Biosorption of methylene blue by residue from Lentinus crinitus mushroom cultivation.

Conventional textile effluent treatments cannot remove methylene blue, a mutagenic azo dye, and an endocrine disruptor, that remains in the drinking water after conventional water treatment. However, the spent substrate from Lentinus crinitus mushroom cultivation, a waste, could be an attractive alternative to remove persistent azo dyes in water. The objective of this study was to assess the methylene blue biosorption by spent substrate from L. crinitus mushroom cultivation. The spent substrate obtained after mushroom cultivation had been characterized by the point of zero charge, functional groups, thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Moreover, the spent substrate biosorption capacity was determined in function of pH, time, and temperature. The spent substrate had a point of zero charge value of 4.3 and biosorbed 99% of methylene blue in pH from 3 to 9, with the highest biosorption in the kinetic assay of 15.92 mg g- 1, and in the isothermal assay of 120.31 mg g- 1. Biosorption reached equilibrium at 40 min after mixing and best fitted the pseudo-second-order model. Freundlich model best fitted the isothermal parameters and each 100 g spent substrate biosorbed 12 g dye in an aqueous solution. The spent substrate of L. crinitus cultivation is an effective biosorbent of methylene blue and an alternative to removing this dye from water, adding value to the mushroom production chain, and supporting the circular economy.

Sugarcane biomass colonized by Pleurotus ostreatus for red 4B dye removal: a sustainable alternative.

Biosorption of the red 4B dye was evaluated using non-colonized sugarcane bagasse and colonized by Pleurotus ostreatus. The fungal colonization caused an increase in the acid and phenolic groups, making the biosorbent surface more positive, with lower thermal stability due to decomposition of lignocellulosic compounds, lower pHpcz, and smaller pores. The biosorbents showed better adsorption at pH 2.0 and required 260 min to reach equilibrium. The kinetic data fit the pseudo-second order mathematical model, which predicts strong chemical interaction between adsorbent and adsorbate. The mathematical models that best fit the isothermal data were the combination of Langmuir for low dye concentrations and Freundlich for high dye concentrations in the solution for the non-colonized biosorbent, which predict that adsorption occurs in monolayer and multilayer, respectively. For the colonized biosorbent, the model that best fits the isothermal data (25°C and 40°C) was the Freundlich model, showing that the adsorption for this case occurs in multilayers. Thermodynamic studies (25°C, 40°C and 50°C) show that increasing temperature decreases the biosorption capacity (exothermic process for both biosorbents), and the system shows low spontaneity with increasing concentration. Also, the entropy for non-colonized sugarcane bagasse increases at low concentrations, however after fungal colonization, it decreases for both. In industrial effluent, the non-colonized biosorbent presented a higher biosorption capacity, but fungal colonization demonstrates greater sustainability by initially allowing the production of mushrooms.