Conversion of spent coffee grounds to biochar as promising TiO₂ support for effective degradation of diclofenac in water

Abstract

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.

A data synthesis on the biochar properties and implications for air, soil, and water quality in Brazil

“…Furthermore, biochar chemical modification or its use in composite materials can significantly increase removal efficiency of nutrients, toxic metals, and organic molecules (Nardis et al., 2021; Souza et al., 2020). Also, biochar anchored with Ti oxides has been used for adsorption and photocatalytic degradation of organic molecules (Lazarotto et al., 2020).…”

Recent progress in TiO2–biochar-based photocatalysts for water contaminants treatment: strategies to improve photocatalytic performance

“…In addition, it can be adopted that TiO 2 and biochar are mixed by manual mechanical grinding, followed by calcining to prepare the composites. For instance, Lazarotto et al 107 pyrolyzed the mixture of spent coffee biomass and TiO 2 via manual mechanical mixing to prepare biochar–TiO 2 composites. In the procedure, the biomass was converted into TiO 2 -impregnated biochar.…”

Trends in removal of pharmaceuticals in contaminated water using waste coffee and tea‐based materials with their derivatives

“…This process is quite interesting considering that the adsorbed drug gets mineralized prior to the saturation of the adsorption active sites, which keeps the process ongoing and yield a more complete removal process for pharmaceuticals in water. Elsewhere, a biochar derived from spent coffee grounds with immobilized TiO 2 was applied as a photocatalyst for degradation of diclofenac (Lazarotto et al, 2020). In this case, 90% degradation efficiency was achieved within 120 min where 1,3-dichlorobenzene was produced as a by-product.…”

“…Removal of water pollutants including pharmaceuticals through the degradation process, which converts drugs into smaller molecules has been reported (Kumar et al, 2019, Mlunguza et al, 2019). Both coffee and tea‐based materials have been modified for applications in degradation of pharmaceuticals (Chen et al, 2022; Huo et al, 2020; Lazarotto et al, 2020; Zhang, Shen, et al, 2022). For the degradation of tetracycline, coffee grounds were used as carbon source during the preparation of N, S ‐doped porous carbons for persulfate activation, sodium bicarbonate as pore‐forming agent, while L ‐cysteine monohydrochloride allowed for dual doping of sulfur and nitrogen atoms (Huo et al, 2020).…”