Hydroxyapatite Adsorbent Research Articles

Study on the performance and mechanism of cobaltous ion removal from water by a high-efficiency strontium-doped hydroxyapatite adsorbent.

In this study, a high-efficiency strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol-gel method for removing cobaltous ions (Co(II)) from water. The effects of adsorbent dose, initial solution pH, initial Co(II) concentration and temperature on the removal performance of Co(II) were investigated. Experimental results indicated that the optimum Sr-HAP dose was 0.30g/50mL solution, the Sr-HAP adsorbent could effectively remove Co(II) in a wide pH range of 3-8. Increasing temperature was conducive to the adsorption, and the maximum Co(II) adsorption capacity by Sr-HAP reached 48.467mg/g at 45°C. The adsorption of Co(II) followed the pseudo-second-order kinetic model, indicating that the Co(II) adsorption by Sr-HAP was attributed mainly to chemisorption. The isothermal adsorption results showed that at lower Co(II) equilibrium concentration, the Langmuir model fitted the data better than the Freundlich model but opposite at higher Co(II) equilibrium concentration. Therefore, the adsorption of Co(II) was a process from monolayer adsorption to multilayer adsorption with the increase of the Co(II) equilibrium concentration. The diffusion analysis of Co(II) to Sr-HAP indicated that the internal diffusion and surface adsorption were the rate-controlled steps of Co(II) adsorption. Thermodynamic study demonstrated that the Co(II) adsorption process was spontaneous and endothermic. The mechanism study revealed that in addition to chemisorption, Sr-HAP also removed Co(II) ions from water via ion exchange and surface complexation.

Porous metakaolin geopolymer as a reactive binder for hydroxyapatite adsorbent granules in dye removal

In this study, porous hydroxyapatite-metakaolin geopolymer (HAP-MK-GP) granules were prepared with a novel method for adsorption of organic pollutants from aqueous solutions, using brilliant green dye as a model compound. The preparation involved combining finely powdered hydroxyapatite, metakaolin, and solid sodium metasilicate in a high-shear granulator. Then, hydrogen peroxide (H2O2) was added at different concentrations (0.0, 5.0, 7.5, or 10.0%) as a combined granulation fluid and blowing agent. In the resulting granules, metakaolin geopolymer bound the powdered hydroxyapatite as granules and contributed to the adsorption capacity. To determine their structural, morphological, and mechanical properties, the granules were characterized with infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, specific surface area and porosity analysis, and compressive strength tests. The granules had a high porosity and promising compressive strength and Young's modulus of 0.8 and 10 MPa, respectively, potentially enabling their use in large-scale adsorption columns. The monolayer adsorption mechanism of brilliant green dye onto HAP-MK-GP granules was confirmed by fitting the obtained batch adsorption data to the Langmuir isotherm model which showed that the adsorption capacity was approximately 41 mg/g. The optimum conditions were: pH of 7, initial dye concentration of 100 mg/L, adsorbent dose of 3 g/L, agitation speed of 250 rpm, contact time of 30 min, and temperature of 298 K. The adsorption kinetic data indicated that the adsorption followed the pseudo-second-order kinetic model. The thermodynamic parameters, including Gibbs free energy, enthalpy, entropy, and activation energy, indicated that adsorption was spontaneous, endothermic, and was based on physisorption. The rate-limiting step was film diffusion. Based on the results, HAP-MK-GP granules could be a feasible adsorbent for the removal of dyes from industrial wastewater. Moreover, the facile granulation method presented here could be applied to other powdered adsorbents as well to prepare adsorbent granules.

