In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Treatment of wastewater is becoming a concern of an increasing prominence. Trace amounts of toxic metalloids and heavy metals (HMs) would contaminate large volumes of water. Being present as traces, removal of these ultratrace contaminants from wastewater is challenging. Adsorption of HMs onto raw (RPP) and burnt (BPP) potato peels (PP) is presented in the current treatise. Both adsorbents (RPP and BPP) proved to be efficient in removing Cd(II), Co(II), Cu(II), Fe(II), La(III), Ni(II), and Pb(II) from aqueous solutions. BPP was a more efficient adsorbent compared to RPP. Ecodesign of amodel, greenadsorbent was structured executing a multivariate approach, design of experiments (DoE). The purpose of using DoE is to maximize the efficiency of BPP (carbonaceous biomass) as a versatile adsorbent. Plackett–Burman design (PBD) was used as a screening phase. Four factors were considered: pH, contact time (CT), heavy metal concentration (HMC), and the adsorbent dose (AD). The Pareto chart of standardized effects shows that the most influential factor is the HMC. These data were confirmed by analysis of variance (ANOVA). Derringer’s function was operated to find the best factorial blend that maximizes the adsorption process. The percentage (%) removal of Cd(II), for example, was maximized hitting 100%. Adsorbent surface characterization was performed using FTIR, BET, SEM, TGA/dTG, and EDX analyses. Adsorption was found to be physisorption that follows Temkin isotherm with sorption energy 66 kJ/mole. Adsorption kinetics was found to be pseudo-first-order. Adsorption capacity (q_m) for BPP was 239.64 mg/g. The diffusion inside the particles was very limited, while the initial rate of the adsorption was extremely high as shown by the Elovich plot.

Alkoxysilanes and organoalkoxysilanes are primary materials in several industries, e.g. coating, anti-corrosion treatment, fabrication of stationary phase for chromatography, and coupling agents. The hydrolytic polycondensation reactions and final product can be controlled by adjusting the hydrolysis reaction, which was investigated under a variety of conditions, such as different alkoxysilanes, solvents, and catalysts by using gas chromatography. The hydrolysis rate of alkoxysilanes shows a dependence on the alkoxysilane structure (especially the organic attachments), solvent properties, and the catalyst dissociation constant and solubility. Some of the alkoxysilanes exhibit intramolecular catalysis. Hydrogen bonding plays an important role in the enhancement of the hydrolysis reaction, as well as the dipole moment of the alkoxysilanes, especially in acetonitrile. There is a relationship between the experimentally calculated polarity by the Taft equation and the reactivity, but it shows different responses depending on the solvent. It was found that negative and positive charges are respectively accumulated in the transition state in alkaline and acidic media. The reaction mechanisms are somewhat different from those previously suggested. Finally, it was found that enthalpy–entropy compensation (EEC) effect and isokinetic relationships (IKR) are exhibited during the hydrolysis of CTES in different solvents and catalysts; therefore, the reaction has a linear free energy relationship (LFER).

Adsorptive removal of rose bengal (RB) from contaminated water samples was approached using pineapple leaves (PAL). Three adsorbents were utilized for that purpose; raw pineapple leaves (RPAL) and the thermally activated bio-waste leaves at 250 and 500 °C. Two measures were executed to evaluate the functionality of exploited biomasses; percentage removal (%R) and adsorption capacity ($q_e$). Face-centered central composite design (FCCCD) was conducted to experiment the influence of variables on the %R. Dose of PAL as adsorbent (AD), concentration of RB (DC), pH and contact time (CT), were the inspected factors. Existence of functional groups and formation of activated carbon was instigated employing Fourier-transform infrared (FT-IR) and Raman spectroscopies. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses were used to explore surface features. Thermal behavior of adsorbents was studied using thermogravimetric analysis (TGA). The surface area and other surface structural properties were established using the Brunauer Emmett-Teller (BET) analysis. An amount of 92.53% of RB could be removed with an adsorption capacity of 58.8 mg/g using a combination of pH 5.00 ± 0.20, RPAL dose of 0.05 mg/50 mL, and 10-ppm RB for 180 min. Equilibrium studies divulge a favorable adsorption that follows the Freundlich isotherm. Pseudo-second-order model explains the observed adsorption kinetics.