Biochar supported nano core-shell (TiO2/CoFe2O4) for wastewater treatment.

The porous structure of biochar, its large surface area, and its anti-oxidant properties are extensively used for pollutant removal strategies. The literature to date has reported that the biochar assisted metal-oxide core-shells have a dominating degradation ability under solar irradiation. Therefore, this study is significantly focused on cinnamon biochar as an active anti-oxidant agent incorporated in titania-cobalt ferrite nanocore-shell (Biochar/TiO2/CoFe2O4) structures for the first time in wastewater treatment against chlorophenol pollutants. Pure materials, core-shells, and biochar aided composites were synthesized by chemical methods, and their characteristics were analyzed using various instrumentation techniques. The diffraction outcomes of Biochar/TiO2/CoFe2O4 showed the mixed phases containing biochar, TiO2, and CoFe2O4. The morphological characteristics revealed that the biochar creates porosity and a peripheral layer covering the core-shell. Meanwhile, absorption studies of TiO2/CoFe2O4 core-shell and Biochar/TiO2/CoFe2O4 samples achieved 65% and 92% degradation efficiencies when exposed to visible light against chlorophenol pollutants, respectively. All these results confirm the presence of distinct functional groups as well as the combined synergistic effects that activated the charge separation, resulting in the successful destruction of water pollutants. In addition, the highly efficient Biochar/TiO2/CoFe2O4 sample was recycled, and the efficiency was maintained stable for five repeated degradation processes. Thus, Biochar/TiO2/CoFe2O4 will be utilized to expand the possibilities for biofuel generation and energy storage devices.

Spent coffee ground torrefaction for waste remediation and valorization.

Spent coffee grounds (SCGs) are a noticeable waste that may cause environmental pollution problems if not treated appropriately. Torrefaction is a promising low-temperature carbonization technique to achieve waste remediation, recovery, and circular bioeconomy efficiently. This study aims to maximize lipids retained in thermally degraded SCGs, thereby upgrading their fuel quality to implement resource sustainability and availability. This work also analyzes the lipid contribution to biochar's calorific value under various carbonization temperatures and times. Torrefaction can retain 11-15 wt% lipids from SCG, but the lipid content decreases when the pyrolysis temperature is higher than 300 °C. Extracted lipid content consisting of fatty acids echoed the results of diesel adsorption capacity. The lipid content in the biochar from SCG torrefied at 300 °C for 30 min is 11.00 wt%, and its HHV is 28.16 MJ kg-1. In this biochar, lipids contribute about 14.84% of the calorific value, and the other carbonized solid contributes 85.16%. On account of the higher lipid content in the biochar, it has the highest diesel adsorption amount per unit mass, with a value of 1.66 g g-1. This value accounts for a 22.1% improvement compared to its untorrefied SCG. Accordingly, torrefaction can sufficiently remediate SCG-derived environmental pollution. The produced biochar can become a spilled oil adsorbent. Furthermore, oil-adsorbed biochar (oilchar) is a potential solid fuel. In summary, SCG torrefaction can simultaneously achieve pollution remediation, waste valorization, resource sustainability, and circular bioeconomy.

Dual pretreatment of mixing H2O2 followed by torrefaction to upgrade spent coffee grounds for fuel production and upgrade level identification of H2O2 pretreatment.

Biochar is a carbon-neutral solid fuel and has emerged as a potential candidate to replace coal. Meanwhile, spent coffee grounds (SCGs) are an abundant and promising biomass waste that could be used for biochar production. This study develops a biochar valorization strategy by mixing SCGs with hydrogen peroxide (H2O2) at a weight ratio of 1:0.75 to upgrade SCG biochar. In this dual pretreatment method, the H2O2 oxidative ability at a pretreatment temperature of 105 °C contributes to an increase in the higher heating value (HHV) and carbon content of the SCG biochars. The HHV and carbon content of biochar increase by about 6.5% and 7.8%, respectively, when compared to the unpretreated one under the same conditions. Maximized biochar's HHV derived via the Taguchi method is 30.33 MJkg-1, a 46.9% increase compared to the raw SCG, and a 6.5% increase compared to the unpretreated SCG biochar. The H2O2 concentration is 18% for the maximized HHV. A quantitative identification index of intensity of difference (IOD) is adopted to evaluate the contributive level of H2O2 pretreatment in terms of the HHV and carbon content. IOD increases with increasing H2O2 pretreatment temperature. Before torrefaction, SCGs' IOD pretreated at 50 °C is 1.94%, while that pretreated at 105 °C is 8.06%. This is because, before torrefaction, H2O2 pretreatment sufficiently weakens SCGs' molecular structure, resulting in a higher IOD value. The IOD value of torrefied SCGs (TSCG) pretreated at 105 °C is 10.71%, accounting for a 4.59% increase compared to that pretreated at 50 °C. This implies that TSCG pretreated by H2O2 at 105 °C has better thermal stability. For every 1% increase in IOD of TSCG, the carbon content of the biochar increases 0.726%, and the HHV increases 0.529%. Overall, it is demonstrated that H2O2 is a green and promising pretreatment additive for upgrading SCG biochar's calorific value, and torrefied SCGs can be used as a potential solid fuel to approach carbon neutrality.

Recent advancements of spinel ferrite based binary nanocomposite photocatalysts in wastewater treatment.

A lot of studies on spinel ferrites (MFe2O4, M = divalent metal ion) and their binary nanocomposites as photocatalysts in the decontamination of wastewater have been performed, because MFe2O4 nanoparticles are relatively stable, biocompatible and low-cost efficient photocatalyst. The separation of MFe2O4 photocatalyst is easy owing to its excellent magnetic behavior. With this background, the recent developments on photocatalytic performances of MFe2O4 based binary nanocomposites were comprehensively reviewed. Especially, a focus on MFe2O4/metal oxides, MFe2O4/carbon based materials, MFe2O4/polymers, MFe2O4/metal nanoparticles and MFe2O4/other compounds for the photocatalytic degradation of dyes, emerging contaminants and inorganic pollutants has been thoroughly given. The advantages of MFe2O4 based nanocomposites as photocatalysts were also discussed. In addition, the possible pathway of active free radical generation by these photocatalysts under visible and ultraviolet irradiation has been explained. A comparison of photocatalytic activities of MFe2O4 based binary nanocomposites with recent reports has been carried out. This review concludes that MFe2O4 based binary nanocomposites have potential capacity in water purification technology. Nevertheless, their practical utilization in water treatment plants still needs to be further studied.