Stearic acid-modified hollow hydroxyapatite particles with enhanced hydrophobicity for oil adsorption from oil spills

Oil spills lead to a substantial depletion of aquatic biodiversity. The mitigation of an oil spill can entail considerable financial outlays, give rise to consequential environmental impacts, and present formidable operational complexities. In this research, hollow hydroxyapatite particles with enhanced oil adsorption characteristics were prepared by surface modification with stearic acid. Peanut and vacuum pump oils were used to imitate oil spills and conduct adsorption tests. The 50% stearic acid-modified hydroxyapatite (Sa/HAP) adsorbent showed superior hydrophobic properties with respect to water contact angle data. Adsorption isotherm analysis revealed that the adsorption processes of peanut and vacuum pump oils matched well with the Sips isotherm model, with regression coefficients of 0.992 and 0.996, respectively. The oil adsorption by the modified hydroxyapatite (HAP) adsorbent was found to be 9.85 g·g−1 for peanut oil and 12.13 g·g−1 for vacuum pump oil. Furthermore, the adsorption kinetics performance was determined by chemical interaction, whereas the adsorption equilibrium capacities were 8.97 g·g−1 and 11.41 g·g−1, respectively. Recycling of the spent adsorbent was performed with toluene stripping. The synthesized oil-adsorbents were analyzed by SEM, FTIR, XRD, contact angle, and TGA analyses. Hence, the efficacy of the Sa/HAP material as a potential adsorbent for the purification of oil-contaminated water was established, attributed to its commendable oil adsorption capability.

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 (qmax) 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.

Strontium-doped hydroxyapatite as an efficient adsorbent for Cd(II) removal from wastewater: Performance, kinetics, and mechanism

A strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol–gel method and used to remove Cd(II) from wastewater. The adsorption performance of the as-prepared Sr-HAP and the kinetics and mechanism of Cd(II) removal were investigated. The experimental results showed that the Sr-HAP adsorbent achieved the maximum Cd(II) adsorption capacity (158.30 mg/g) at a temperature of 298 K, an adsorbent dosage of 0.08 g/50 mL, and an initial solution pH of 6. The adsorption of Cd(II) onto the Sr-HAP adsorbent was well described by the Langmuir isothermal adsorption model and pseudo-second-order kinetic model, and was found to follow a monolayer chemisorption process. In addition, the internal diffusion model was also used to fit the experimental data. The results indicated that the Cd(II) adsorption process was controlled by both internal diffusion and surface adsorption. Thermodynamic analysis revealed that the Cd(II) adsorption process was a spontaneous endothermic process. Moreover, acidic reagents favored the desorption of Cd(II) from the Sr-HAP adsorbent, and the recycled Sr-HAP adsorbent still maintained a high adsorption capacity for Cd(II). Mechanism analysis revealed that the removal process of Cd(II) ions by the Sr-HAP adsorbent possibly involved ion exchange, co-precipitation, and surface complexation. Overall, the synthesized Sr-HAP exhibited an excellent adsorption capacity and good stability, thus acting as a promising candidate for removing Cd(II) from wastewater. • An efficient strontium-doped hydroxyapatite was synthesized for Cd(II) removal. • The Sr-HAP adsorbent had a high Cd(II) adsorption capacity. • The adsorption of Cd(II) by Sr-HAP was proved to be a monolayer chemiadsorption process. • The Sr-HAP adsorbent could maintain its high adsorption ability after regeneration. • The mechanism of Cd(II) uptake by Sr-HAP was comprehensively elucidated.

Development of a New Dolomite-Based Adsorbent with Phosphorus and the Adsorption Characteristics of Arsenic (III) in an Aqueous Solution

In recent decades, the removal of hazardous chemicals that have entered wastewater and groundwater as a result of industrial and consumer activities has become an issue of concern. Specifically, removing arsenic (III) from groundwater is critical and equally crucial in the use of low-cost, efficient adsorbent materials. One purpose of this study was to develop a low-cost hydroxyapatite adsorbent (Ca5(PO4)3OH) by reacting the Ca component of calcined dolomite with phosphorus, and another was to apply the developed adsorbent to remove arsenic (III) from well water in developing countries. In this study, phosphorus adsorption was performed on thermally calcined dolomite, and the adsorption isotherm of the phosphorus study was investigated on selected calcined dolomite. The maximum amount of phosphorus on the selected calcined dolomite was 194.03 mg-P/g, and the Langmuir isotherm model was fitted. Arsenic (III) adsorption was investigated in a wide pH range (pH 2~12) using the new adsorbent. The amount of arsenic (III) adsorbed was 4.3 mg/g. The new absorbent could be effective in removing arsenic (III) and become an affordable material.

