Biowaste-Derived Hydroxyapatite for Effective Removal of Reactive Yellow 4 Dye: Equilibrium, Kinetic, and Thermodynamic Studies

Novel mint-stalks derived biochar for the adsorption of methylene blue dye: Effect of operating parameters, adsorption mechanism, kinetics, isotherms, and thermodynamics

The pyrolysis of mint stalks and lemon peels was performed to synthesize mint-stalks (MBC) and lemon-peels (LBC) derived biochars for adsorbing methylene blue (MB). The preparation, characterization, and application of MBC in adsorption have not been reported in the literature. MBC showed higher surface area and carbon content than that of LBC. The removal ratios of MB were 87.5% and 60% within 90 min for MBC and LBC, respectively at pH 7, temperature of 30oC, adsorbent dose of 0.5 g/L, and MB concentration of 5 mg/L. The optimal MBC dose was 1 g/L achieving a removal efficiency of 93.6% at pH 7, temperature of 30oC, contact time of 90 min, and initial dye concentration of 5.0 mg/L. The adsorption efficiency decreased from 98.6% to 31.33% by raising the dye concentration from 3.0 mg/L to 30 mg/L. Further, the increase of adsorbent dose to 10 g/L could achieve 94.2%, 90.3%, 87.6%, and 84.1% removal efficiencies of MB in the case of initial concentrations of 200 mg/L, 300 mg/L, 400 mg/L, and 500 mg/L, respectively. MBC showed high stability in adsorbing MB under five cycles, and the performed analyses after adsorption reaffirmed the stability of MBC. The adsorption mechanism indicated that the adsorption of MB molecules on the biochar's surface was mainly because of the electrostatic interaction, hydrogen bonding, and π-π stacking. Pseudo-second-order and Langmuir models could efficiently describe the adsorption of MB on the prepared biochar. The adsorption process is endothermic and spontaneous based on the adsorption thermodynamics. The proposed adsorption system is promising and can be implemented on a bigger scale. Moreover, the prepared biochar can be implemented in other applications such as photocatalysis, periodate, and persulfate activation-based advanced oxidation processes.

Photocatalytic degradation of acid yellow 36 with calcined titania-hydroxyapatite-cuo xerogels

Advanced oxidation processes (AOP), using semiconductor (SC) and hydroxyapatite (HA) composites, are promising due to the synergy of photocatalytic and adsorption properties. Still, dye removal efficiency of composites based on HA-SC remains low, because most of the research reported consider single SC materials. In this work, nanocrystalline xerogels of titanium oxide (TiO2) with copper oxide (CuO) and HA were synthesized by the sol-gel process. HA was obtained by the precipitation method without heat treatment and calcined in the range of 200-1000 °C. TiO2 and copper precursors were added to a sol containing HA in a 12:1 mol ratio, obtaining HA-TiO2 and HA-CuO-TiO2 nanomaterials. The xerogels were characterized by X-ray diffraction, scanning electron microscopy, emission field scanning electron microscopy and photoresponse. Their performance in the photocatalytic discoloration of an aqueous solution acid yellow dye 36 (AY36) was evaluated, using visible and UV light. The best discoloration was achieved with HA-CuO-TiO2 xerogels with HA calcined at 600 °C, showing a degradation kinetic constant of 0.24 min-1. In contrast, HA-TiO2 materials showed little or no photocatalytic activity, but strong dye adsorption/desorption. The thermal treatment of HA determines the filament-like morphology and degree of compaction of the nanomaterials, which are relevant in the crystallite size and sensitization of the SC matrix. Further studies must address the surface chemistry and rectifying properties of the best SC composite to have a more complete understanding of the mechanisms involved.

Optimum phosphate ion removal from aqueous solutions using roller kiln industrial solid waste

Water scarcity is the most imperative predicament that concerns the population. In this research, a roller kiln (RK) industrial solid waste was used in the adsorption of phosphate ions from aqueous solutions thus converting a waste to wealth through aiding in serving as a water treatment application. The RK waste was produced from an Egyptian factory with a flow rate of million tons/day. Surface characterization for this solid waste was performed including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infra-red (FTIR), zeta potential (ZP), and particle size distribution (PSD). Based on the kinetics and isotherm studies, the pseudo first order (PFO) kinetic model and Freundlich isotherm model were the best-fitted models with the experimental data as well as the Dubinin-Radushkevich isotherm model indicated that the adsorption type was physical. The attained experimental results were then optimized to attain the experimental conditions at which the optimum adsorption percentage was achieved using response surface methodology (RSM). The optimum percentage removal of phosphate ions 99.5 (%) was achieved at the following experimental conditions; pH 8, temperature = 25 °C, contact time = 9 min, initial phosphate ion concentration = 10 mg/L and adsorbent dose 0.5 = g/L.

