Methylene Blue Removed from Aqueous Solution by Encapsulation of Bentonite Aerogel Beads with Cobalt Alginate

Abstract

It can be difficult to remove dark methylene blue (MB) from water effectively. The use of sodium alginate and bentonite (Ben) as the matrix produced a displacement reaction that occurred in cobalt chloride, which allowed Ben to be successfully encapsulated in cobalt alginate (CA). Finally, a vacuum freeze-drying method was used to prepare a low-cost composite of CA/Ben aerogel for adsorbing MB in aqueous solutions. In addition to scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy, the composites were also characterized and analyzed. Different adsorption experiments were conducted in order to determine the effects of dosage, pH, adsorption time, and temperature on the adsorption performance of the adsorbent. According to the results of the experiment, the adsorption capacity of CA/Ben aerogel was 258.92 mg·g-1, and the pseudo-first-order kinetic model and Freundlich isotherm model can fully explain the adsorption process of MB on this aerogel. The composite material reported in this paper is easily recycled, and the removal rate reaches 65% after four times of recycling. Moreover, compared with other adsorbents, the composite material of the invention is highly environmentally friendly and has a simple preparation process. A large-scale application of this technology is the removal of dyes from water on a large scale.