Effect of Hydroxyapatite (HAp) Adsorbent Dosage towards Lead Removal

Effect of Hydroxyapatite (HAp) Adsorbent Dosage towards Lead Removal

Purification Behavior of Zn(II) in Water by Magnesium Hydroxyapatite: Surface Complexation, and Dissolution-Precipitation.

As an innovative and economical material, hydroxyapatite does little harm to the environment. In this study, a magnesium hydroxyapatite (Mg-HAP) adsorbent was prepared by doping magnesium. Magnesium doping can increase the hydroxyl groups on the surface of Mg-HAP to form more adsorption sites and improve the removal effect of the heavy metal Zn(II) in water. This study was implemented to survey the effect of different sorption elements, including the liquor initial pH, initial concentration, dose of adsorbents, and other factors, on the adsorption effect. The outcomes show that the sorption effect was best at the time that the liquor was weakly acidic (pH = 6); At a pH of 6, the temperature of 25 °C when the optimal dosage of adsorbent is 0.25 g, the maximum adsorption amount is 62.11 mg/g. Through data fitting, the adsorption process can be accurately described as a pseudo-second-order dynamics model and the Langmuir isotherm equation. According to the thermodynamic analysis, the sorption of zinc ions by Mg-HAP belongs to the process of spontaneous endothermic and entropy increase, and the increase of temperature was conducive to adsorption. Material characterization and analysis indicate that surface complexation and dissolution-precipitation was the main mechanism for adsorption of Zn(II).

Mechanical properties of the hydroxyapatite and magnetic nanocomposite of hydroxyapatite adsorbents

In the current study, a special technique was used to prepare hydroxyapatite (HAp) and magnetic nano composite of hydroxyapatite (HAp/Fe3O4). In order to investigate the mechanical properties of the produced materials, Vickers hardness method and direct crack measurements method were used, The three point bending test was also applied to determine the bending strength. The maximum hardness under 98 N force was determined to be 750 MPa for the magnetic nanocomposite of hydroxyapatite. The crack size of the adsorbents were measured by SEM technique and the maximum KIC was reported 0.65 MPa.m1/2 for the magnetic hydroxyapatite adsorbent. Besides, the bending strength for HAp/Fe3O4 was 3.9 Mpa which was higher than the pure hydroxyapatite. It has been found that Fe3O4 nano particles can improve the mechanical properties of the hydroxyapatite adsorbent significantly.

New insights on physico-chemical investigation of bisphosphonate adsorption isotherm into apatite substrate using statistical physics treatment

In this paper, a well-crystallized hydroxyapatite (HA) and nanocrystalline apatites (NCA) were used to interpret the adsorption process of two bisphosphonates (BPs), namely Tiludronate (Tilu) and Risedronate (Rise). These BPs are among the most prescribed classes of drugs for the treatment of bone disorders disease, particularly Osteoporosis. The equilibrium data used to express the variation of uptake capacity as a function of concentration were determined by varying some experimental physicochemical conditions (e.g. temperature and pH). A preliminary analysis of all the adsorption isotherms obviously indicates that the adsorption quantity tends towards a saturation level. This suggests a finite number of adsorbed layers involved in the adsorption mechanisms. To give a reasonable analysis of the drug adsorption process, three advanced models are proposed and developed in the light of a statistical physics treatment which is tested and discussed. The modeling analysis reveals that the adsorption of the two drugs occurs by the formation of two different adsorbed layers on the apatite surface. Based on the analysis of the selected model parameters, it was deduced that both drugs molecules were anchored alternately with parallel and non-parallel positions on the apatite substrate. The study of the uptake capacities at saturation showed that these parameters followed the sequence: Qasat (Rise-NCA) ˃ Qasat (Rise-HA) ˃ Qasat (Tilu-HA), indicating that the NCA adsorbent was more effective for the Rise drug adsorption than the HA adsorbent. The estimated adsorption energies globally varied from 9.20 to 19.52 kJ/mol, confirming the physical nature of the adsorption process for the investigated systems. Conventionally, to characterize the adsorption process, the entropy (Sa), the enthalpy of Gibbs (G) and the internal energy (Eint) were treated and interpreted.

