Comparative study of differently treated animal bones for Co(2+) removal

Construction and demolition waste as a low-cost adsorbent for water treatment: kinetics, isotherm, thermodynamics, and Fenton regeneration

The present study proposes to investigate the feasibility of using construction and demolition waste (CDW) as an aqueous remediation agent through adsorption. The CDW, with and without chemical and thermal pre-activation, was evaluated to remove the methylene blue (MB) dye from the water solution. Variables interfering with adsorption processes, such as adsorbent dosage, solution pH, and particle size, were evaluated. The material was characterized by pHZPC, FTIR, XRD, SEM, EDS, and TG. The kinetic and equilibrium data better fitted the Elovich and Sips models, respectively. A maximum adsorption capacity of 18.62 mg g-1 at 60 °C was observed. Thermodynamic data indicated that adsorption occurred through a spontaneous and favorable process governed mainly by physical processes. The regeneration studies were carried out using processes based on the Fenton reaction, where the catalytic action of the iron naturally present in the CDW was evaluated. The results showed that the desorption balance was the main limiting factor for the effective regeneration of the saturated material. Adding Fe2+ to the system made this process suitable for the regeneration of the CDW and degradation of the pollutant in the aqueous phase. A regeneration efficiency of 65%, maintained practically constant during five adsorption-regeneration cycles, was observed. These results highlight the high potential of using CDWs as an adsorbent material.

Application of apatite particles for remediation of contaminated soil and groundwater: A review and perspectives

With rapid industrial development and population growth, the pollution of soil and groundwater has become a critical concern all over the world. Yet, remediation of contaminated soil and water remains a major challenge. In recent years, apatite has gained a surging interest in environmental remediation because of its high treatment efficiency, low cost, and environmental benignity. This review summarizes recent advances in: (1) natural apatite of phosphate ores and biological source; (2) synthesis of engineered apatite particles (including stabilized or surface-modified apatite nanoparticles); (3) treatment effectiveness of apatite towards various environmental pollutants in soil and groundwater, including heavy metals (e.g., Pb, Zn, Cu, Cd, and Ni), inorganic anions (e.g., As oxyanions and F-), radionuclides (e.g., thorium (Th), strontium (Sr), and uranium (U)), and organic pollutants (e.g., antibiotics, dyes, and pesticides); and (4) the removal and/or interaction mechanisms of apatite towards the different contaminants. Lastly, the knowledge or technology gaps are identified and future research needs are proposed.

Mixed solvent fabrication of tobermorite and the fixation of heavy metals in water and soil

Here, tobermorite was prepared by a solvothermal technology using calcite and quartz with a mixed solvent of ethanol and water. Factors including reaction temperature, time and KOH content were studied to optimize the preparation procedure. To study the relationship between ethanol content-material structural characteristics-adsorption capacity, a series of materials were prepared in different mixed solvent proportions of ethanol and water, and their structural characteristics and adsorption capacity were compared. We found that the adsorption capacity of different samples for Pb2+ and Cd2+ was positively correlated with negatively correlated with the surface area and negatively correlated with the crystallinity of materials. Then, the material prepared by 30% ethanol solution (30-T) with the best adsorption performance was used for further research; the results were fitted by kinetic and thermodynamic models, and adsorbed materials were analyzed by various characterizations, suggesting that the adsorption process was ascribed to comprehensive pathways including ion exchange, chemical precipitation, and surface-complexation. Then, the 30-T was further used to remediate heavy metals contaminated soil, and the remediation effect was examined by the DTPA-extractable method and the European Community Bureau of Reference (BCR) sequential extraction method. The DTPA-extractable results showed that tobermorite observably reduced the bioavailability of Pb and Cd, and the BCR results suggested that the acid-soluble and reducible fractions of Pb and Cd were transformed to the oxidizable and residual fractions after remediation. In summary, tobermorite has great potential in the remediation of heavy metal polluted-aquatic environment/system and soil.

Efficiency of chemically activated raw and calcined waste fish bone for Adsorption of Cd(II) and Pb(II) from polluted water.. [DOI: 10.21203/rs.3.rs-3103669/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Bone biochare is used widely as an adsorbent in water pollution control; because of its high surface area and pore volumes . This study is attempting to prepare a low cost adsorbent from waste fish bone by chemical activation, and uses it for the removal of Pb and Cd from polluted water. Two methods were used for preparation of fish bone adsorbents. The first method includes the chemical activation of waste fish bone using different chemical activators ( 0.001 M HNO3, 0.1 M NaOH, 0.5 % H2O2, and ethanol), while the second one includes calcination of waste fish bone after the chemical activation at 600oC. The synthesized fish bone adsorbents were characterized by electron microscopy (SEM), X-ray diffractometer (XRD), X-ray fluorescence (XRF), BET surface area, and Fourier transform infrared (FT-IR). The efficiency of the prepared adsorbents for removal of Pb and Cd were investigated as a function of contact time, solution pH, solution temperature, initial metal concentration, and adsorbent dose. Metal concentrations were measured by atomic absorption spectroscopy . The results reveal that activation of the waste fish bone by 0.1 M NaOH is the suitable for the higher adsorption of Pb and Cd than with the other activators. The maximum adsorption of Pb and Cd on the chemically prepared adsorbent were 99.74 and 99.35 % , respectively at optimum conditions. The results of kinetic adsorption obeyed a pseudo-second-order model. Freundlich and Langmuir isotherms were applied , and the adsorption was found to be fitted well with the Langmuir model. This study ended with the success for preparing an ecofriendly and low cost fish bone adsorbent from the waste fish bone, and used it for the removal of Pb and Cd from polluted water

