Effect of pyrolysis conditions on bone char characterization and its ability for arsenic and fluoride removal

Kinetics study and Py-GC-MS analysis of pyrolysis in chicken bone waste for sustainable utilisation in thermal conversion

Chicken bone waste is generated by the food service industry and individual households. The main issues in bone waste management are related to illegal discharge or high disposal costs. However, their valorisation raises great prospects towards the achievement of environmental sustainability and circular bioeconomy. In this study, chicken bone waste feedstocks were sourced from the fried chicken process (CBF) and purchased from one of the world's largest fast-food restaurant chains as well as from household waste (CBO). The feedstocks were enzymatically pretreated, in preparation to be subjected to further processes, and then sonicated, dried, and milled. The elemental analysis revealed that both CBF and CBO had similar carbon, hydrogen, and nitrogen contents (c.a. 28% C, 4.5% H and 5% N). Mineral analysis showed calcium and phosphorus as key components, with phosphorus increasing and calcium decreasing after pyrolysis due to thermal degradation of calcium carbonate. The pyrolysis results demonstrated significant differences in kinetic parameters and reactivity. CBF, derived from pressure frying, displayed a lower temperature for the initial decomposition peak and a higher rate of volatile release compared to CBO. The activation energy profiles showed that while both samples had similar average activation energies (approximately 201-202 kJ/mol), CBF exhibited higher reactivity and a faster release of volatiles (total reactivity index RMtot 0.0305), and higher CPI indices for all elementary steps, and higher pyrolysis stability indexes Rw. Pyrolysis of CBF and CBO was modelled by applying the isoconversional Friedman method with fit quality R2 > 0.999. Pyrolysis (Py-Gc-MS) of chicken bone at 500 °C and 700 °C indicated a dominance of hydrocarbons and nitrogen-containing compounds, with CBF having higher fatty acid content due to frying oil residues. These findings highlight the influence of cooking methods on the pyrolytic behaviour of chicken bone waste, providing valuable insights for optimizing biochar production and other applications involving organic waste pyrolysis.

Organic manures reduce the bioavailability of fluoride in soil via different mechanisms

Fluoride (F) pollution in soils, which can be caused by long-term application of phosphate fertilizers, has serious socio-economic and ecological impacts. Therefore, it is important to find economically viable and environmentally friendly remediation technologies that mitigating the potential hazards of F-contaminated soil while maintaining crop yields. In this study, a soil incubation experiment was carried out to investigate the effects of two different organic manures at various amounts on soil F content and soil properties. We demonstrated that organic manure application at a rate of 5% was optimal to control the content of available fluoride (AE-F) in soil. Organic manure decreased the AE-F content and increased the residual or organically bound content. Furthermore, organic manure application also increased the contents of carbohydrates, proteins, and amides, which can anchor AE-F to the dissolved organic matter (DOM) in soil through physicochemical reactions, thereby reducing the migration of F. Moreover, after organic manure application, complex humus compounds were formed through microbial action, thus reducing the bioavailability of soil F. In summary, the application of organic manures can reduce the accumulation of soil AE-F, thereby reducing the absorption of F by crops in F-contaminated soil and alleviating the potential risk of F contamination.

A Novel Method for the Enhancement of Sunflower Growth from Animal Bones and Chicken Feathers

The present study aimed at converting meat industry waste, particularly waste bones and chicken feathers, into biochar to recycle valuable nutrients present in it, which ultimately become part of the municipal waste. The bone biochar (BB) and feathers biochar (FB) were prepared at 550 °C, and their potential was evaluated as an organic amendment for the growth of sunflower. The ash content (AC) and fixed carbon (FC) improved significantly in prepared biochars as compared to raw feedstock. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses signaled the occurrence of various functional groups viz. amide group and hydroxyapatite, porosity, and multiple nutrients. Application of BB and FB in potted soil alone as well as in composites (1:1, 1:2, 2:1) at 1%, 3%, and 5% (w/w) and synthetic fertilizer significantly increased soil pH, electrical conductivity (ECe), organic matter (OM) and water holding capacity (WHC), while reducing the bulk density (BD). The growth of plants grown in soil treated with a 2:1 composite of feathers and bone biochar at 5% application rate showed significantly greater differences in plant height, total chlorophyll content, and plant dry weight than the control but was comparable to growth with chemical fertilizer, rendering it a potential alternative to chemical-based synthetic fertilizer.

Uncovering nano-bonechar for attenuating fluoride in naturally contaminated soil

Fluoride ion (F-) is one of the major geogenic contaminants in water and soil. Excessive consumption of these geogenic contaminants poses serious health impacts on humans and plants. In this study, a novel carbonaceous material, nano-bonechar, was synthesized from cow bones and applied as a soil amendment at rates of 0, 0.5, 1, and 2% to remediate and revitalize naturally F--contaminated soil. The results revealed that the nano-bonechar significantly reduced the mobility and bioavailability of F- by 90% in the contaminated soil, and improved the soil quality by increasing the soil water holding capacity, soil organic matter, and the bioavailable contents of PO43-, Ca2+, and Na+. Subsequently, the pot experiment results showed a significant reduction in the uptake of F- by 93% in Zea mays plants. Moreover, the nano-bonechar application improved the plant's growth, as indicated by the higher fresh and dry weights, root and shoot lengths, and total content of PO43-, Ca2+, and K+ than those of un-amended soil. The F-immobilization in soil was mainly due to the presence of the hydroxyapatite [Ca10(PO4)6(OH)2] mineral in the nano-bonechar. Ion exchange between OH- (of nano-bonechar) and F- (of soil), and the formation of insoluble fluorite (CaF2) contributed to the attenuation of F- mobility in the soil. It is concluded that nano-bonechar, due to its size and enrichment in hydroxyapatite, could successfully be utilized for the rapid remediation and revitalization of F--contaminated agricultural soil.

