The preparation of hydroxyapatite from unrefined calcite residues and its application for lead removal from aqueous solutions

Overview of structure, function and integrated utilization of marine shell

Marine shell resources have received great attention from researchers owing to their unique merits such as high hardness, good toughness, corrosion resistance, high adsorption, and bioactivity. Restricted by the level of comprehensive utilization technology, the utilization rate of shells is extremely low, resulting in serious waste and pollution. The research shows that the unique brick-mud structure of shells makes them have diverse and good functional characteristics, which guides them to have great utilization potential in different fields. Hence, this review highlights the constitutive relationship between microstructure-function-application of shells (e.g., gastropods, cephalopods, and amniotes), and the comprehensive applications and development ideas in the fields of biomedicine, adsorption enrichment, pHotocatalysis, marine carbon sink, and environmental deicer. It is worth mentioning that marine shells are currently well developed in three areas: bone repair, health care and medicinal value, and drug carrier, which together promote the progress of biomedical field. In addition, an in-depth summary of the application of marine shells in the adsorption and purification of various impurities such as crude oil, heavy metal ions and dyes at low-cost and high efficiency is presented. Finally, by integrating thoughts and approaches from different applications, we are committed to providing new pathways for the excavation and future high-value of shell resources, clarifying the existing development stages and bottlenecks, promoting the development of related technology industries, and achieving the synergistic win-win situation of economic and environmental benefits.

Biowaste derived hydroxyapatite embedded on two-dimensional g-C3N4 nanosheets for degradation of hazardous dye and pharmacological drug via Z-scheme charge transfer

In recent years, there has been an increase in demand for inexpensive biowaste-derived photocatalysts for the degradation of hazardous dyes and pharmacological drugs. Here, we developed eggshell derived hydroxyapatite nanoparticles entrenched on two-dimensional g-C3N4 nanosheets. The structural, morphological and photophysical behavior of the materials is confirmed through various analytical techniques. The photocatalytic performance of the highly efficient HAp/gC3N4 photocatalyst is evaluated against methylene blue (MB) and doxycycline drug contaminates under UV-visible light exposure. The HAp/gC3N4 photocatalyst exhibit excellent photocatalytic performance for MB dye (93.69%) and doxycycline drug (83.08%) compared to bare HAp and g-C3N4 nanosheets. The ultimate point to note is that the HAp/gC3N4 photocatalyst was recycled in four consecutive cycles without any degradation performance. Superoxide radicals play an important role in degradation performance, which has been confirmed by scavenger experiments. Therefore, the biowaste-derived HAp combined with gC3N4 nanosheets is a promising photocatalyst for the degradation of hazardous dyes and pharmacological drug wastes.

Recent Progress in the Application of Hydroxyapatite for the Adsorption of Heavy Metals from Water Matrices

Wastewater treatment remains a critical issue globally, despite various technological advancements and breakthroughs. The study of different materials and technologies gained new valences in the last years, in order to obtain cheap and efficient processes, to obtain a cleaner environment for future generations. In this context, the present review paper presents the new achievements in the materials domain with highlights on apatitic materials used for decontamination of water loaded with heavy metals. The main goal of this review is to present the adsorptive removal of heavy metals using hydroxyapatite-based adsorbents, offering a general overview regarding the recent progress in this particular area. Developing the current review, an attempt has been made to give appropriate recognition to the most recent data regarding the synthesis methods and targeted pollutants, including important information regarding the synthesis methods and precursors, morphological characteristics of the adsorbent materials and effectiveness of processes.

The preparation of calcium phosphate adsorbent from natural calcium resource and its application for copper ion removal

Using the hen eggshells (biowaste) as a source of calcium and an environmentally friendly approach, the nanopowder composed of 74% of hydroxyapatite (HA) and 26% of β-tricalcium phosphate (β-TCP) was obtained. Due to the maximum reduction of the stages associated with the use of chemicals and energy, this method can be considered as economically and environmentally friendly. A well-developed surface area and the negative zeta potential at pH above 3.5 indicate good adsorption properties of this material. The obtained material shows high adsorption capacity towards Cu²⁺ ions, i.e. 105.4 mg/g at pH 5. Good fit of the Langmuir adsorption model and the pseudo-second-order kinetic model may indicate chemical adsorption probably due to the electrostatic interactions between the Cu²⁺ cations and the negatively charged phosphate and hydroxyl groups on the material surface.

Removal of Hazardous Contaminants from Water by Natural and Zwitterionic Surfactant-modified Clay

In this study, natural clay (NC) was collected from Saudi Arabia and modified by cocamidopropyl betaine (CAPB) at different conditions (CAPB concentration, reaction time, and reaction temperature). NC and modified clay (CAPB-NC) were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and N2 adsorption at 77 K. The adsorption efficiency of NC and CAPB-NC toward Pb2+ and reactive yellow 160 dye (RY160) was evaluated. The adsorption process was optimized in terms of solution initial pH and adsorbent dosage. Finally, the adsorption kinetics and isotherms were studied. The results indicated that NC consists of agglomerated nonporous particles composed of quartz and kaolinite. CAPB modification reduced the specific surface area and introduced new functional groups by adsorbing on the NC surface. The concentration of CAPB affects the adsorption of RY160 tremendously; the optimum concentration was 2 times the cation exchange capacity of NC. The equilibrium adsorption capacity of CAPB-NC toward RY160 was about 6 times that of NC and was similar for Pb2+. The adsorption process followed the pseudo-second-order kinetics for both adsorptive. RY160 adsorption on CAPB-NC occurs via multilayer formation while Pb2+ adsorption on NC occurs via monolayer formation..

Enhanced extraction of hydroxyapatite from bighead carp (Aristichthys nobilis) scales using deep eutectic solvent

Fish-scale waste is rich in biocompatible hydroxyapatite (HAp). In the present study, an environmentally friendly method of extracting HAp from fish-scale waste was developed in an effort to promote environmental sustainability. Deep eutectic solvents (choline chloride/glycerol, 1/2) were used to extract HAp from bighead carp (Aristichthys nobilis) scales. A relatively high extraction rate of 47.67% ± 1.81% was obtained under optimum conditions (70 °C, a solid/liquid ratio of 1/15 g/g and a 2.5 hr extraction time). The obtained HAp was characterized and its purity was determined using Fourier transform infrared spectroscopy and X-ray diffraction, respectively. The chemical composition was performed by energy-dispersive X-ray spectrometry and inductively coupled plasma-optical emission spectroscopy. Its morphology and particle size were observed using scanning electron microscopy and particle size distribution analysis. Thermogravimetric analysis was used to determine its thermal stability. Blood compatibility was determined using a hemolytic test. The results showed that this extraction yielded HAp with the irregular morphology, the higher Ca/P ratio, good thermal stability, and blood compatibility, indicating that the proposed method is an excellent alternative for the improved utilization of fish scale waste. PRACTICAL APPLICATION: Biocompatible hydroxyapatite (HAp) was extracted from fish scale (FS) waste by using an environmentally friendly deep eutectic solvent. The optimized extraction and structure characterization of extracted HAp were investigated in this study. The results showed that the extracted HAp had the irregular morphology, the higher Ca/P ratio, good thermal stability, and blood compatibility, which indicated that the proposed method was an excellent alternative to improving the utilization of FS waste.