Aspergillus niger-mediated release of phosphates from fish bone char reduces Pb phytoavailability in Pb-acid batteries polluted soil, and accumulation in fenugreek

Soil receiving discharges from Pb-acid batteries dismantling and restoring units (PBS) can have a high concentration of phytoavailable Pb. Reducing Pb phytoavailability in PBS can decline Pb uptake in food crops and minimize the risks to humans and the environment. This pot study aimed to reduce the concentration of phytoavailable Pb in PBS through Aspergillus niger (A. niger)-mediated release of PO₄^3- from fish bone [Apatite II (APII)] products. The PBS (Pb = 639 mg kg^-1 soil) was amended with APII powder (APII-P), APII char (APII-C), and A. niger inoculum as separate doses, and combining A. niger with APII-P (APII-P + A. niger) and APII-C (APII-C + A. niger). The effects of these treatments on reducing the phytoavailability of Pb in PBS and its uptake in fenugreek were examined. Additionally, enzymatic activities and microbial biomass carbon (MBC) in the PBS and the indices of plant physiology, nutrition, and antioxidant defense machinery were scoped. Results revealed that the APII-C + A. niger treatment was the most efficient one. Compared to the control, it significantly reduced the Pb phytoavailability (DTPA-extractable Pb fraction) in soil and its uptake in plant shoots, roots, and grain, up to 61%, 83%, 74%, and 92%. The grain produced under APII-C + A. niger were safe for human consumption as Pb concentration in grain was 4.01 mg kg^-1 DW, remaining within the permissible limit set by WHO/FAO (2007). The APII-C + A. niger treatment also improved soil pH, EC, CEC, MBC, available P content and enzymatic activities, and the fenugreek quality parameters. A. niger played a significant role in solubilizing PO₄^3- from APII-C, which reacted with Pb and formed insoluble Pb-phosphates, thereby reducing Pb phytoavailability in PBS and its uptake in plants. This study suggests APII-C + A. niger can remediate Pb-polluted soils via reducing Pb phytoavailability in them.

Adsorption of Co(II) ions using Zr-Ca-Mg and Ti-Ca-Mg phosphates: adsorption modeling and mechanistic aspects

The environmental pollution by toxic Co(II) ions had a negative impact on living organisms and water resources. The amorphous Zr-Ca-Mg and Ti-Ca-Mg phosphates with varied Zr and Ti content with the mesoporous structure (A_BET = 19-232 m²/g, V_des. = 0.075-0.370 cm³/g, D_des. = 6.2-10.9 nm) were synthesized. The effect of adsorbent chemical composition, the presence of competing ions (0.1-1.0 M NaCl and 0.01-0.1 M CaCl₂ backgrounds), and pH (3.0-7.0) of aqueous solution on adsorption removal of Co(II) ions by Zr-Ca-Mg and Ti-Ca-Mg phosphates was studied. The highest adsorption capacity of Zr-Ca-Mg-1 and Ti-Ca-Mg-1 samples reached 253.3 and 212.8 mg/g. The prepared adsorbents demonstrated high efficiency at pH in the range of 3.0-7.0 and the presence of 0.1-1.0 M NaCl and seawater with a salinity of 35.0 g/L backgrounds. The chemisorption and ion-exchange mechanisms of Co(II) ions removal for Zr-Ca-Mg and Ti-Ca-Mg phosphates were proposed. The adsorption isotherms were well fitted with Sips and Langmuir models that proved the heterogeneous nature of adsorption sites as well as assumed the monolayer adsorption that occurs at specific homogeneous sites within the adsorbent without any interaction between the adsorbed substances. The kinetic data was well described by the pseudo-second-order model that is suitable for chemisorption processes as liming adsorption stage. The presented results shown the prospects of developed adsorbents for the investigation of real wastewater treatment from heavy metal ions and liquid radioactive waste purification.

