Activation of Red Clay for Adsorption of Dye and its Regeneration by Photo-Fenton Process

Today, industrial and sanitation wastewater production and their penetration into water resources have caused numerous challenges. Moreover, limitations on water resources used in industry, agriculture, drinking water, and wastewater have led human societies to make optimal use of available resources and treat the polluted water. This study investigated the effect of the acid and alkaline activation methods on dye adsorption by red clay. Each activated soil was used to remove methylene blue paint by adsorption method to determine the activated soil with the highest efficiency. The influential factors on adsorption, including the effects of solution pH (5-11), dye concentration (100-100 mg/L), and the amount of adsorbent (0.3-0.2 g) in adsorption of methylene blue dye, were examined on the optimal adsorbent, and the optimal conditions were investigated and determined. Then, X-Ray diffraction, measurement of porosity and effective surfaces, and Fourier transform infrared analysis were used to study the physical, chemical, and morphological properties. The results of chemical analysis showed that the soil activated with 3 M acid has the highest adsorption capacity among other activation methods. According to the detection analyses, the surface area of the clay increased after the acid activation operation due to  some of the bonds in the structure of the clay breaking (results of Fourier transform infrared) and the opening of the plates (scanning electron microscope images). These factors increased the uptake of activated soil significantly (27 to 81%) compared to raw soil. The adsorption behavior of the adsorbent showed that the adsorption isotherm is consistent with the Langmuir equation model. The results of the reusability study showed that the adsorbent is reusable. Results also showed that the modified soil is an effective adsorbent to remove methylene blue from aqueous solutions.