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An anionic, low-cost, and environmentally friendly composite PVA/Agar/Bentonite (PAB) hydrogel was prepared via self-assembly method, then evaluated as an adsorbent for both cationic methylene blue (MB) and anionic Congo red (CR) dyes using static (batch adsorption) and dynamic (column filtration) procedures. The structural/textural and morphological features of the hydrogel were investigated by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, zeta potential measurements and scanning electronic microscopy. The nonlinear forms of first-order and second-order kinetic model, and nonlinear forms of Langmuir–Freundlich, Redlich–Peterson, Langmuir and Freundlich isotherm model were used to study the equilibrium adsorption. The adsorption kinetics of MB and CR dyes onto composite hydrogel followed the nonlinear form of pseudo-second-order model with the adsorption capacity of 107.45 and 42.05 mg/g, respectively. The equilibrium data were fitted well to the nonlinear Langmuir–Freundlich model for MB dye and nonlinear form of Langmuir model for CR dye, which were confirmed by R2, MSE and EABS values. Using the column purification method, the composite hydrogel PAB promotes the removal of the MB and CR pollutants by maintaining the concentrations of the filtrate solutions below 0.1 mg/L, even when the volume of the dye reaches 20 mL.

The dispersion of anatase TiO2 on diatomic material was a prospective route to avoid agglomerates of these particles. In this work, the TiO2/diatomite composites were prepared using a solvothermal process and a non-hydrolytic sol-gel method at low temperature on the raw (TDB) and the purified (TDS) diatomite. The synthesized samples were characterized utilizing various techniques. These given that TiO2 anatase was impregnated well on the surface of diatomite, and the immobilization of these particles tends to increase the thermal stability of the composite as compared to the raw diatomite. In addition, the photodegradation of crystal violet (CV) in solution was in the direction of TDB > TDS > TiO2. The 99.996% of CV can be degraded in 210 min of irradiation time at pH 10. These results revealed that the immobilization of titanium on diatomite improves the photocatalytic degradation by reducing the crystallite size of anatase TiO2.

The aim of this work was to study the photocatalytic degradation of Methylene Blue and phenol by nano-particles coated on diatomite as a new nano-composite catalyst. Titanium dioxide (Degussa P25) was immobilized on diatomite powder at different compositions by a very simple and low cost technique. Diatomite powder (also called Kieselguhr) is an Algerian substance with a snow-white color and porosity greater than 72%. High porosity allowed the diatomite powder to float on the surface of water providing a means for the treatment process that enabled separation from water without any need for pumping as well as the exposure to solar radiation when supported beneath titanium dioxide (TiO2) during photocatalysis. The morphology characterization of the prepared catalysts was carried out by X-ray diffraction analysis, scanning electron microscopy and infrared spectroscopy (IR). Photocatalytic activity was initially tested in a single reactor followed by pH, conductivity and absorbance analyses. Photocat...