[λ‑Carrageenan‑calcium phosphate] and [sodium alginate‑calcium phosphate] modified with dimethyl diallyl ammonium chloride and diallylamin co-polymer as efficient adsorbents of anionic dyes.

Alginate and carrageenan bio-polymers have been proved to be, only, good sorbents of cationic dyes. In this study, we reported the synthesis of [λ‑carrageenan‑calcium phosphate] and [sodium alginate‑calcium phosphate] modified with dimethyl diallyl ammonium chloride and diallylamin co-polymer, which could be used as effective adsorbents of anionic dyes. Evidence of chemical modification was proved through Fourier Transform Infrared Spectroscopy (FT-IR) band shifting, peaks broadening in X-Ray Diffraction (XRD) and the change in thermal event (TGA). The sorption process was studied using acid blue 25 as representative anionic dye. The adsorbed quantity reached, at equilibrium, 446 mg/g and 195 mg/g using cationized [sodium alginate‑calcium phosphate] and cationized [λ‑carrageenan‑calcium phosphate], respectively. However, it does not exceed 3.4 mg/g in the case of the unmodified [sodium alginate‑calcium phosphate]. The sorption of acid blue 25 using cationized hybrid materials complied well with the pseudo-second-order suggesting a chemi-sorption. Freundlich isotherm described well the adsorption mechanism of the three studied adsorbents. In summary, the high sorption capacities of the cationized hybrid materials obtained in this study suggest their use as effective adsorbents of acid dyes from wastewaters.