One stone two birds: Bone char as a cost-effective material for stabilizing multiple heavy metals in soil and promoting crop growth

Remediation of farmland soils contaminated with high levels of multiple heavy metals near PbZn smeltery is still a great challenge. It is of great significance to find cost-effective green remediation technologies for stabilization of multiple heavy metals in soil and reduce metal accumulation in crops with ensured yield. In this study, we demonstrated that bone char (BC) is an effective heavy metal stabilizer which can substantially increase residual fractions of heavy metals and reduce metal accumulation in pea (Pisum sativum) with its enhanced growth. We chose the soils contaminated with high levels of Pb, Zn, Cu and Cd near the Baiyin PbZn smeltery as the tested soil. After 2 months of BC application, the relative mobile fractions (non-residual fractions) of Cu, Zn, Pb and Cd in the contaminated soil decreased while the residual fraction increased significantly. The leachability of Cu, Zn, Pb and Cd decreased by 91.2%, 38.6%, 67.6% and 54.3%, respectively compared with the control. BC application remarkably promoted pea growth and reduced accumulation of heavy metals in shoots. The mechanisms for stabilization of multiple heavy metals BC include ion exchange, surface complexation and subsequent mineralization, accompanied with release of Ca and phosphate. The immobilization of heavy metals led to their reduced toxicity to plant, and thus increased pea growth. The results show that BC is a cost-effective and sustainable heavy metal stabilizer with phosphate fertilization function. It can simultaneously immobilize multiple heavy metals in soil and facilitate crop production.

Buckwheat hull-derived biochar immobilized in alginate beads for the adsorptive removal of cobalt from aqueous solutions

Buckwheat hull-derived biochar (BHBC) beads were synthesized by immobilizing biochar powder with alginate. Due to their cation-exchange ability, abundant functional groups, microporous structure, and large surface area, BHBC beads were successfully applied for the removal of cobalt from aqueous solution. The adsorption behavior followed pseudo-second-order kinetics and the Langmuir isotherm model showed a better fit to adsorption data than the Freundlich or Temkin isotherm models. The maximum adsorption capacity of BHBC beads was 24.0 mg/g at pH 5, 35 °C, and an initial cobalt concentration of 1.0 g/L, which was higher than those of previously reported natural resource-based adsorbents. In a fixed-bed column study, the effects of operating parameters such as flow rate, bed height, and bed diameter were investigated. Both the Thomas and Yoon-Nelson models were applied to the experimental data to predict the breakthrough curves using nonlinear regression. Overall, BHBC beads can be used as an efficient adsorbent for removal of radioactive cobalt from aqueous solution.

Polymeric Biomass Derived Adsorbents for Co(II) Remediation, Recycling and Analysis

The gradual replacement of conventional materials with materials tailored to the green development goals is one of the needs of the day. Correspondingly, this article reviews and integrates, for the first time, the gathered knowledge on the use of the adsorbents based on polymeric biomasses (biosorbents) for a cleaner separation of cobalt (Co) from synthetic and actual solutions. It is a two-part comprehensive approach that debates the Co biosorption potential of bio-based polymers from the perspective of their virtual and real applications for decontamination, recovery, and analytical purposes. First, the removal performances of these materials to batch and fixed column biosorption of Co(II) from mono-component and multi-metallic laboratory solutions are systematized and discussed. Following that, the focus of the first part is shifted to the analytical capabilities of the biosorbents proposed for Co(II) quantification from synthetic solutions. The second section considers the polymeric biomasses successfully incorporated in practical strategies for the removal and recovery of Co(II) from real solutions. The opportunities provided by the use of biosorbents for the development of accurate and greener procedures in Co(II) analysis are also highlighted. The directions in which the research on this topic should be continued and strengthened are suggested.

Sorption of Cd2+ on Bone Chars with or without Hydrogen Peroxide Treatment under Various Pyrolysis Temperatures: Comparison of Mechanisms and Performance

In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd2+ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and the number of oxygen-containing functional groups on the bone char surface increased. After being pyrolyzed, the specific surface area and the negative charge of the material were further improved. The adsorption kinetics and isotherms of Cd2+ adsorption were studied, and the influence of solution pH and the presence of ionic species were investigated. The experimental results showed that the samples with lower crystallinity exhibited less organic matter content and more surface oxygen-containing functional groups, resulting in stronger adsorption capacity. After being treated with hydrogen peroxide and pyrolyzed at 300 °C, the maximum adsorption capacity of bone char was 228.73 mg/g. The bone char sample with the lowest adsorption capacity(47.71 mg/g) was pyrolyzed at 900 °C without hydrogen peroxide pretreatment. Ion exchange, surface complexation, and electrostatic interactions were responsible for the elimination of Cd2+ by the bone char samples. Overall, this work indicates that hydrogen peroxide-treated pyrolytic bone char is a promising material for the immobilization of Cd2+.

