased significantly.When the p H value was2,the adsorption effect was the best,and the maximum adsorption capacity was88.13mg/g;The adsorption reaction of Am-SA on AO7 basically reached equilibrium at5min.SO₄^2-、NO₃^-and Cl^-competed with AO7 for adsorption,but when the ion concentration was low,the effect was small.Langmuir isotherm model had the best fitting correlation,indicating that the reaction was monolayer adsorption;PSO adsorption kinetic model had the best fitting effect,which showed the reaction was mainly controlled by chemical adsorption mechanism;ΔH>0,ΔS>0 andΔG<0,indicated that the reaction was endothermic and spontaneous.The adsorption capacity of Am-SA for AO7 still reached 75%of the initial equilibrium adsorption capacity after five times cycles.The FTIR results of the adsorbents before and after adsorption indicated that the amino group on the surface of Am-SA played an important role in the adsorption of AO7,and the main mechanism of adsorption of AO7 by Am-SA was electrostatic action.（4）The adsorption performance of Am-SA for CV was studied.When the p H value increased,the equilibrium adsorption capacity increased significantly.When the p H value was 10,the adsorption effect was the best,and the maximum adsorption capacity was 567.40 mg/g;The adsorption reaction of Am-SA on CV basically reached equilibrium at 1000min.Na⁺、K⁺and Ca²⁺competed with CV for adsorption,but when the ion concentration was low,the effect was small.Langmuir isotherm model had the best fitting correlation,indicating that the reaction was monolayer adsorption;PSO adsorption kinetic model had the best fitting effect,which showed that the reaction was mainly controlled by chemical adsorption mechanism;ΔH>0,ΔS>0 andΔG<0,indicated that the reaction was endothermic and spontaneous.The adsorption capacity of Am-SA for CV still reached 86%of the initial equilibrium absorption capacity after five times cycles.The FTIR results of adsorbents before and after adsorption indicated that the silane hydroxyl group in Am-SA played an important role in the adsorption of CV,and the main mechanism of adsorption of CV by Am-SA was electrostatic action.（5）Compared with other adsorbents,the adsorption capacity of Am-SA for AO7and CV is relatively high.Am-SA can remove AO7 and CV efficiently.Besides,Am-SA is p H responsive and has amphoteric characteristics,which can be separated from the surface and easily regenerated.Therefore,Am-SA is expected to be applied in the treatment of amphoteric dye wastewater.