Hydroxyapatite (HA) is a material that has been widely applied to replace the damaged bone as a bone implant. Different types of HA have been successfully synthesized by a hydrothermal method based on calcium oxide (CaO) which was originated from chicken eggshells and diammonium hydrogen phosphate (DHP)/(NH₄)₂HPO₄ as their precursors. We present a novel approach to the hydrothermal synthesis of HA form eggshells as a new precursor via a one-step synthesis method. The influence of temperature was also observed to study the effect on the crystallinity, purity, and morphology of obtained HAs. The synthesis was carried out at two different temperatures, 200 °C (HA-200) and 230 °C (HA-230) for 48 h respectively. The structures, purities, and morphologies of hydroxyapatite were analyzed by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR), and Scanning Electron Microscopy- Energy Dispersive Spectroscopy (SEM-EDS), and Transmission electron microscopy (TEM). The XRD patterns show the HA main phase indicated the purity of 96.5% for HA-200 and 99.5% for HA-230. The TEM micrograph suggested a hexagonal-like of HA with an average particle size of 92.61 nm. Hexagonal-like of HAs are suitable for bone implants and further application.

Thermal air oxidation enhances the adsorption capacity of steam-activated carbon coconut shell (SACCS) on MB removal and recovers the adsorption ability of the spent SACCS treated at 350 °C.

Hydroxyapatite (HA) is a well-known calcium phosphate ingredient comparable to human bone tissue. HA has exciting applications in many fields, especially biomedical applications, such as drug delivery, osteogenesis, and dental implants. Unfortunately, hydroxyapatite-based nanomaterials are synthesized by conventional methods using reagents that are not environmentally friendly and are expensive. Therefore, extensive efforts have been made to establish a simple, efficient, and green method to form nano-hydroxyapatite (NHA) biofunctional materials with significant biocompatibility, bioactivity, and mechanical strength. Several types of biowaste have proven to be a source of calcium in forming HA, including using chicken eggshells, fish bones, and beef bones. This systematic literature review discusses the possibility of replacing synthetic chemical reagents, synthetic pathways, and toxic capping agents with a green template to synthesize NHA. This review also shed insight on the simple green manufacture of NHA with controlled shape and size.

The danger from the content of dyes produced by textile-industry waste can cause environmental degradation when not appropriately treated. However, existing waste-treatment methods have not been effective in degrading dyes in textile waste. Zero-valent iron (ZVI), which has been widely used for wastewater treatment, needs to be developed to acquire effective green production. Tea (Camellia sinensis) leaves contain many polyphenolic compounds used as natural reducing agents. Therefore, this study aims to synthesize ZVI using biological reducing agents from tea-leaf extract and apply the Fenton method to degrade the color mixture of rhodamine B and methyl orange. The results show that the highest polyphenols were obtained from tea extract by heating to 90 °C for 80 min. Furthermore, PSA results show that ZVI had a homogeneous size of iron and tea extract at a volume ratio of 1:3. The SEM-EDS results show that all samples had agglomerated particles. The ZVI 1:1 showed the best results, with a 100% decrease in the color intensity of the dye mixture for 60 min of reaction and a degradation percentage of 100% and 66.47% for rhodamine B and methyl orange from LC-MS analysis, respectively. Finally, the decrease in COD value by ZVI was 92.11%, higher than the 47.36% decrease obtained using Fe(II).