Adsorption Performance of Cd(II) by Chitosan-Fe3O4-Modified Fish Bone Char

In order to develop a low-cost, fast, and efficient adsorbent, the fish bone charcoal B₆₀₀ prepared at 600 °C was modified by chitosan (Cs) and Fe₃O₄ to produce the material Cs-Fe₃O₄-B₆₀₀. Results showed that Cs-Fe₃O₄-B₆₀₀ had magnetic responsiveness and can achieve solid–liquid separation, macropores disappeared, pore volume and specific surface area are increased, and amino functional groups appear on the surface. The adsorption process of Cd(II) by Cs-Fe₃O₄-B₆₀₀ conformed best to the pseudo-second order kinetics model and the Langmuir model, respectively. The behavior over a whole range of adsorption was consistent with chemical adsorption being the rate-controlling step, which is a very fast adsorption process, and the isothermal adsorption is mainly monolayer adsorption, which belongs to favorable adsorption. In addition, the saturated adsorption capacity obtained for the Cs-Fe₃O₄-B₆₀₀ to Cd(II) was 64.31 mg·g⁻¹, which was 1.7 times than B₆₀₀. The structure and morphology of Cs-Fe₃O₄-B₆₀₀ were characterized through SEM-EDS, TEM, FTIR, and XRD, indicating that the main mechanism of Cs-Fe₃O₄-B₆₀₀ and Cd(II) is mainly the complexation of amino groups, and it also includes part of the ion exchange between Cd(II) and Fe₃O₄. Therefore, Cs-Fe₃O₄-B₆₀₀ can be employed as an effective agent for remediation of Cd contaminated water.

Adsorption characteristics of Pb(II), Cd(II) and Cu(II) on carbon nanotube-hydroxyapatite

Based on batch experiments, we investigate the adsorption characteristics of Pb(II), Cd(II) and Cu(II) on multi-walled carbon nanotube-hydroxyapatite (MWCNT-HAP) composites in detail and explore the effects of the solid-to-liquid ratio, pH, the ionic strength, reaction time and temperature on adsorption. The results show that the adsorption on MWCNT-HAP follows Pb(II)>Cu(II)>Cd(II). With an increasing solid-to-liquid ratio, the adsorption quantity of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP decreases, whereas the removal efficiency increases. The optimal pH for adsorption is 4.0∼6.0. The effect of the ionic strength on the adsorption of Cd(II) is pronounced, whereas that on the adsorption of Pb(II) and Cu(II) is small. In the single-component system and ternary-component system, the adsorption processes for Pb(II), Cd(II) and Cu(II) on MWCNT-HAP have fast kinetics, and the pseudo-second-order kinetics model can well describe the adsorption kinetics of the three heavy metals. The adsorption of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP is spontaneous and endothermic, and the Langmuir model can well simulate the isothermal adsorption of Pb(II) and Cu(II), whereas the Langmuir and Freundlich models can be used to describe the isothermal adsorption of Cd(II).

Trace element concentrations in the organs of fish along the southeast coast of India

Trace element pollution in the marine system is a global concern as the exposure of marine organisms to this pollution results in bioaccumulation and further transfer of the trace elements to humans through food chain. In the present study, the distribution of trace elements, namely chromium, cobalt, nickel, iron, copper, zinc, arsenic, cadmium, mercury, and lead, in gills, bone, liver, and muscle of eight commercially important fish collected along the southeast coast of India was analyzed using an inductively coupled plasma mass spectrometer. The liver was the main organ of accumulation for copper, zinc, arsenic, cadmium, and mercury; bone for chromium, cobalt, and lead; gills for copper; and muscle for arsenic and mercury. The concentration of toxic trace elements such as arsenic, cadmium, mercury, and lead in the edible portion of fish was lower than the recommended International Legislation limits, indicating that the fish of this region are safe for consumption.

Valorization of Eggshell Biowaste for Sustainable Environmental Remediation

The management of large amounts of eggshell waste annually produced in the world is problematic as generally this material is only disposed at landfills with odor production and microbial growth. On the contrary, significant environmental and economic advantages could be obtained transforming this biowaste into new value-added products. Eggshell biowaste was the starting material for the synthesis of hydroxyapatite by a simple and sustainable procedure and applied for the removal of Co²⁺ from aqueous solutions. The effects of contact time and initial metal concentration were investigated in batch experiments. Eggshell-based hydroxyapatite (ESHAP) before and after Co²⁺ removal was characterized by X-ray diffraction and scanning electron microscopy. The process was rapid and reached equilibrium within 80 min. The removal efficiency was in the range 70-80% which is generally higher than other waste-derived adsorbents. Adsorption of Co²⁺ on the surface of ESHAP particles and ion exchange with Ca²⁺ resulting in the formation of a Co-phosphate are the main mechanisms of the metal removal. The conversion of eggshell waste to a low-cost adsorbent for the treatment of metal contaminated waters could contribute to a more sustainable and effective management of this biowaste.

