Preparation Of Some Modified Bentonites And Their Adsorption Performance To Environmental Pollutants

With the rapid development of industrial production,disposal of a large amount of industrial wastewater have seriously polluted eco-environment in the world.Among the ways to treat pollution wastewater,adsorption method is one of the most widely used methods because of its many merits,such as simple operation,low cost,high treatment efficiency,fast treatment speed and no secondary pollution.Therefore,the investigation and preparation of new-type effective adsorbent have also become a researching hotspot.As we know,natural clay mineral,bentonite,possesses abundant reserves,widespead sources,low cost and good adsorption performance and has become one of the most popular natural sorbents.But due to its strong hydrophilicity and monotony of the adsorption site and mechanism,its adsorption performance for organic dyes and heavy metal ions needs to be further improved.So a functionalized modification for bentonite structure is very important.Therefore,in this thesis,natural bentonite was chosed as a raw material,four kinds of novel bentonite based composites were prepared by different modified processes and their adsorption properties to different pollutants were studied.It mainly consists of three parts as follows:1.A composition adsorbent SDS-BT was successfully prepared through modifying bentonite?BT?using cationic surfactant,sodium dodecyl sulfate?SDS?and characterized by FT-IR,SEM,TG and XRD and its adsorption properties to methylene blue?MB?,malachite green?MG?and crystal violet?CV?were studied in detail.The results domonstrated that formation of the SDS-BT intercalation composite effectively increased dispersity and specific surface area of the composite and provided more paths for sorption of the target molecules,as a result,improved adsorption performance of the composite to these three dyes.The maxmum adsorption capacities for MB,MG and CV reached 555.54 mg/g,665.32 mg/g and1334.54 mg/g,respectively,indicating a good application potential.The adsorption equilibrium data obeyed Langmuir isotherm and the kinetic data fitted well pseudo-second-order equation,which indicated that the adsorption of the dyes on the adsorbent followed a monolayer chemisorption mechanism,drived simultaneously by electrostatic interaction and partition between the adsorbent and the adsorbate.2.A composition sorbent CTAB-Na-BT of intercalationstructure was synthesized by re-modifying sodium bentonite pre-prepared by an ion exchange process using cationic surfactant,cetyl trimethylammonium bromide?CTAB?,characterized and applied to remove of methyl orange dye in simulated dye wastewater.The results showed under optimal experimental conditions,the maxmum decolorization rate of the wastewater reached 99.65%and the maximum adsorption capacity was 276.9mg/g.And the study on adsorption equilibrium and on adsorption kinetic displayed that the adsorption followed Langmuir isotherm adsorption model and pseudo-second-order kinetic model,which belonged to a chemically controlled monolayer sorption mechanism.Thermodynamic study proved that the sorption was a spontaneous and endothermic process.3.By using chitosan?CTS?and?2,3-epoxypropyl?trimethylammonium chloride?GTMAC?to modify sodium bentonite,a binary sorbent?CTS-Na-BT?and a ternary sorbent?GTMAC-CTS-Na-BT?were respectively prepared and their structures,morphologies and adsorptive properties to Pb²⁺were investigated.The results demonstrated that these two adsorbents possessed excellent adsorption performance for Pb²⁺and under optimized conditions,their maxmum adsorption capacities were87.94 mg/g and 91.81 mg/g,respectively with a good application prospect.