Dyeing wastewater is very hard to treat, and adsorption could be a good choice. Spent substrate of Pleurotus eryngii (SSPE) was first used to adsorb malachite green, safranine T and methylene blue from aqueous solutions, and the corresponding adsorption isotherm, thermodynamics and dynamics models were simulated. More than 93% of the dyes were removed with solutions with 100 mg/L of initial dye concentration, 1 g of SSPE and pH of 6.0 after adsorption for 4 h. Freundlich isotherm models fit better the adsorption data than Langmuir models. Adsorption of the dyes onto SSPE was a spontaneous exothermic process based on an adsorption thermodynamics model. SSPE could adsorb the dyes rapidly, and a second-order kinetics model fit better with the adsorption data than a pseudo first-order kinetics model. Accordingly, SSPE could be a good bio-adsorbent for the removal of malachite green, safranine T and methylene blue from the aqueous solution.

Brewer’s grains (BG), a by-product of the beer industry, were first pretreated by sulfuric acid, sodium hydroxide, and white-rot fungus Coriolus versicolor for the preparation of bio-adsorbents BGPH, BGPOH, and BGPB, respectively. All bio-adsorbents were rich in hydroxyl groups and could adsorb Congo red dye from aqueous solution, and BGPOH worked better than the others. The order of maximum equilibrium adsorption capacity of bio-adsorbents for Congo red was BGPOH > BGPH > BGPB. The Langmuir, Freundlich, and Temkin adsorption isotherm models all fit well with the experimental data. The negative Gibbs free energy change meant that the adsorption was spontaneous, and lower temperature was useful for the adsorption of Congo red onto the bio-adsorbents. The pseudo first-order and second-order kinetics models fit well with the experimental data, and the second-order kinetics model fit better, which indicated the adsorption was controlled by diffusion phenomena. Brewer’s grains with the three pretreatments could be used as efficient adsorbents for the treatment of dye wastewater.