Preparation And Performance Study Of Bentonite-Based Organic Dye Wastewater Treatment Agent

With the rapid development of printing,food,medicine and dyeing industries,the green and pollution-free treatment of organic dyestuffs has become an increasingly serious problem for human beings.Dye wastewater not only contains a wide variety of dyes and separate difficultly,but also has a strong biological toxicity,which is easily carcinogenic and mutagenic.Among the many treatment methods for organic dye wastewater,adsorption has become the most commonly used wastewater treatment method by virtue of low cost,easy operation process and less environmental pollution.Unfortunately,most adsorbents have expensive price in the wastewater treatment process which limited their applications.Therefore,there is an urgent need to find cost-effective adsorbent materials.Researchers have found that bentonite,a clay mineral,is a novel and environmentally friendly adsorbent material that can be used to remove harmful substances from wastewater and does not re-pollute the environment after adsorption.However,the layer spacing and cation exchange capacity of natural bentonite are low.Therefore,it is important to modify bentonite by a series of modification means to change its low performance status.Based on the pore structure and surface properties of bentonite,this thesis uses a series of modification reagents to modify bentonite based on the pore structure and surface properties of bentonite,on the one hand,to improve the montmorillonite content and surface modification as a starting point;on the other hand,bentonite is used as a raw material and it is compounded and doped with other materials.The specific research of this thesis is as follows.（1）High-purity bentonite was obtained by modifying bentonite with sodium pyrophosphate and anhydrous sodium carbonate to increase its montmorillonite content,and the effect of modified bentonite on MB adsorption performance under different experimental conditions was investigated.The experiments revealed that the adsorption capacity of the sodium bentonite was four times that of the natural bentonite and twice that of the purified bentonite,and its adsorption rate was 99.89%.The adsorption of MB by sodium bentonite was more consistent with the Langmuir model and PFO kinetic model.The adsorption of MB by sodium bentonite is mainly surface electrostatic adsorption and interlayer domain ion exchange interaction,but also some intermolecular force adsorption.The characterization results showed that sodium bentonite have larger SA,PV and CEC than natural and purified bentonite,and have abundant hydroxyl structures.（2）The effects of organic poly-carboxylic acid type,addition ratio and different experimental conditions on the CR adsorption performance of modified bentonite were investigated by modifying bentonite with oxalic acid and citric acid needles and adding carboxyl functional groups to the surface of bentonite.The results revealed that the capture capacity of CR was ranked from largest to smallest:HB-N0.25>HB-C1.5>bentonite.Langmuir and PSO kinetic model will better describe the adsorption behavior of HB-N0.25on CR,and its adsorption capacity could reach 336.45 mg·g^-1.The adsorption of CR on poly-carboxylic acid is a chemical process of chelation,hydrogen bonding and immobilization.chemical process controlled by the active adsorption sites（-OH and-COOH）on the adsorbent surface.（3）By using bentonite as perforation agent and silicon source,it was compounded with magnesium silicate,which was named MS-Bt.The paper mainly investigated the effects of bentonite doping,hydrothermal time and hydrothermal temperature on the adsorption MB properties of magnesium silicate composites.MS-Bt synthesized under optimal conditions was significantly more effective than bentonite and magnesium silicate for MB adsorption.The Langmuir and PSO kinetic model can better describe the MS-Bt’s The adsorption behavior of MS-Bt can reach 253.92 mg·g^-1.MS-Bt changes the original microporous structure of magnesium silicate partially into a mesoporous structure,increasing the specific surface area in contact with the dye and better adsorption of MB.