Kinetics and Isotherm Studies for Adsorption of Gentian Violet Dye from Aqueous Solutions Using Synthesized Hydroxyapatite

Water is the most important resource for life, but it has been greatly exhausted over the past century as a result of the human population and environmentally harmful activities. The excessive quantity of dyes exists in the wastewater produced from the textile industries which is the main reason for serious human health and environmental problems. There are many dye removal techniques, and the most promising one is the adsorption technique. The novelty of this research is using unmodified synthesized hydroxyapatite (HAp) as an adsorbent for the removal of gentian violet (GV) dye from aqueous solutions as there are no sufficient data in the literature about using it in the adsorption of GV dye from aqueous solutions. Unmodified HAp was synthesized by a combined precipitation microwave method. The prepared adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analyses. The kinetic study showed that the pseudo-second-order (PSO) model was the best fitted model with the experimental data. Analysis of adsorption isotherms using different models showed that this adsorption system was better described by the Halsey isotherm with a maximum adsorption capacity (q_max)  of 1.035 mg/g. The effects of experimental factors such as initial solution pH, initial dye concentration, adsorbent dose, and contact time were studied during the investigation of GV dye removal efficiency. The experimental results indicated that the maximum adsorption efficiency (99.32%) of the GV dye using HAp adsorbent was achieved at the following conditions: contact time = 90 min, pH = 12, initial GV dye concentration = 3 mg/L, and adsorbent dose = 1 g/L. The adsorption mechanism of the GV dye using HAp might be explained by the electrostatic interaction between the negatively charged surface of the HAp and the positively charged group of the GV dye. Thermodynamics study was performed on the adsorption process of GV dye from aqueous solutions using the synthesized HAp which revealed that this process was endothermic and spontaneous due to positive values of ΔH and ΔS and negative values of ΔG.

Removal of Dye from Wastewater Using a Novel Composite Film Incorporating Nanocellulose

Research shows that the composite material is used as an adsorbent to remove pollutants from wastewater. This work is aimed at producing a novel composite film comprising chitosan, polyvinyl alcohol, and cornstarch incorporating nanocellulose (CPCN). The composite film was prepared by a blending method wherein nanocellulose was extracted using a chemical method from banana bract. The prepared CPCN was characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) with EDX to understand their molecular interaction and surface morphology, respectively. The effect of parameters including pH, adsorbent dosage, initial dye concentration, and contact time on the adsorption of methylene blue (MB) dye was studied. The maximum adsorption was found to be up to 63.13 mg/g MB with a pH of 10, adsorbent dosage of 2 g, an initial concentration of 150 ppm, and contact time of 120 min at room temperature (25°C) indicating a moderate adsorption capacity of the CPCN. Comparing the Langmuir and Freundlich adsorption isotherm models, the former fitted well with MB dye adsorption data, implying that the models can be applied to uptake MB dye by CPCN. In the kinetic adsorption experiment, the adsorbed dye almost reached equilibrium at about 120 min for the CPCN and followed the pseudo-second-order kinetic model. Therefore, the CPCN can be used as a potential adsorbent in wastewater treatment.

Synthesis of hydroxyapatite nanoparticles using Acacia falcata leaf extract and study of their anti-cancerous activity against cancerous mammalian cell lines

This study deals with the synthesis of hydroxyapatite nanoparticles (HAPnps) mediated by Acacia falcata leaf extract. Aggregates of needle-shaped crystalline nanostructures were confirmed by FE-SEM and TEM analysis. Well-defined rings in the SAED patterns corroborated the polycrystalline nature of the HAPnps. Individual elements present in the HAPnps were attested by the specific signals for Ca, P, and O in the EDS and XPS analyses. The distinct peaks observed in the XRD spectrum matched well with the HAP hexagonal patterns with a mean crystallite size of 55.04 nm. The FTIR study unveiled the coating of the nanoparticles with the biomolecules from Acacia falcata leaves. The suspension HAPnps exhibited polydispersity (0.446) and remarkable stability (zeta potential: - 31.9 mV) as evident from DLS studies. The pore diameter was 25.7 nm as obtained from BET analysis, suggesting their mesoporous nature. The HAPnps showed the cytotoxic effect on A549 lung and MDA-MB231 breast carcinoma cell lines, with an IC₅₀ value of 55 μg/mL. The distortion of the cell membrane and cell morphology, along with the chromatin condensation and cell necrosis on treatment with HAPnps were detected under fluorescence microscopy post acridine orange/ethidium bromide dye staining. This study reports the anti-cancerous potential of non-drug-loaded plant-mediated HAPnps. Therefore, the HAPnps obtained in this investigation could play a vital role in the biomedical field of cancer therapy.

