Alginate-whey an effective and green adsorbent for crystal violet removal: Kinetic, thermodynamic and mechanism studies.

In this study, a novel biocomposite beads is developed by gelling sodium alginate (ALG) solutions in acid whey (Aw). The formation of alginate-whey biocomposite (ALG-Aw) was confirmed by FTIR analysis where the corresponding spectrum showed the presence of characteristic absorption bands of both ALG and Aw. SEM analysis showed the presence of lactic bacteria immobilized in the alginate matrix leading to the formation of new porous structure. The adsorption properties of adsorbents were evaluated in crystal violet dye (CV) removal from aqueous solutions using a batch adsorption technique. The results showed that the maximum adsorption occurred at pH 6 and for an adsorbent dose of 0.4 g/L. The kinetic of CV removal onto ALG-Aw adsorbent can be described well by the pseudo-second order equation. The equilibrium adsorption data of ALG-Aw followed well the Redlich-Peterson isotherm which is coherent with the calculated R, χ and ARE values. Calculated thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) shown that adsorption reaction is spontaneous and it is favored at low temperatures. Interactions of CV dye molecules with ALG-Aw composite beads were examined by FTIR and UV-visible DR spectroscopy.