Low-cost biochar was derived from corncob Zea mays L. cultivated in Northern Thailand for animal feed by facile synthesis with in-house modified pyrolysis for 2 h at ∼500 °C, ∼10 °C min⁻¹ heating rate. Fixed-carbon, ash, %CHNSO and volatile contents of biochar were characterized and compared with pristine biomass. Thermal analysis was performed to monitor the transition of corncob biomass to biochar under the pyrolysis conditions. The physicochemical properties of biochar were investigated by scanning electron microscopy and FT-IR analysis, indicated honeycomb structure on the biochar surface with cylindrical pores and various functional groups, such as carbonyl and phenolic groups. Methylene blue adsorption in aqueous solution by biochar was studied at 25 °C. Without any chemical activation on biochar, the maximum removal efficiency of methylene blue by biochar was 16.50 mg g⁻¹. Effect of the initial concentration and the contact time on removal of methylene blue was studied to archive optimal conditions. The equilibrium adsorption of methylene blue on the biochar was well fit by the Langmuir isotherm. Kinetic of adsorption was perfectly fit by a pseudo-second order dynamic model. The results suggest low-cost corncob biochar prepared by in-house modified pyrolysis could be utilized in wastewater treatment.

Spent coffee grounds are a waste generated in large amounts by the food industry producing instant coffee. While it is used as animal feed, mostly spent coffee grounds are burned. In this study, The spent coffee grounds were modified to be magnetic in order to remove cadmium (II) ion. The magnetic solids are easy to separate from water with a magnet. The biochar was prepared at 400 °C. Several factors that affect the adsorption were studied, such as adsorbent dosage, contact time, initial metal ion concentration and effect of solution pH. At the optimum conditions (the adsorbent dosage 0.1 g l⁻¹, pH 7, time 30 min and the initial concentration 40 mg l⁻¹), the percentage removal of Cd(II) was ∼96%. The surface morphology of the adsorbent showed iron particles with a cubical shape on the adsorbent, with 3–20 μm average diameter. The adsorption data was well fit by a pseudo-second order and a Langmuir isotherm, with the maximum adsorption capacity 10.42 mg/g. The adsorption process was spontaneous and endothermic. The main goal of the study is to re-use the spent coffee grounds waste and use low-cost adsorbent for cadmium (II) removal in aqueous solution. The magnetic biochar was easily manipulated by external magnetic fields after treatment. With good adsorbent performance of the magnetic biochar, spent coffee grounds could be used to treat Cd(II) contamination.

Magnetic biochars were prepared using Fe₃O₄ nanoparticle composites onto the surface of biochar derived from rice husk. The characteristics of magnetic biochar were characterized by scanning electron microscope, x-ray powder diffraction and Fourier-transform infrared techniques. The removal of rhodamine 6G dye by magnetic biochar, compared to pristine biochar was studied. The effects of pyrolysis temperature on rhodamine 6G adsorption was evaluated. Kinetic, isotherms and thermodynamic studies were carried out to investigate the adsorption mechanism of rhodamine 6G dye on magnetic biochar surface. The rhodamine 6G removal efficiency of Fe₃O₄-composited biochar (pyrolyzed at 500 °C) is higher than that of pristine biochar with maximum efficiency of 94% removal. The adsorption isotherm and kinetic studies indicated that the langmuir model, pseudo-first order and pseudo-second order models described well the rhodamine adsorption onto magnetic Fe₃O₄-biochar.

This study investigates the fabrication of a composite film composed of polyvinyl alcohol (PVA) and glycerol, incorporating nanosilica derived from municipal solid waste incinerator bottom ash (BA). The nanosilica is blended with a PVA film-forming solution containing glycerol as a plasticizer. The composite films are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Additionally, thermogravimetric analysis (TGA) is conducted to evaluate the thermal properties, while the mechanical properties are assessed in terms of tensile strength (TS) and elongation at break (EAB). The results indicate that the presence of silica nanoparticles reduces transparency and increases film thickness in the presence of glycerol. Notably, the film containing 1% silica demonstrates a significant enhancement in tensile strength, exhibiting a 50% increase compared to the film without silica. However, higher silica loadings lead to a deterioration in mechanical properties due to silica agglomeration within the polymer matrix. As expected, the presence of silica in the films slightly elevates the degradation temperature.

In order to transform waste tea leaves into a useful/valuable material for removal of Pb²⁺ ions from wastewater, MnFe₂O₄/biochar was synthesized. The tea waste was pyrolyzed at 500 °C to obtain the biochar. Effects of the composition of tea leaves on the physicochemical properties of biochar were evaluated. Biochar and MnFe₂O₄/biochar were mainly organic matter. Regarding inorganic components, aside from Fe and Mn there were considerable albeit small amounts of the mineral elements K and Ca in the MnFe₂O₄/biochar. The MnFe₂O₄/biochar is porous with a specific surface area of 24.38 m² g⁻¹, and the surface is loaded with MnFe₂O₄ and amorphous MnO₂ particles. Also carboxylic acid, hydroxyl, and carbonyl functional groups were formed on the MnFe₂O₄/biochar surfaces. The surface area and pore volume characteristics of the MnFe₂O₄/biochar were also increased compared with the baseline biochar, and the prepared MnFe₂O₄/biochar had mesostructure. The modification of biochar into MnFe₂O₄/biochar improved adsorption of Pb²⁺ ions with the removal increased to ∼98%. The Freundlich isotherm and the pseudo-second order kinetic models matched well Pb²⁺ adsorption onto the MnFe₂O₄/biochar.