Biopolymers Applied to Remove Metal Ions Through Ultrafiltration. A Review

Abstract

This manuscript is an overview of the versatile biopolymer materials alginic acid, carboxymethyl cellulose, and quaternized chitosan which contain different functional groups to remove hazardous inorganic species. These bioadsorbents are completely water-soluble and have a high versatility to achieve a higher sorption capacity and efficiency under different experimental conditions in combination with ultrafiltration membranes through the liquid-phase polymer-based retention (LPR) technique. In general, thesebioadsorbents are friendly with the environment and have a higher biodegradability compared with those more employed synthetic polymers.

Removal of Dyes by Polymer-Enhanced Ultrafiltration: An Overview

“…Consequently, a permeate with little or no presence of colorants is obtained [ 80 ] (see Figure 3 ). In general, water-soluble polymers can be classified into two categories: polyelectrolytes (polymers with charged groups in their repeating units) and polychelatogens (chelating polymers that contain chelating groups or complexes) [ 15 , 68 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ]. However, the most commonly used WSP for the removal of dyes in aqueous solution are polyelectrolytes.…”

“…However, the most commonly used WSP for the removal of dyes in aqueous solution are polyelectrolytes. These contain groups easily ionizable in water, such as -OH, -COOH, -NH 2 , -HSO 2 [ 28 , 68 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ], which are able to obtain polymers in solution with a positive or negative charge, called anionic or cationic polymers. The high content of functional groups contributes to the extractant properties of these compounds [ 28 , 95 , 96 ].…”

“…The high content of functional groups contributes to the extractant properties of these compounds [ 28 , 95 , 96 ]. The ionic nature of polyelectrolytes in solution generally induces electrostatic or ion exchange attractions between adsorbate–adsorbent [ 15 , 68 , 88 , 89 , 90 , 91 , 92 , 93 , 94 ]. The use of easily ionizable WSPs facilitates the uptake of acidic and basic dyes in the PEUF process, where acid dyes are attracted to cationic polymers and basic dyes to anionic polymers, respectively [ 2 , 72 , 75 ].…”

“…Where the dipole–dipole interactions between the polymer and water molecules are effective and, consequently, generate a greater interaction compared to the interaction between water–water molecules and/or polymer–polymer, so the polymer is solubilized in water [ 15 ]. Another requirement to consider is the molecular weight of the WSP, which must be higher than the MWCO of the UF membranes used in the process [ 15 , 28 , 88 ]. A molecular weight higher than the MWCO of the UF membrane favors the non-passage of WSP through it, avoiding its elution to the permeate [ 15 ].…”

Removal of Zirconium (Zr) from Aqueous Solution by Polymer Enhanced Ultrafiltration

“…Such polymers also have functional groups to bind ions/small molecules. In this process, unwanted ions/small molecules are first complexed by a polymer to increase their molecular weight with a size larger than the pores of the selected membrane that can be retained whereas permeate water is then purified from the unwanted molecules/ions [9][10][11][12].…”