In this study, Acid Blue 25 (AB25), which is a negatively charged synthetic dye was removed from an aqueous solution by adsorption onto agricultural wastes, including banana (BP) and durian (DP) peels. The adsorption performances of AB25 were related to surface characteristics of the agricultural wastes, including their chemical functional groups, net surface charge, surface morphology, surface area, and pore volume. Parameters affecting the adsorption, including contact times, initial concentration, pH, and temperature were investigated. The results revealed that the adsorption of AB25 followed pseudo-second order kinetics, and that the adsorption process was controlled by a combination of intraparticle and film diffusion with a two-step mechanism. The equilibrium data could be simulated by the Langmuir isotherm model, suggesting that AB25 molecules are adsorbed on active sites with a uniform binding energy as a monolayer on the adsorbent surface. The adsorption process was spontaneous and exothermic, and the adsorption capacity decreased with the pH of the medium. The spent adsorbents were best regenerated by acid treatment (pH 2), and could be recycled for several adsorption-desorption processes. Under ambient conditions, the maximum adsorption capacities of AB25 on BP and DP were 70.0 and 89.7 mg g−1, respectively, which is much higher than on a large variety of reported adsorbents derived from other agricultural wastes.

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There is a need to develop alternative disinfectants that differ from conventional antibiotics to address antibacterial resistance, along with specialized materials for biomedical applications. Herein, we report on the synthesis of zinc sulfide (ZnS) capped with chitosan (CS) to produce CS-ZnS nanocomposites (NCs), which were assayed for antibacterial activity in liquid handwash formulations. The CS-ZnS NCs were prepared using the bottom-up wet-chemical method. The role of CS as the capping agent was investigated by varying the ratio of CS with respect to the ZnS precursor. The prepared CS-ZnS NCs were characterized using complementary spectral methods: scanning electron microscopy–energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The antibacterial activities of liquid handwash (LH) formulations containing 1% (w/w) CS-ZnS NCs were tested against Staphylococcus aureus and Escherichia coli using the agar diffusion test method. This LH formulation displayed antibacterial activity against S. aureus with an average inhibition zone diameter in the range of 16.9–19.1 mm, and met the quality standards set by the National Standardization Agency. The formulated LH solutions containing CS-ZnS NCs showed antibacterial activity, which suggests that the CS-ZnS NCs have potential as an alternative active ingredient for tailored and non-irritant antibacterial LH detergents.

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