Effect of different pyrolysis temperatures on physico-chemical characteristics and lead(ii) removal of biochar derived from chicken manure

Biochar derived from chicken manure, as an effective metal adsorbent, was prepared through a pyrolysis method at different pyrolytic temperatures (200, 400, 600, and 800 °C). The physicochemical characteristics of chicken manure biochar (CMB) and its lead (Pb2+) adsorption mechanisms were studied by batch adsorption experiments, DTA/TGA, XRD, SEM-EDS, FTIR and an analysis of the composition of their mineral ash. Results showed that the best-fit for the Pb2+ adsorption data was achieved using a Langmuir isotherm and a pseudo-second-order model. The maximum adsorption capacities of Pb2+ increased with increasing of pyrolytic temperatures of the CMB, being 180.21, 200.80, 239.59, and 242.57 mg g-1, respectively, for CMB-200, CMB-400, CMB-600 and CMB-200. Although Pb2+ adsorption on CMB revealed that adsorption was controlled by multiple mechanisms, (e.g. surface complexation, ion exchange, surface precipitation, electrostatic attraction, physical adsorption, and co-precipitation), the ion exchange and surface precipitation played a dominant role in Pb2+ sorption. Using CMB for the removal of Pb from water is proposed as an effective, environmentally protective, novel approach.

Comparative evaluation of bone chars derived from bovine parts: Physicochemical properties and copper sorption behavior

With the increasing demand for beef worldwide, a considerable amount of bovine bone is discharged as solid waste. Therefore, in this study, the physicochemical properties of chars from bovine bones (ribs, scapulae, vertebrae, and legs) and their copper sorption behavior in aqueous solutions were investigated. The bone chars were pyrolyzed at 500 °C and the ash contents were approximately 85.08%, although the leg bone char had significantly higher values. The rib bone char showed a larger specific surface area (172 m²/g), smaller average pore diameter (7.7 nm), and more basic functional groups than the other char types. The maximum sorption capacity varied from 72.53 to 83.71 g/kg, with the rib bone char exhibiting the best adsorption characteristics, followed by the scapulae, vertebrae, and legs. A correlation analysis demonstrated that the adsorption capacity of Cu(II) on bone char is closely related to surface pore characteristics. An adsorption kinetic analysis and physicochemical characterization of the chars indicate that the Cu(II) adsorption mechanism in bovine bone char is primarily surface chemisorption. Based on the different of physicochemical properties and sorption behavior, bone chars pyrolyzed from bovine ribs are most suitable for adsorption-related applications. The results of this study demonstrate the potential for classified utilization of animal bones, including the use of graded bone chars as low-cost adsorbents requiring no chemical pre-treatment.

Optimization of Hg(II) adsorption on bio-apatite based materials using CCD-RSM design: characterization and mechanism studies

Bio-apatite based materials were prepared from bovine bone wastes (BBW) by thermal treatments using a direct flame (BBS) and annealing at 500-1,100 °C (BB500-BB1100). These low-crystalline materials were characterized by means of SEM, XRD, FTIR, TG, and pH_PZC and were used for the adsorption of Hg(II) ions. A CCD-RSM design was used to optimize and analyze independent variables consisting of initial mercury concentration (10-100 mg L^-1), pH (2-9), adsorbent mass (0.1-0.5 g), temperature (20-60 °C), and contact time (15-120 min). The results indicated that the order of the mercury uptakes for bio-apatite based adsorbents was BB500 > BB600 > BB800 > BB1100 > BBS > BBW. The dissolution-precipitation and ion-exchange reaction are the two dominant mechanisms for the removal of Hg(II) ions at low and high pH values, respectively. The CCD-RSM predicted maximum mercury adsorption of 99.99% under the optimal conditions of 51.31 mg L^-1, 0.44 g, 6.5, 67.5 min, and 50 °C for initial mercury concentration, adsorbent mass, pH, contact time, and temperature, respectively. The findings of the present study revealed that the bio-apatite based materials, particularly BB500, are suitable and versatile adsorbents for the treatment of mercury-containing wastewater.

Lead sorption characteristics of various chicken bone part-derived chars

Recycling food waste for beneficial use is becoming increasingly important in resource-limited economy. In this study, waste chicken bones of different parts from restaurant industry were pyrolyzed at 600 °C and evaluated for char physicochemical properties and Pb sorption characteristics. Lead adsorption isotherms by different chicken bone chars were carried out with initial Pb concentration range of 1-1000 mg L^-1 at pH 5. The Pb adsorption data were better described by the Langmuir model (R² = 0.9289-0.9937; ARE = 22.7-29.3%) than the Freundlich model (R² = 0.8684-0.9544; ARE = 35.4-72.0%). Among the chars derived from different chicken bone parts, the tibia bone char exhibited the highest maximum Pb adsorption capacity of 263 mg g^-1 followed by the pelvis (222 mg g^-1), ribs (208 mg g^-1), clavicle (179 mg g^-1), vertebrae (159 mg g^-1), and humerus (135 mg g^-1). The Pb adsorption capacities were significantly and positively correlated with the surface area, phosphate release amount, and total phosphorus content of chicken bone chars (r ≥ 0.9711). On the other hand, approximately 75-88% of the adsorbed Pb on the chicken bone chars was desorbable with 0.1 M HCl, indicating their recyclability for reuse. Results demonstrated that chicken bone char could be used as an effective adsorbent for Pb removal in wastewater.