From waste to waste: iron blast furnace slag for heavy metal ions removal from aqueous system

Inordinate levels of heavy metals in water sources have long been a matter of concern, posing serious environmental and public health risks. Adsorption, on the other hand, is a viable technique for removing heavy metals from water due to its high efficiency, low cost, and ease of operation. Blast furnace slag (BFS) is considered a cheap sorbent for the get rid of Co²⁺ and Pb²⁺ ions from aqueous media. The nonmodified slag is characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), N₂ adsorption-desorption isotherms, energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and zeta potential. The removal of Co²⁺ and Pb²⁺ ions was carried out using batch adsorption experiments from an aqueous medium. The influence of several variables as pH, contact time, adsorbent dose, temperature, and initial ions concentration was considered. The isotherm, kinetic, thermodynamic, and recyclability were also conducted. The maximum uptake capacity for Co²⁺ and Pb²⁺ was 43.8 and 30.2 mg g^-1 achieved at pH 6 after 60 min contact time. The adsorption kinetics and isotherms of BFS for Co²⁺ and Pb²⁺ fitted well to Avrami and Freundlich models, respectively. The main adsorption mechanism between BFS and the metal ions was ion exchange. The regeneration of the used slag was studied for reuse many cycles. In terms of economics and scalability, nonmodified BFS treatment has great potential as a cost-effective adsorbent that could be used in water pollution treatment.

Adsorptive removal of Acid Blue 113 using hydroxyapatite nanoadsorbents synthesized using Peltophorum pterocarpum pod extract

The present work reports the study on the green synthesis of hydroxyapatite (HAP) nanoadsorbents using Peltophorum pterocarpum pod extract. HAP nanoadsorbents were characterized by using FESEM, EDS, TEM, XRD, FTIR, XPS, and BET analyses. The results highlighted the high purity, needle-like aggregations, and crystalline nature of the prepared HAP nanoadsorbents. The surface area was determined as 40.04 m²/g possessing mesopores that can be related to the high adsorption efficiency of the HAP for the removal of a toxic dye, - Acid Blue 113 (AB 113) from water. Central Composite Design (CCD) was used for optimizing the adsorption process, which yielded 94.59% removal efficiency at the optimum conditions (dose: 0.5 g/L, AB 113 dye concentration: 25 ppm, agitation speed: 173 rpm, and adsorption time: 120 min). The adsorption kinetics followed the pseudo-second-order model (R²:0.9996) and the equilibrium data fitted well with the Freundlich isotherm (R²:0.9924). The thermodynamic parameters indicated that the adsorption of AB 113 was a spontaneous and exothermic process. The highest adsorption capacity was determined as 153.85 mg/g, which suggested the promising role of green HAP nanoadsorbents in environmental remediation applications.

Recycling phosphorus and calcium from aquaculture waste as a precursor for hydroxyapatite (HAp) production: a review

Water contaminated with phosphorus needs to be managed efficiently to ensure that clean water sources will be preserved. Aquaculture plays an essential role in supplying food and generating high revenue. However, the quantity of phosphorus released from aquaculture effluents is among the major concerns for the environment. Phosphorus is a non-renewable, spatially concentrated material essential for global food production. Phosphorus is also known as a primary source of eutrophication. Hence, phosphorus recovery and separation from different wastewater streams are mandatory. This paper reviews the source of phosphorus in the environment, focusing on aquaculture wastewater as a precursor for hydroxyapatite formation evaluates the research progress on maximizing phosphorus removal from aquaculture wastewater effluents and converting it into a conversion. Shrimp shell waste appears to be an essential resource for manufacturing high-value chemicals, given current trends in wealth creation from waste. Shrimp shell waste is the richest source of calcium carbonate and has been used to produce hydroxyapatite after proper treatment is reviewed. There have been significant attempts to create safe and long-term solutions for the disposal of shrimp shell debris. Through the discussion, the optimum condition of the method, the source of phosphorus, and the calcium are the factors that influence the formation of hydroxyapatite as a pioneer in zero-waste management for sustainability and profitable approach. This review will provide comprehensive documentation on resource utilization and product development from aquaculture wastewater and waste to achieve a zero-waste approach.

