Effective Parameters on the Formation of Natural Zeolite-Based Granules to Remove Cationic Dyes from Contaminated Water

Methylene blue and crystal violet dyes are the most widely used dyes in some industries such as textiles, silk, and wood. Accumulation of cationic dyes in water resources is harmful to humans, animals, and the environment, so their removal from the effluents of the dyeing industry is essential. Among all the treatment methods, adsorption is one of the most attractive routes for the treatment of polluted water due to its low cost and simplicity of design. According to the studies, it can be seen that zeolites modified with iron nanoparticles show a high adsorption capacity in the removal of dyes. However, the use of adsorbents in the form of fine powders is still difficult and their use in continuous systems is limited due to the cracking and the pressure drop.

To solve the problems of adsorbents in powder form, the ionic gelation method was used to prepare a granular adsorbent based on natural zeolite clinoptilolite modified with Fe3O4 nanoparticles. In order to prepare granules with suitable appearance and high adsorption percentage, the effect of various parameters such as initial pH of the solution, type and concentration of the crosslinking solution and initial ratio of alginate to nanocomposite was investigated. The synthesized granules were investigated by XRD, SEM-EDX and BET analysis.

The results showed that the pH was ineffective and the iron (III) chloride solution was optimal with a concentration of (2 w/v%) and an initial ratio of 1:4 alginate to nanocomposite. The maximum adsorption capacity of the prepared granules towards methylene blue and crystal violet adsorption was determined as 12.484 mg/g and 11.904 mg/g by Langmuir isotherm, respectively, which indicated to a high ability of the prepared granules to remove these cationic dyes.