The Effect of Calcium Deficiency on Bone Properties in Growing Rats

Background:

In this work, the study of the physicochemical properties of the rat bones that were fed under severe and moderate calcium depletion was carried out. Calcium depletion is a common problem in the diet of the third world.

Objective:

Three calcium levels: 5000, 2500, and 1039 mg/kg, were used in the diets to evaluate the influence of calcium deficiency on the bone quality by post-mortem tests.

Methods:

Inductive Coupled Plasma was used to study the elemental chemical composition of the bones; X-ray diffraction evaluated the bone structure and crystallinity; the microstructure and architecture were investigated using scanning electron microscopy; thermogravimetric analysis assessed the ratio between organic and inorganic phases of bones. All of these results were correlated with flexion and compression test determining the biomechanical properties to evaluate the bone quality.

Results:

The results showed that severe calcium depletion (75% depletion, 1039 mg/kg) was a critical factor in the unsuitable mineralization process responsible for the deterioration of bone quality. Bone architecture with delicate trabeculae caused the poor mechanical response. For moderate calcium depletion (50% of the request, 2500 mg/kg), the bone quality and its mechanical behavior showed less deterioration in comparison with bones of severe calcium depletion diet.

Conclusion:

By using this animal model, the effect of calcium depletion in bone mineralization in rats was understood and can be extrapolated for humans.

Cadmium retention and distribution in contaminated soil: effects and interactions of soil properties, contamination level, aging time and in situ immobilization agents

As soil cadmium (Cd) contamination becomes a serious concern and one of the significant environmental pollution issues all over the world, knowledge of the basic chemistry, origin, inputs, sources, quantity, chemical forms, reactions, as well as the fate and transport of Cd in different types of soil is crucial for better understanding Cd bioavailability, health risks and remedial options. This study aimed to increase the current knowledge on the complex interdependence between the factors affecting behavior, transport and fate of Cd in the soil and to test and compare the performance of the stabilization agents in different soil types. Soils demonstrated various sorption affinity and capacity for Cd accumulation, which proved to be positively correlated with soil pH and the cation exchange capacity (CEC). With increasing levels of contamination, sequential extraction analysis showed the highest increase of relative Cd amounts in the exchangeable fraction regardless of the soil properties, suggesting that added Cd is principally associated with the easily accessible and mobile fraction. For different initial Cd concentrations and soil types, Cd sorption reached the quasi-equilibrium within 24 h of contact. Prolonged aging (two months) influenced the natural stabilization of Cd in all types of soil, but only at low contamination level. The application of both, conventional (slaked lime Ca(OH)₂) and alternative phosphate-rich (annealed bovine bones B₄₀₀) amendments, resulted in Cd relocation and reduction of exchangeable Cd content. Although the effect was smaller when apatite amendment was utilized, observed re-distribution of Cd to more stable soil fractions is preferable for achieving long-term stabilization. Cd concentrations extracted in exchangeable and acid soluble fractions after the treatments of contaminated soil samples suggest that the practical applicability of in situ immobilization depends on the soil properties and the level of contamination, as well as that effect, should be monitored for the possible re-mobilization of Cd.

Bone char as a green sorbent for removing health threatening fluoride from drinking water

Millions of people around the world suffer from or prone to health problems caused by high concentration of fluoride in drinking water sources. One of the environmentally friendly and cost-effective ways for removing fluoride is the use of bone char. In this review, the structural properties and binding affinity of fluoride ions from different water sources was critically discussed. The effect of experimental conditions on enhancing the adsorption capacity of fluoride ions using bone char samples was addressed. It appears that surface properties, and conditions of the bone char production such as temperature and residence time play an important role in designing the optimal fluoride removal process. The optimum temperature for fluoride removal seems to be in the range of 500-700 °C and a residence time of 2 h. Applying various equilibrium adsorption isotherms for understanding fluoride adsorption mechanism was presented. The effect of bone char modification with different elements were discussed and recommendations for a further increase in the removal efficiency was proposed. Cost of bone char production and large-scale treatment systems were also discussed based on information available from scientific and commercial sources. Challenges with existing domestic defluoridation designs were highlighted and suggestions for new conceptual designs were provided.

