Removal of Heavy Metal Ions by Poly(vinyl alcohol) and Carboxymethyl Cellulose Composite Hydrogels Prepared by a Freeze–Thaw Method

Abstract

Environmentally friendly composites made of poly­(vinyl alcohol) and carboxymethyl cellulose (PVA/CMC) hydrogels were proposed. The PVA/CMC hydrogels were prepared by freeze–thaw processes and applied to adsorb heavy metal ions including Ag+, Ni2+, Cu2+, and Zn2+. The phase separation of polymer solutions during freezing stages led to the formation of crystallites and resulted in insoluble hydrogels. The PVA/CMC hydrogels were effectively acquired, confirmed by at least 71% of insoluble gels found in the gel fraction. In addition, the gel fraction, physical properties, and swelling ratios were clearly modulated by the compositions of PVA and CMC among the samples of pure PVA, P2C1 (containing two-thirds of PVA and one-third of CMC), P1C1, and P1C2 hydrogels. For pure PVA hydrogels, the swelling ratio was 416%, while the P1C2 hydrogels exhibited a much higher swelling ratio (1437%). For the metal adsorption, the experimental results indicated that the P2C1 hydrogels presented not only the highest adsorption capacity toward Ag+ (8.4 mg per gram of hydrogel) but also the highest selectivity toward Ag+ in the mixed solutions. Interestingly, the experimental results revealed clearly that the adsorbed metal ions were further reduced on the P2C1 hydrogels. In summary, an insoluble hydrogel composed of PVA/CMC with excellent capacity of adsorbing metal ions was prepared in an economic and energy-saving manner. The prepared hydrogels showed potential applications for removal of heavy metal ions and wastewater treatment.

An Environmentally Benign Approach for As (V) Absorption from Wastewater Using Untreated Coffee Grounds—Preliminary Results

“…To facilitate the adsorption by the chemical bonding with anions, the surface of the absorbent should be made up of the cationic charge. However, since the surfaces of coffee grounds consist of functional groups such as hydroxyl, amino, and carboxyl groups showing the anionic charge [26][27][28], arsenate ions cannot interact with the coffee waste due to the repulsive interaction. The amount of absorbed arsenic element in this study might arise from the results of physical adsorption.…”

“…In addition, the disposed coffee wastes contain moisture and diverse organic matter, which produces harmful viruses and emits bad smells. As one of various methods to manage spent coffee wastes, the use of coffee wastes as an absorbent has been explored as a potential candidate for the extraction of heavy metal elements from wastewater, since the coffee grounds possess many pores to capture the specific matters and contain several functional groups including the hydroxyl and amino groups on the surface of the coffee, which makes specific substances absorbed by a chemical interaction [26][27][28]. For example, Azouaou et al demonstrated that the adsorption of cadmium was observed in aqueous solutions by using untreated coffee grounds [29].…”

Pineapple peel carboxymethyl cellulose/polyvinyl alcohol/mesoporous silica SBA-15 hydrogel composites for papain immobilization

“…However, due to indissolubility in most solvents, cellulose is generally converted to available derivatives by etherification (Takechi, Teramoto & Nishio, 2016). Among various kinds of cellulose derivatives, carboxymethyl cellulose (CMC) exhibits greatest potential use in food, paper, cosmetics, textile, pharmaceutical and paint industries owing to its good water solubility, biocompatibility and biodegrability Sommer et al, 2016;Wang & Wang, 2016).…”

“…Due to its non-toxicity, high hydrophilicity, biocompatibility and biodegrablility, PVA is extensively commercialized in the chemical and medical areas such as food, cosmetics, textiles, and pharmaceutics Wang & Wang, 2016;Zhang et al, 2015). PVA-based hydrogel can be formed by repeated freeze-thaw cycles, resulting in the formation of a polymeric network structure in which PVA crystallites provide physical cross-linking sites (Qi et al, 2015).…”

Adsorption Study of Pb(II), Cd(II), Hg(II) And Cr(III) Onto Calix[4]Resorcinarene Derivative

“…Various adsorbent has been reported in the removal of heavy metal ions. For instance, activated carbon 8 , zeolite 9 , polymer 10 , biosorbent 11 and macrocycle [12][13][14][15] .…”