Characterization of the Physical, Chemical, and Adsorption Properties of Coal-Fly-Ash–Hydroxyapatite Composites

(1) Hydroxyapatite (HAp), which can be obtained by several methods, is known to be a good adsorbent. Coal fly ash (CFA) is a commonly reused byproduct also used in environmental applications as an adsorbent. We sought to answer the following question: Can CFA be included in the method of HAp wet synthesis to produce a composite capable of adsorbing both heavy metals and dyes? (2) High calcium lignite CFA from the thermal power plant in Bełchatów (Poland) was used as the base to prepare CFA–HAp composites. Four types designated CFA–HAp1–4 were synthesized via the wet method of in situ precipitation. The synthesis conditions differed in terms of the calcium reactants used, pH, and temperature. We also investigated the equilibrium adsorption of Cu(II) and rhodamine B (RB) on CFA–HAp1–4. The data were fitted using the Langmuir, Freundlich, and Redlich–Peterson models and validated using R2 and χ2/DoF. Surface changes in CFA–HAp2 following Cu(II) and RB adsorption were assessed using SEM, SE, and FT-IR analysis. (3) The obtained composites contained hydroxyapatite (Ca/P 1.67) and aluminosilicates. The mode of Cu(II) and RB adsorption could be explained by the Redlich–Peterson model. The CFA–HAp2 obtained using CFA, Ca(NO3)2, and (NH4)2HPO4 at RT and pH 11 exhibited the highest maximal adsorption capacity: 73.6 mg Cu/g and 87.0 mg RB/g. (4) The clear advantage of chemisorption over physisorption was indicated by the Cu(II)–CFA–HAp system. The RB molecules present in the form of uncharged lactone were favorably adsorbed even on strongly deprotonated CFA–HAp surfaces.

Structure-Activity Relationship of Lanthanide-Incorporated Nano-Hydroxyapatite for the Adsorption of Fluoride and Lead

The growing demand for water purification provided the initial momentum to produce lanthanide-incorporated nano-hydroxyapatite (HAP) such as HAP·CeO2, HAP·CeO2·La(OH)3 (2:1), and HAP·CeO2·La(OH)3 (3:2). These materials open avenues to remove fluoride and lead ions from contaminated water bodies effectively. Composites of HAP containing CeO2 and La(OH)3 were prepared using in situ wet precipitation of HAP, followed by the addition of Ce(SO4)2 and La(NO3)3 into the same reaction mixture. The resultant solids were tested for the removal of fluoride and lead ions from contaminated water. It was found that the composite HAP·CeO2 shows fluoride and lead ion removal capacities of 185 and 416 mg/g, respectively. The fluoride removal capacity of the composite was improved when La(OH)3 was incorporated and it was observed that the composite HAP·CeO2·La(OH)3 (3:2) has the highest recorded fluoride removal capacity of 625 mg/g. The materials were characterized using scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) spectrometry, Fourier transform infrared (FT-IR) spectrometry, X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area analysis. Analysis of results showed that Ce and La are incorporated in the HAP matrix. Results of kinetic and leaching analyses indicated a chemisorptive behavior during fluoride and lead ion adsorption by the composites; meanwhile, the thermodynamic profile shows a high degree of feasibility for fluoride and lead adsorption.

Methylene Blue Dye Adsorption from Wastewater Using Hydroxyapatite/Gold Nanocomposite: Kinetic and Thermodynamics Studies

The present work demonstrates the development of hydroxyapatite (HA)/gold (Au) nanocomposites to increase the adsorption of methylene blue (MB) dye from the wastewater. HA nanopowder was prepared via a wet chemical precipitation method by means of Ca(OH)₂ and H₃PO₄ as starting materials. The biosynthesis of gold nanoparticles (AuNPs) has been reported for the first time by using the plant extract of Acrocarpus fraxinifolius. Finally, the as-prepared HA nanopowder was mixed with an optimized AuNPs solution to produce HA/Au nanocomposite. The prepared HA/Au nanocomposite was studied by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) analysis. Adsorption studies were executed by batch experiments on the synthesized composite. The effect of the amount of adsorbent, pH, dye concentration and temperature was studied. Pseudo-first-order and pseudo-second-order models were used to fit the kinetic data and the kinetic modeling results reflected that the experimental data is perfectly matched with the pseudo-first-order kinetic model. The dye adsorbed waste materials have also been investigated against Pseudomonas aeruginosa, Micrococcus luteus, and Staphylococcus aureus bacteria by the agar well diffusion method. The inhibition zones of dye adsorbed samples are more or less the same as compared to as-prepared samples. The results so obtained indicates the suitability of the synthesized sample to be exploited as an adsorbent for effective treatment of MB dye from wastewater and dye adsorbed waste as an effective antibacterial agent from an economic point of view.