Synthesis of a novel magnetic zeolite–hydroxyapatite adsorbent via microwave-assisted method for protein adsorption via magnetic solid-phase extraction

Proteins have a critical role in life, and their separation and detection are of high importance. In the present study, magnetic hydroxyapatite was reinforced with zeolite to become a novel adsorbent synthesized by microwave-assisted method to separate protein via magnetic solid-phase extraction. The synthesized procedure was optimized through the mass ratio of zeolite to hydroxyapatite and radiation time. The synthesized nanocomposite was characterized by techniques such as XRD, EDAX, FESEM, TEM, FTIR, VSM, and BET. Structural evaluation reveals that the magnetic zeolite as a core provides a bed for HAP spherical crystals formation and HAP crystals dispersed over the magnetic zeolites or as large grains located around it. The experimental data revealed the maximum separation was achieved at contact time 60 min, initial pH 2, protein concentration 1.2 mg/mL, and adsorbent dosage 50 mg without any salt in the solution. The maximum adsorption capacity was 82.62 mg/g. Desorption efficiency of 95% at initial pH 12 and separation efficiency more than 50% after 4 successive regeneration cycles are the advantages of the adsorbent. The adsorption studies showed that Freundlich and pseudo-second-order models were well fitted with the obtained experimental data.

Azo dye adsorption on an industrial waste-transformed hydroxyapatite adsorbent: Kinetics, isotherms, mechanism and regeneration studies

Nanocrystalline hydroxyapatite (HAp) with high surface area was synthesized by surfactant-assistant hydrothermal method from an industrial waste phosphogypsum. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen sorption characterizations revealed that HAp crystals grow as needle-like particles along the c direction with surface area of 86 and 135 m2/g for the samples synthesized without and with Brij-93 surfactant, respectively. Adsorption of anionic azo dye Congo Red (CR) were conducted on both samples, taking into account the influence of initial dye concentration (100–500 mg/L), adsorbent dosage (0.5–30 g/L), contact time (5–180 min) and solution pH (2–12). Kinetic studies showed that the adsorption of CR followed pseudo-second-order model, i.e., chemisorption is the rate controlling step. Freundlich isotherm was found to be most suitable model for the adsorption of CR, i.e. adsorption is multilayer process. The calculated maximum adsorption capacity of synthesized B93-HAp adsorbent using Brij-93 surfactant was found to be 139 mg/g at pH 5.5 and dosage of 2 g/L. Two predominant mechanisms were observed for CR adsorption, electrostatic attraction and hydrogen bonding as revealed by Fourier transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) studies. The multi-cycle sorption/desorption tests indicated that waste-transformed adsorbent could be regenerated and reused up to 6 cycles. Therefore, this work shows that the conversion of waste materials into adsorbents has a two-fold environmental benefit for both waste management and wastewater treatment.

A Review on Lead Sources, Occurrences, Health Effects, and Treatment Using Hydroxyapatite (HAp) Adsorbent Made from Fish Waste

The issues of heavy metal contamination in water sources have been increasing substantially along with the rapid pace of industrial revolution. Lead, particularly, is one of the heavy metals that received considerable attention lately due to its frequent detection in the environment and hazardous effects. Although conventional water treatment processes had been utilized for ages, it is still a challenge to remove lead in the treatment plant effectively. In line with the advancement of chemistry and nanotechnology, the study on hydroxyapatite (HAp) nanopowder made from fish waste (skin, bones, and scales) has brought to its beneficial use as an adsorbent for lead removal in water. This paper reviews on the sources, occurrences, and health effects of lead as well as the treatment of lead using HAp adsorbent for its removal in water.

