Preparation and characterization of algae-based biopolymer nanocomposite hydrogels for the adsorptive-photocatalytic degradation of malachite green dye.

This study combines experimental synthesis with molecular dynamic (MD) simulations to investigate the molecular level interactions governing the formation of the microalgae Ba/starch hydrogel. A molecular model representing the experimentally synthesized hydrogel was constructed, and Monte Carlo (MC) and MD simulations were performed to predict and validate the interfacial interactions and thermodynamic affinity between Ba and the starch matrix. Based on these computational insights, the purpose of this study is to prepare a highly absorbent hydrogel from microalgae and biopolymers for removing malachite green dye (MG) from wastewater via photodegradation. In this work, microalgae (Ba) + starch (Ba + St) hydrogel, microalgae Ba + chitosan (Ba + Cs) hydrogel, and Ba + St + Cs hydrogel are used as model substrates for the photocatalytic degradation of MG dye under solar radiation with a variety of reaction conditions. The surface and compositional changes of the produced photocatalyst were studied with XRD, FTIR, SEM, and UV-vis spectrophotometers in relation to the MG dye photodegradation, irradiation time, catalyst dose, dye concentration, and pH. The findings demonstrated that the decomposition progressed consistently from 5 to 360 minutes of irradiation time, reaching 11% to 99% for Ba + St hydrogel degradation and from 6% to 36% for Ba + Cs hydrogel and from 33% to 72% for Ba + St + Cs. This results from the MG dye molecule contact with the photocatalyst surface. The longer the irradiation period, the more the MG dye molecules interacted with the photocatalyst surface. As a result, the photocatalyst photodegradation efficiency increased. To reach a quicker rate of degradation, intervals of 360 minutes are employed.