Recycling of textile dye using double network polymer from sodium alginate and superabsorbent polymer

• A series of DNP were prepared with good swellability and dye recycling capacity.
• One gram of DNP absorbed 810 g of water and 439 mg of RB 4 dye in column mode.
• Dye adsorption obeyed Langmuir isotherm with pseudo-first-order kinetics.
• Unlike SAP, DNP had very good tensile and compressive strengths.
• DNP can serve as a good adsorbent for dye recycling from textile effluent.

Double network polymers (DNP) of different compositions were photosynthesized using sodium alginate (NaAlg) and superabsorbent polymer (SAP). They were characterized by FT-IR, thermal stability (TG), morphology by scanning electron microscopy (SEM), and its mechanical properties were also evaluated for their dye adsorption–desorption characteristics via adsorption isotherms at different temperature and pH values. The spectrophotometric determination of adsorbed dye indicated that the maximum dye uptake in column mode was 439 mg/g. The nearly identical visible absorption spectra of the fabrics dyed with virgin and recovered dyes indicated that the recovered dye retained its structural stability during column recovery and the dyed fabrics possess good color fastness properties. Dye adsorption kinetic and de-sorption mechanism were found to be pseudo-first-order and non-Fickian, respectively. The adsorption showed best fit for Langmuir adsorption isotherm. The changes in the thermodynamic parameters namely Gibbs free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) for the dye-adsorbent systems inferred that the adsorption process was spontaneous and exothermic.