Sorption of divalent heavy metal ions onto functionalized biogenic hydroxyapatite with caffeic acid and 3,4-dihydroxybenzoic acid

The sorption ability of biogenic hydroxyapatite (BHAP) towards heavy metal ions (Pb, Cu, Ni, Cd, and Zn) is compared with functionalized BHAP powders with caffeic acid (CA) and 3,4-dihydroxybenzoic acid (3,4-DHBA). The functionalization of the BHAP with either CA or 3,4-DHBA is indicated by the appearance of the colored powders due to the formation of the interfacial charge transfer (ICT) complexes. The detailed characterization of as-prepared and functionalized BHAP samples was performed using transmission electron microscopy, reflection spectroscopy, thermogravimetric analysis and determination of zeta potential. All three sorbents clearly displayed preferential sorption of Pb ions when the total concentration of multi-component equimolar solutions of heavy metal ions is high. It should be emphasized that the sorption capacity of functionalized BHAP with either CA or 3,4-BHAP was found to be higher, up to 60%, compared to as-prepared BHAP without the decrease of selectivity towards Pb ions.

The use of sea shell (Donax trunculus) powder to remove Sr(II) ions from aqueous solutions

This study aimed to investigate and explore the possibility of using ground sea shell powder (Donax trunculus) (SSP) for sorption of Sr(II) ions from aqueous solutions. The maximum removal of Sr(II) removal in SSP was 60% at initial Sr(II) concentration of 25 mg/L, at pH 6.0, contact time 120 min, temperature 25 °C and volume/mass ratio equivalent to 500. Sorption data were interpreted considering the adsorption isotherms and thermodynamic parameters calculated. The maximum Sr(II) adsorption on SSP was 25.45 mg/g at pH 6.0. Freundlich isotherm and Dubinin-Radushkevich models were seen to be more compatible with the sorption equilibrium. The nature of the process was spontaneous and exothermic. The results suggest that SSP could be used as an efficient and cost-effective adsorbent to remove strontium ion.

Optimization of Pb(II) ions adsorption on nanohydroxyapatite adsorbents by applying Taguchi method

This paper presents an optimization approach for the removal of lead ions (Pb⁺²) by nano-hydroxyapatite powder form adsorbents that were produced from bovine bone by mechanical activation method. The Taguchi method was implemented for designing the experiments by considering four controllable factors including (1) ball milling time (A), (2) the initial concentration of lead ions (B), (3) initial pH of the solution (C); and (4) the adsorbent dosage (D), each factor at four different levels. According to the ANOVA analysis results, the removal efficiency of the lead ions was predominantly influenced by the adsorbent dosage (38.2%) and the initial lead ions concentration (23.64%), whereas the effect of initial pH of the solution was ignorable and the ball milling time had a mild contribution of 14.79%. The total optimum adsorptive lead ions removal of 100% was achieved by optimization process at operating conditions of C_o = 180 mg L^{- 1}, ball milling time = 2 h, pH = 3, and adsorbent dosage = 0.15 g. The Langmuir isotherm model fitted to the equilibrium results with good accuracy and a maximum sorption capacity of 200 mg g^-1 was predicted by the model for the hydroxyapatite adsorbent ball milled for 2 h.

Kinetic and thermodynamic studies of the Co(II) and Ni(II) ions removal from aqueous solutions by Ca-Mg phosphates

The aim of this work was to study the sorption kinetics and thermodynamics of Co(II) and Ni(II) from aqueous solutions by sorbents on the basis of hydrogen (PD-1) and tertiary (PD-2) Ca-Mg phosphates depending on the solution temperature and sorbents chemical composition. Kinetic studies of adsorption of Co(II) and Ni(II) ions onto samples of phosphate sorbents were performed in batch experiment at the temperatures 288, 303, 318 and 333 K. The sorbent dose was fixed at 10 g L^-1, initial pH value 2.6, and contact time varied from 5 to 600 min. The kinetics of Co(II) and Ni(II) adsorption were analyzed by using pseudo-first order, pseudo-second order and intraparticle diffusion models. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for the sorption of Co(II) and Ni(II) were determined using the Gibbs-Helmholtz equation. The calculated kinetic parameters and corresponding correlation coefficients revealed that Co(II) and Ni(II) uptake process followed the pseudo-second order rate expression. Thermodynamic studies confirmed the spontaneous and endothermic nature of removal process which indicate that sorption of Co(II) and Ni(II) ions onto both phosphate sorbents is favoured at higher temperatures and has the chemisorptive mechanism. The data thus obtained would be useful for practical application of the low cost and highly effective Ca-Mg phosphate sorbents.

Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N₂-BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q = 6.2 ± 0.5 mg/g) and Al-doped (q = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C ₀ → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F^-/L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F^-]_feed ∼ 9 mg/L; flow rate = 1 mL/min; m _sorbent = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

Competitive adsorption of toxic metals on bentonite and use of chitosan as flocculent coagulant to speed up the settling of generated clay suspensions

Evaluation of modified Algerian clay as mineral adsorbent was done for its adsorbing capacity on copper (Cu) and Zinc (Zn) cations. The results obtained show a rapid kinetic adsorption for both metals (less than 2 h) following the pseudo-second order model with high elimination rates of 67.2 and 61.8% for Cu and Zn respectively. The adsorption isotherms analyzed with Langmuir model revealed a correlation with the experimental values. While the use of obtained chitosan at room temperature, as flocculent coagulant, accelerates the decantation of the colloidal particles in suspension generated after adsorption process.

