The Application And Performance Of Bentonite And Cellulose-Based Adsorbents

Environmental issues are increasing people’s attention and concern, especially water pollution problem, because it directly affects the safety of drinking water and human health. Adsorption in a variety of water treatments is a low-cost, simple and highly effective method, so it has often been applied to treat wastewater. Natural adsorbents can’t reach the desired adsorption effect owing to the limited adsorption capacity, therefore, modifying natural adsorbent material to improve its adsorption properties has become a hot research in the world. In this paper, the adsorbents were designed and synthesized by using natural bentonite or cellulose, and studied their adsorption performance of pollutants from water. Specific works are as follows:1. The removal of ionic liquid (1-butyl-3-methyl imidazolium chloride:BMImCl) was studied from aqueous solution by raw bentonite, acid-activated bentonite and organic-modified bentonite. These types of bentonite sample were characterized by FT-IR, TGA and XRD. The effects of contact time, BMImCl initial concentration, pH, ionic strength, and humic acid on the removal of BMImCl were investigated via batch adsorption experiments. The adsorption kinetics models were applied to predict the adsorption constants, and the kinetic data indicated that the pseudo-second-order model gave a better fit. Furthermore, the Langmuir, Freundlich and Temkin isotherms models were also introduced to describe adsorption process in order to obtain possible mechanism of the removal. The applied isotherms models demonstrated that the adsorption data of acid-activated bentonite samples was well described by Temkin adsorption isotherm, and the isotherm model of organic-modified bentonite was Langmuir adsorption isotherm.2. Cellulose modified with maleic (M) and phthalic (P) anhydride, to be named CMA and CPA, were tested as feasible adsorbents for the removal of malachite green from aqueous solution. At the same time, the uptake ability of natural cellulose was also studied for comparison. The structure of material was characterized by FT-IR and XRD. The effects of solution pH, initial dye concentration, contact time and temperature were investigated in detail by batch adsorption experiments. The kinetic and isotherm studies suggested that the adsorption followed the pseudo-second-order model and Langmuir isotherm. The maximum adsorption capacity on CMA and CPA were 370 mg g-1 and 111 mg g-1, respectively. Furthermore, the thermodynamics studies indicated the spontaneous nature of adsorption of malachite green on adsorbents.3. The acid-activated bentonite (AB) was again modified by the boehmite sol, obtained the modified bentonite (AB-BS), and studied their adsorption behavior for the removal of malachite green from aqueous solution. AB and AB-BS were characterized by FT-IR, SEM and XRD. The effects of pH, contact time, initial concentration and ionic strength on the removal of malachite green were investigated via batch adsorption experiments. The adsorption kinetic and isotherm models were investigated to explain the adsorption mechanism. The experimental results showed that the adsorption process is a rapid and effective process.