Preparation of anionic-cationic co-substituted hydroxyapatite for heavy metal removal: Performance and mechanisms

Sodium, silicate and carbonate ions co-substituted hydroxyapatite adsorbent (Na-SiCHAP) was prepared by sonochemistry coprecipitation. The effect of a variety of parameters on the adsorption of Pb2+ and Cd2+ by Na-SiCHAP were performed. The adsorption process of heavy metal ions was found to follow the pseudo-second-order kinetic equation and Langmuir adsorption model. The maximum absorption capacity (Qm) of Na-SiCHAP for Pb2+ and Cd2+ ions in 303 K were 698.68 and 129.60 mg g−1 according to the Langmuir adsorption model, respectively. The thermodynamic parameters (ΔG0 <0, ΔS0 >0, ΔH0 >22kJ·mol-1) indicated that the absorption of Pb2+ and Cd2+ on the Na-SiCHAP was spontaneous and endothermic, and the Na-SiCHAP adsorbed mainly via chemical adsorption. Ion exchange of Pb2+ and Cd2+ for Ca2+ and Na+ was one of the principal mechanisms, followed by precipitation and electrostatic interactions. Furthermore, the well stability properties of the Na-SiCHAP adsorbent were confirmed by recycling assays. These data indicate that Na-SiCHAP may be a good adsorbent for the rapid removal of heavy metal ions from aqueous solutions.

Removal of Pb2+ from Aqueous Solution by Magnesium-Calcium Hydroxyapatite Adsorbent

A novel magnesium-calcium hydroxyapatite adsorbent was prepared by the Sol-gel method with different proportions of Mg/(Ca+Mg) using Mg2+ as doped ions, and the removal characteristics and process mechanism of Pb2+ on the magnesium-calcium hydroxyapatite in an aqueous solutions were studied. The results show that the surface of the adsorbent is composed mainly of a hydroxyphosphonite compound[Pb10(PO4)6(OH)2], The morphological characteristics of the magnesium-calcium hydroxyapatite adsorbent surface was investigated as crystal structure changes from short rods to needle structures according to scanning electron microscopy (SEM). Testing at a temperature of 25℃ and pH of 5 showed that the adsorption of Pb2+ by magnesium-calcium hydroxyapatite reached equilibrium within 720 min. The adsorption capacity was determined to be 813.17 mg·g-1 at a dosage of 0.6 g·L-1. The thermodynamic test results of ΔGθ<0, ΔSθ>0, and ΔHθ>0 indicated that the adsorption process of Pb2+ by magnesium-calcium hydroxyapatite is a spontaneous process with endothermic reaction and entropy increments, and higher temperatures were considered be favorable for adsorption at a range of 25-45℃. The adsorption could be effectively described by a pseudo-second-order kinetic equation. The equilibrium data were found to follow the Langmuir adsorption model. Material characterization and adsorption tests showed that surface complexation and dissolution-precipitation were the main mechanisms for the removal of Pb2+ by magnesium-calcium hydroxyapatite in an aqueous solution.

Eggshell-Derived Nanohydroxyapatite Adsorbent for Defluoridation of Drinking Water from Bofo of Ethiopia

Fluoride has become a notable toxicological environmental hazard worldwide because it is often found in groundwater. In the present study, hydroxyapatite adsorbent was synthesized from eggshell waste to remove fluoride from aqueous solution. XRD, FT-IR, and TGA techniques were used to characterize the prepared adsorbent. Batch adsorption studies were performed to examine the adsorption capacity of hydroxyapatite such as the effect of the initial pH of the solution, contact time, adsorbent dose, and initial fluoride concentration. The fluoride ion-selective electrode was used to determine the fluoride removal efficiency. 98.8% of fluoride was removed at pH 3.0, but at pH ~7.0, 85% of fluoride was removed; it shows that the fluoride adsorption is pH dependent. The adsorption isotherm studies (Langmuir and Freundlich models) and the experimental results for the removal of fluoride showed that the Langmuir model was more favorable and the reaction followed pseudo-second-order kinetics. In real water samples, the prepared hydroxyapatite derived from eggshell exhibited 81% removal efficiency. Our results indicate that eggshell waste-derived hydroxyapatite may be an alternative source for defluoridation in developing countries.

Rapid and effective removal of uranium (VI) from aqueous solution by facile synthesized hierarchical hollow hydroxyapatite microspheres.

