The production of the edible mushroom Agaricus bisporus occurs on a world scale, where tons are constantly produced. At the same time, this production generates a large amount of waste that needs to be adequately conditioned. Therefore, mushroom residues were used to develop activated carbon for the removal of 2,4-D-the developed adsorbent showed a microporous structure with several spaces on the surface. The FTIR analysis showed that the activated carbon has functional groups such as aromatic rings, carboxylate, hydroxyl. It was found that the optimum adsorption of the 2,4-D occurs at pH 4 and adsorbent dosage of 0.4 g L−1; The equilibrium data were better fitted to the Freundlich model. However, for calculating the thermodynamic parameters, it was considered the Langmuir equilibrium constant (KL). The value of Langmuir Qmax was 241.7 mg g−1 at 298 K. The thermodynamic behavior indicated a spontaneous and favorable, and exothermic. The magnitude of the adsorption enthalpy is in agreement with physical adsorption. System equilibrium was attained before 30 min regardless of 2,4-D concentration. The kinetic curves showed good statistical adjustment to the linear driving force (LDF) model, with capacity values close to the experimental ones (qexp = 194.6 mg g−1; qpred = 187.3 mg g−1), at 100 mg L−1 of 2,4-D. The adsorbent removed up to 70% of the simulated effluent when using the Jacuí river as the sample. Regeneration studies showed that the activated carbon could be used up to 9 times without losing significant efficiency. Last, the process cost production was estimated to be 2.39 USD kg−1 of activated carbon. Therefore, it can be concluded that activated carbon developed from edible mushroom residues is a promising alternative as an adsorbent for the treatment of actual effluents containing 2,4-D herbicide.
A novel composite, biochar derived from spent coffee grounds with immobilized TiO2 (biochar–TiO2) was prepared, characterized, and applied as an alternative, effective, and sustainable photocatalyst for degrading diclofenac from aqueous solution. Composites with different mass ratios between TiO2 and biochar were prepared by mechanical mixing and subsequent pyrolysis in an inert atmosphere of N2 at 650°C. The sample with biochar–TiO2 ratio of 1:1 presented a degradation efficiency of 90% at just 120 min versus 40% for TiO2 used as reference. This fact is associated with a set of intrinsic characteristics obtained during the formation of the composite, such as superior pore size, avoiding the recombination of the ē/h+ pair, bandgap reduction, and promotion of reactive oxygen species due to phenolic groups present on the biochar surface. The dominant reactive species involved during the photocatalytic degradation of diclofenac were h+ and •OH. The diclofenac degradation pathways were determined based on the identification of intermediates and nonpurgeable organic carbon (NPOC) analysis. The novel biochar–TiO2 composite prepared in this work showed high physical–chemical stability and efficiency over five consecutive cycles of reuse, proving to be a highly promising photocatalyst for degrading diclofenac in water.
The production and consumption of cassava (Manihot esculenta) occur in several places worldwide, producing large volumes of waste, mostly in the form of bark. This study sought to bring a new purpose to this biomass through producing activated carbon to use as an adsorbent to remove the herbicide Diuron from water. It was observed that the carbon contains the functional groups of methyl, carbonyl, and hydroxyl in a strongly amorphous structure. The activated carbon had a surface area of 613.7 m2 g−1, a pore volume of 0.337 cm3 g−1, and a pore diameter of 1.18 nm. The Freundlich model was found to best describe the experimental data. It was observed that an increase in temperature favored adsorption, reaching a maximum experimental capacity of 222 mg g−1 at 328 K. The thermodynamic parameters showed that the adsorption was spontaneous, favorable, and endothermic. The enthalpy of adsorption magnitude was consistent with physical adsorption. Equilibrium was attained within 120 min. The linear driving force (LDF) model provided a strong statistical match to the kinetic curves. Diffusivity (Ds) and the model coefficient (KLDF) both increased with a rise in herbicide concentration. The adsorbent removed up to 68% of pollutants in a simulated effluent containing different herbicides. Activated carbon with zinc chloride (ZnCl2), produced from leftover cassava husks, was shown to be a viable alternative as an adsorbent for the treatment of effluents containing not only the herbicide Diuron but also a mixture of other herbicides.
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