Trends of Dye Removal and Heavy Metal Removal of Different Hydrogel-Based Materials and Their Mixtures

Hydrogels are relatively newly developed materials that has piqued the curiosity of scientists in various fields, particularly for wastewater treatment applications. Heavy metal ions and dye removal hydrogels is becoming more popular due to its ease of use, low cost, increased effectiveness, biodegradability, and reusability. Evaluate and study the adsorption behaviour of different hydrogel materials towards heavy metal ions and dyes. The hydrogels investigated are Poly(2-Acrylamido-2-Methylpropane Sulphonic Acid) (PAMPS) hydrogels, commercial sodium polyacrylates (Na-PA), chitosan (CH), along with their binary and ternary mixtures. A semi-interpenetrating network (IPN) based on PAMPS and Na-PA was also investigated. The performance of each hydrogel towards six different heavy metals (Co+2, Cu+2, Ni+2, Cd+2, Zn+2, and Mn+2), cationic Methylene Blue (MB) dye, and anionic Methyl Orange (MO) dye, was studied and analysed. It was found that the Na-PA/CH hydrogel was the best performing hydrogel for heavy metal removal, removing more than 84% of all metals, followed by PAMPS/Na-PA which removed up to 70%. The best hydrogel mixture with both cationic and anionic dyes is PAMPS/CH, removing 90.1% and 85%, respectively. The proposed dye removal mechanism is electrostatic attraction between the dyes and the charged functional groups on the hydrogel’s surface. It is concluded that the use of Na-PA with CH for heavy metal removal yields better results than when using each hydrogel separately. For dye removal, it was found that combining PAMPS with CH creates a very promising hydrogel suitable for removing both anionic and cationic dyes, which is critical for industrial applications.