Rapidly increasing development of nuclear power stimulates the exploration of low-cost and highly efficient materials to selectively remove uranium (VI) from contaminated wastewater streams. Herein, we successfully developed a novel hydroxyapatite (HAP) adsorbent by using a facile and template-free hydrothermal method. The XRD results demonstrated that the HAP was crystallized in hexagonal structure (space group P63/m(176)), and the images of SEM and TEM indicated that the HAP possessed hollow and hierarchical nanostructure. A large BET specific surface area (182.6 m2/g) and average pore size of 10.5 nm, suggested that the hierarchical hollow HAP microspheres could provide sufficient active sites for highly efficient removal of uranium from aqueous solutions, indicated the HAP might be a prompt emergency material for the remediation of nuclear leakage accident. Freundlich isotherm and pseudo-second-order kinetics model fitted well to sorption experimental data. The study was further advanced by FT-IR and XPS. The sorption mechanism was mainly attributed to surface chemisorption between U(VI) and HAP, forming a new U-containing compound, viz., autunite (Ca(UO2)2(PO4)2·3H2O).

Removing Lead and Cobalt Ions from Aqueous Solution by Hydroxyapatite Adsorbent

Removing Lead and Cobalt Ions from Aqueous Solution by Hydroxyapatite Adsorbent

Study on the removal of organic micropollutants from aqueous and ethanol solutions by HAP membranes with tunable hydrophilicity and hydrophobicity

A biocompatible and uniquely defined hydroxyapatite (HAP) adsorption membrane with a sandwich structure was developed for the removal of organic micropollutants for the first time. Both the adsorption and membrane technique were used for the removal of organic micropollutants. The hydrophilicity and hydrophobicity of the HAP adsorbent and membrane were tunable by controlling the surface structure of HAP. The adsorption of organic micropollutants on the HAP adsorbent was studied in batch experiments. The adsorption process was fit with the Freundlich model, while the adsorption kinetics followed the pseudo-second-order model. The HAP membrane could remove organic micropollutants effectively by dynamic adsorption in both aqueous and ethanol solutions. The removal efficiencies of organic micropollutants depended on the solution composition, membrane thickness and hydrophilicity, flow rate, and the initial concentration of organic micropollutants. The adsorption capacities of the HAP membrane with a sandwich structure (membrane thickness was 0.3 mm) were 6700, 6510, 6310, 5960, 5490, 5230, 4980 and 4360 L m−2 for 1-naphthyl amine, 2-naphthol, bisphenol S, propranolol hydrochloride, metolachlor, ethinyl oestradiol, 2,4-dichlorophenol and bisphenol A, respectively, when the initial concentration was 3.0 mg L−1. The biocompatible HAP adsorption membrane can be easily regenerated by methanol and was thus demonstrated to be a novel concept for the removal of organic micropollutants from both aqueous and organic solutions.

Kinetic approach for cadmium sorption using microwave synthesized nano-hydroxyapatite

Nano-crystalline hydroxyapatite adsorbent that was prepared by microwave processing was utilized for cadmium removal from aqueous solutions using the batch technique. Cadmium sorption on the prepared adsorbent was studied as a function of initial cadmium concentration in the aqueous solution, adsorbent dosage, agitation speed, hydrogen ion concentration of the aqueous solution (pH), and the solution temperature. The highest Cd 2+ sorption was achieved at agitation rate of 500 rpm. The sorption process was relatively fast and equilibrium was achieved after about 240 min of contact. The optimum sorption of cadmium occurred at pH range 4–7. The kinetic process of Cd 2+ sorption onto the synthesized nano-hydroxyapatite was tested by applying the pseudo-first order, the pseudo-second order, the simple Elovich and intraparticle diffusion rate models. The sorption process follows a pseudo second-order kinetics with a contribution of intraparticle diffusion. Thermodynamic parameters ΔH, ΔS and ΔG have been calculated. Positive value of ΔH and negative value of ΔG show endothermic and spontaneous nature of sorption respectively. The relatively small value of the activation energy that equal to 8.61 kJ/mol confirms that cadmium sorption process is diffusion controlled. The main mechanism for cadmium ions removal using the synthesized nano-hydroxyapatite was suggested to be ion-exchange and diffusion controlled.