The assessment of sorption properties of protein-polysaccharide complexes of brown algae Laminaria digitata and Saccharina latissima under a biorefinery concept

In this study the waste (protein-polysaccharide complexes (PPC)) after integral processing of brown algae Laminaria digitata and Saccharina latissima was used as novel biosorbent for dyes (methyl orange and methylene blue) removal. The effect of different concentrations (10-250 mg/L), contact time (5-120 min), temperature (27-47 degrees C), and pH (2-10) on adsorption efficacy were evaluated. The highest sorption capacities were obtained under optimal temperature/pH conditions: 37 degrees C and pH 6 (methyl orange) and pH 10 (methylene blue). Adsorption of cationic methylene blue is significantly higher than of anionic methyl orange which indicates negative surface charge of the adsorbent. The experimental adsorption data followed the pseudo-first- and pseudo-second-order kinetics and were best represented by the Langmuir and Sips models. Thermodynamically, the adsorption process is endothermic (low concentrations) and exothermic (high concentrations). The possible mechanism of adsorption is complex and includes chemical (through binding with the - OH, - COOH, - NH 2 groups) as well as physical interaction of dyes with the capillary-porous and fibrous surface of PPC. The obtained results highlight the potential of the studied protein-polysaccharide complexes as biosorbents.

Automated summary

In this study, waste from integral processing of brown algae was used as a biosorbent for dye removal. The highest sorption capacities were achieved under optimal temperature and pH conditions. The experimental data followed pseudo-first- and pseudo-second-order kinetics and were best represented by the Langmuir and Sips models. The results highlight the potential of protein-polysaccharide complexes as biosorbents.