Hydroxyapatite with magnetic core: Synthesis methods, properties, adsorption and medical applications

This review presents the actual state of knowledge and recent research results on the magnetic composite synthesized from iron oxide (γ-Fe₂O₃ or Fe₃O₄) and hydroxyapatite. It can be obtained applying some methods, i.e. chemical precipitation, hydrothermal, sol-gel, and biomimetic or combined techniques which exhibit characteristic properties affecting the form of the prepared product. More specific details are discussed in this paper. A comparison of the discussed synthesis methods is presented. On the basis of selected publications, a comparison of the results of the analysis by XRD, FTIR, SEM and EDX methods for hydroxyapatite with a magnetic core was also presented. Moreover, the characteristics large adsorption capacity and specific area allow employing nanocomposites as adsorbents particularly in removal of toxic metal ions. Nowadays this issue is extremely vital due to large amounts of pollutants in the environment and greater ecological awareness of people. Moreover, magnetic hydroxyapatite can be also applied as a catalyst in various syntheses or oxidation reactions as well as in medicine in magnetic resonance imaging, hyperthermia treatment, drug delivery and release, bone regeneration or cell therapy.

Spectral characterization of hydroxyapatite extracted from Black Sumatra and Fighting cock bone samples: A comparative analysis

At present, chicken business is occupying a major portion in the market and huge amount of bone wastes are dumped into the open places lead in environmental pollution. In this analysis, natural hydroxyapatite was extracted by thermal calcination process at different temperature ranges from 700 °C, 900 °C and 1100 °C and compared its spectral characteristics. The crystalline nature, functional groups and morphological characteristics of hydroxyapatite obtained from both bone samples were studied using XRD, FTIR and SEM analysis. The crystallite size, lattice parameters, specific surface area, volume and degree of crystallinity were measured using XRD data. The mean grain size of Black Sumatra and Fighting Cock bone hydroxyapatite was 62.67 nm and 31.34 nm respectively. The FTIR spectrum showed major peaks at 634.58 cm⁻¹ and 470.63 cm⁻¹, 1413.82 cm⁻¹ and 1460 cm⁻¹ indicates the presence of carbonate group and phosphate groups in both samples. The SEM micrograph confirmed the existence of maximum pores in matrix of fighting cock bone than Black Sumatra bone sample. Thus, the comparative analysis concluded that nano-sized hydroxyapetite obtained from bone wastes of fighting cock can be utilized as a low-cost biomaterial for the production of various implant coating materials and substitute for ceramics in bones and dentistry applications.

Nanohydroxyapatite-, Gelatin-, and Acrylic Acid-Based Novel Dental Restorative Material

The aim of this study was to prepare a novel dental restorative material (NDRM) and to understand its cell viability behavior. The hydroxyapatite (HA) nanopowder was synthesized using a wet chemical precipitation method using calcium hydroxide and orthophosphoric acid as precursors. The as-prepared HA nanopowder was annealed at different temperatures to get a pure compound with a Ca/P ratio close to 1.67. The optimal temperature was found to be 600 °C, whereas at a higher temperature, HA starts decomposing into CaO. The preparation of NDRM was conducted in two steps. The first step comprises the preparation of HA nanopowder- and gelatin (G)-based film using microwave heating. In the second step, the homogenized mixture of the HA-G film was mixed with different amounts of acrylic acid to form a self-flowable NDRM paste. Further, both these materials (HA nanopowder and NDRM) were characterized using FTIR, XRD, and SEM-EDX analyses. The FTIR and XRD results show the peaks corresponding to natural bone apatite and therefore confirm the formation of HA. EDX results showed the presence of Ca and P in HA nanopowder and NDRM with Ca/P ratios of 1.79 and 1.63, respectively. Synthesized NDRM was also analyzed for its in vitro cytotoxic and reproductive viability potential against normal cells using MTT and clonogenic assay. The analysis showed significantly higher cellular viability on the treatment with NDRM when compared to HA nanopowder as well as no colony suppression by both materials was observed on the normal cell line (fR2) even after exposure for 24 h, indicating its nontoxicity. The synthesized NDRM therefore can be considered as a promising candidate for dental caries restoration applications.