Utilization to Remove Pb (II) Ions from Aqueous Environments Using Waste Fish Bones by Ion Exchange

Removal of lead (II) from aqueous solutions was studied by using pretreated fish bones as natural, cost-effective, waste sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacities of the adsorbent was investigated. The maximum adsorption capacity for Pb (II) was found to be 323 mg/g at optimum conditions. The experiments showed that when pH increased, an increase in the adsorbed amount of metal of the fish bones was observed. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of Pb (II) adsorption and the value ofRLfor Pb (II) was found to be 0.906. The thermodynamic parameters related to the adsorption process such asEa,ΔG°,ΔH°, andΔS° were calculated andEa,ΔH°, andΔS° were found to be 7.06, 46.01 kJ mol−1, and 0.141 kJ mol−1K−1for Pb (III), respectively.ΔH° values (46.01 kJmol−1) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to the experimental equilibrium data. The fish bones were effectively used as sorbent for the removal of Pb (II) ions from aqueous solutions.

Evaluation of factors influencing Co²⁺ removal by calcinated bone sorbent using experimental design methodology

Experimental design methodology was applied for evaluation of factors influencing Co(2+) sorption by thermally treated bovine bones. The major aim of this study was to determine factors which affect process the most, as well as their mutual interactions, in order to select conditions that provide maximum sorbent loading. Five process variables (sorbent mass, sorbate concentration, contact time, initial pH and agitation speed) were examined by full factorial design at two levels. The initial sorbate concentration and sorbent mass were found to be a principle factors influencing cation sorption. Furthermore, a considerable interaction effect between these two factors was detected. Optimal conditions for the maximum sorbent loading include the use of small sorbent doses and concentrated Co(2+) solution, without any previous pH adjustment, at least if the pH of actual waste water is within tested range (3 < pH < 6). The contact time and agitation speed, which within investigated ranges had no significant effect on sorption, may be set at their minimum levels (1 h; 10 rpm) to shorten the reaction time and reduce energy consumption. The influence of process factors on other system responses (amounts of Ca(2+) released from apatite phase of bones, and final pH values) were also determined and analyzed. Empirical mathematical models illustrated the dependences of responses on the process variables, whereas residual and statistical analysis confirmed model adequacy.

Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite II™: column experiments

Apatite II™, a biogenic hydroxyapatite, was evaluated as a reactive material for heavy metal (Cd, Cu, Co, Ni and Hg) removal in passive treatments. Apatite II™ reacts with acid water by releasing phosphates that increase the pH up to 6.5-7.5, complexing and inducing metals to precipitate as metal phosphates. The evolution of the solution concentration of calcium, phosphate and metals together with SEM-EDS and XRD examinations were used to identify the retention mechanisms. SEM observation shows low-crystalline precipitate layers composed of P, O and M. Only in the case of Hg and Co were small amounts of crystalline phases detected. Solubility data values were used to predict the measured column experiment values and to support the removal process based on the dissolution of hydroxyapatite, the formation of metal-phosphate species in solution and the precipitation of metal phosphate. Cd(5)(PO(4))(3)OH(s), Cu(2)(PO(4))OH(s), Ni(3)(PO(4))(2)(s), Co(3)(PO(4))(2)8H(2)O(s) and Hg(3)(PO(4))(2)(s) are proposed as the possible mineral phases responsible for the removal processes. The results of the column experiments show that Apatite II™ is a suitable filling for permeable reactive barriers.

The effect of process parameters on kinetics and mechanisms of Co2+ removal by bone char

Bone char powder, composed mainly of poorly crystalline hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)), carbon and CaCO(3), has potential applicability in the removal of Co(2+) ions from contaminated effluents. In the present study, the influence of process parameters: particle size, agitation speed, initial pH and initial sorbate concentration, onto kinetics and mechanism of Co(2+)sorption was studied and discussed. In order to describe and compare time evolution of the process under different conditions, the experimental data were analyzed using pseudo-first, pseudo-second and Vermeulen's kinetic models. Generally, experimental results were best fitted with the pseudo-second-order model, which accurately predicted the equilibrium sorbed amounts. The pseudo-second-order rate constant was the most influenced by variations in initial metal concentration and pH, in the investigated ranges. The conclusions about sorption mechanism were derived based on Co(2+) amounts sorbed during time, as well as considering solution pH changes, changes of Ca(2+) amounts released into liquid phase and Ca(2+)/Co(2+) molar ratios. It was concluded that rapid sorption stage was governed by surface complexation reactions, whereas the contribution of the ion-exchange mechanism increased with time and became more significant in the second, slower phase. Experimentally determined maximum sorption capacity towards Co(2+), under optimal conditions, was found to be 0.38 mmol/g. The results show that bone char represents cost-effective alternative to synthetic hydroxyapatite sorbent.