Removal of anionic and cationic dyes from aqueous solution using thermo- and pH-responsive amphiphilic copolymers

Amphiphilic copolymers exhibiting thermally induced phase segregation in water hold great potential as smart flocculants for water purification. Herein, we report the preparation of thermo- and pH-responsive copolymers based on oligo(ethylene glycol) methacrylate (OEGMA), dimethylaminoethyl acrylate (DMAEA) and pentafluorostyrene (PFS), and their use as thermally induced adsorbents for the removal of anionic and cationic dyes from water. The copolymer self-assembly behaviour in water was first studied as a function of concentration and pH. Then, the potential to remove thiazole yellow G (TYG) and rhodamine B (RhB) was investigated as a function of pH and dye concentration, highlighting that dye removal is mediated by hydrophobic and electrostatic interactions. As regards TYG, at pH 4 a removal capacity (RC) of about 80 mg/g, corresponding to a 97 % dye removal efficiency, was achieved at 800 mg/L TYG. In the case of RhB, a maximum RC value of 32 mg/g was obtained at pH 10. The results reported herein show that these copolymers represent a versatile platform to remove water-soluble organic dyes depending on pollutant concentration and pH conditions.