Simultaneous removals of cadmium(II) ions and reactive yellow 4 dye from aqueous solution by bone meal-derived apatite: kinetics, equilibrium and thermodynamic evaluations

The simultaneous removal of Cadmium ions and reactive yellow 4 dye (RY4 dye) by bone meal-derived apatite (BMDA) were investigated in a batch process. The structural elucidation of the prepared BMDA was done using TEM, XRD, FT-IR and EDX to evaluate the structures of the adsorbent. Different experimental features such as the agitation time, BMDA dosage, temperature, initial adsorbate concentration and pH of the solution were examined on the uptake pattern of the pollutants. The mechanism of adsorption was examined with Elovich, pseudo-first-order, intraparticle diffusion and pseudo-second-order kinetic models, while Langmuir, Dubinin-Radushkevich (D-R), Freundlich and Tempkin isotherms were exploited in order to describe the behaviour of the equilibrium process. Analysis from XRD revealed peaks corresponding to single phase apatite powder, while the various forces responsible for the interactions between the BMDA surface and the pollutants were obtained to CO32−, OH− and PO43− as observed by FT-IR analysis. SEM and TEM investigations confirmed a round-like morphology which agglomerated together upon the adsorption of pollutants.

The kinetic modelling of the adsorption data were well illustrated with the pseudo-first-order model with correlation coefficient (R2) values ranging from 0.997 to 0.999. Isotherms studies revealed that best fit was achieved with Langmuir isotherm with adsorption capacities of 94.85 and 116.16 mg/g for RY4 dye and Cd(II) ions respectively. Thermodynamic study signified the uptake of the pollutants to be spontaneous, feasible and endothermic in nature. The values of entropy change (ΔS) for the sorption processes calculated are 86.57 and 60.16 J/mol/K for Cd(II) and RY4 dye, respectively.

Hydroxyapatite, a multifunctional material for air, water and soil pollution control: A review

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), a calcium phosphate biomaterial, is a very promising candidate for the treatment of air, water and soil pollution. Indeed, hydroxyapatite (Hap) can be extremely useful in the field of environmental management, due in one part to its particular structure and attractive properties, such as its great adsorption capacities, its acid-base adjustability, its ion-exchange capability and its good thermal stability. Moreover, Hap is able to constitute a valuable resource recovery route. The first part of this review will be dedicated towards presenting Hap's structure and defining properties that result in its viability as an environmental remediation material. The second will focus on its use as adsorbent for wastewater and soil treatment, while indicating the mechanisms involved in this remediation process. Finally, the last part will impart all findings on Hap's applications in the field of catalysis, whether it be as catalyst, as photocatalyst, or as active phase support. Hence, all of the above will have served in showcasing the benefits gained by employing hydroxyapatite in air, water and soil clean-up.

Biocompatible chitosan-collagen-hydroxyapatite nanofibers coated with platelet-rich plasma for regenerative engineering of the rotator cuff of the shoulder

Over the last few decades, extraordinary progress has been accomplished in the field of bone tissue engineering. Containing an incredible number of growth factors required for the process of osteogenesis, platelet-rich plasma (PRP) has gained much interest. However, because of the conflicting results obtained in various investigations, its adequacy remains a riddle. Accordingly, in this paper, we explore the in vitro application of biocompatible chitosan–collagen–hydroxyapatite (CS–COLL–HAP) nanofibers coated with platelet-rich plasma (PRP) (CS–COLL–HAP/PRP) scaffolds for the regenerative engineering of the rotator cuff (RCF) of the shoulder. FTIR spectroscopy, XRD, SEM-EDX and HRTEM were performed to evaluate the characteristics of nanofibers. After confirmation of the physicochemical properties of nanofibers, the osteogenic capability of the scaffold was assessed by measuring the relative calcium content, ALP activity, and gene expression. The results of viability and live/dead assay and cell adhesion test indicated the adequacy of the PRP when coupled with nanofibers in contrast to the other tested groups. In vivo staining affirmed increased collagen association in the PRP with nanofiber scaffolds at 30 days and 60 days. In conclusion, the addition of the PRP into CS–COLL–HAP nanofibers in this examination affected the osteogenic differentiation of osteoblast cells, and therefore, it may have an incredible perspective for bone tissue applications.

Over the last few decades, extraordinary progress has been accomplished in the field of bone tissue engineering.