A comprehensive study of artificial neural network for sensitivity analysis and hazardous elements sorption predictions via bone char for wastewater treatment

Using bone char for contaminated wastewater treatment and soil remediation is an intriguing approach to environmental management and an environmentally friendly way of recycling waste. The bone char remediation strategy for heavy metal-polluted wastewater was primarily affected by bone char characteristics, factors of solution, and heavy metal (HM) chemistry. Therefore, the optimal parameters of HM sorption by bone char depend on the research being performed. Regarding enhancing HM immobilization by bone char, a generic strategy for determining optimal parameters and predicting outcomes is crucial. The primary objective of this research was to employ artificial neural network (ANN) technology to determine the optimal parameters via sensitivity analysis and to predict objective function through simulation. Sensitivity analysis found that for multi-metals sorption (Cd, Ni, and Zn), the order of significance for pyrolysis parameters was reaction temperature > heating rate > residence time. The primary variables for single metal sorption were solution pH, HM concentration, and pyrolysis temperature. Regarding binary sorption, the incubation parameters were evaluated in the following order: HM concentrations > solution pH > bone char mass > incubation duration. This approach can be used for further experiment design and improve the immobilization of HM by bone char for water remediation.

Water-based technologies for improving water quality at the point of use: A review

Water safety concerns are increasing tremendously as a result of the rising population and environmental pollution. As a result, viable water treatment approaches need to be designed to meet the water consumption demands of the population, particularly in developing countries. The recent technological advances in water treatment and purification are well articulated in this review. The efficiency of the materials used for purification and their affordability for people living in rural and remote settlements in various parts of the world have been discussed. Water treatment techniques prior to the rapid advancement of science and technology included a variety of strategies such as coagulation/flocculation, filtration, disinfection, flotation and pH correction. The use of nanotechnology in water treatment and purification has modernized the purification process. Therefore, efficient removal of microbes such as bacteria and viruses are exquisitely accomplished. These technologies may include membrane filtration, ultraviolet irradiation, advanced oxidation ion-exchange and biological filtration technologies. Thus, nanotechnology allows for the fabrication of less expensive systems, allowing even low-income people to benefit from it. Most developing countries find these technologies particularly valuable because access to clean and safe water for drinking and residential needs is critical. This is because access to municipal water supplies is also difficult. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Preparation, characterisation and applications of bone char, a food waste-derived sustainable material: A review

The production of increasing quantities of by-products is a key challenge for modern society; their valorisation - turning them into valuable compounds with technological applications - is the way forward, in line with circular economy principles. In this review, the conversion of bones (by-products of the agro-food industry) into bone char is described. Bone char is obtained with a process of pyrolysis, which converts the organic carbon into an inorganic graphitic one. Differently from standard biochar of plant origin, however, bone char also contains calcium phosphates, the main component of bone (often hydroxyapatite). The combination of calcium phosphate and graphitic carbon makes bone char a unique material, with different possible uses. Here bone chars' applications in environmental remediation, sustainable agriculture, catalysis and electrochemistry are discussed; several aspects are considered, including the bones used to prepare bone char, the preparation conditions, how these affect the properties of the materials (i.e. porosity, surface area) and its functional properties. The advantages and limitations of bone chars in comparison to traditional biochar are discussed, highlighting the directions the research should take for bone chars' performances to improve. Moreover, an analysis on the sustainability of bone chars' preparation and use is also included.

Biochar modification to enhance arsenic removal from water: a review

Arsenic (As) contamination is a major threat to drinking water quality throughout the world, and the development of appropriate remediation methods is critical. Adsorption is considered the most effective method for remediation of As-contaminated water. Biochar is a promising adsorbent and widely discussed for As removal due to its potential low cost and environmental friendliness. However, pristine biochar generally exhibited relatively low adsorption capacity for As mainly due to the electrostatic repulsion between the negatively charged biochar and As. Biochar modification, especially metal modification, was developed to boost the adsorption capacity for As. A systematic analysis of As removal as affected by biochar properties and modification will be of great help for As removal. This paper presents a comprehensive review on As removal by biochars from different feedstock, preparation procedures, and modification methods, with a major focus on the possible mechanisms of interaction between As and biochar. Biochar derived from sewage sludge exhibited relatively high adsorption capacity for As. Considering energy conservation, biochars prepared at 401-500 °C were more favorable in adsorbing As. Fe-modified biochar was the most popular modified biochar for As remediation due to its low cost and high efficiency. In addition, the limitations of the current studies and future perspectives are presented. The aim of this review is to provide guidance for the preparation of low-cost, environmentally friendly, and high efficiency biochar for the remediation of As-contaminated water.

Water reclamation from anodizing wastewaters by removing reactive silica with adsorption and precipitation methods

Water stress is a current environmental menace mainly driven by over exploitation of aquifers, which is triggering poor water quality with high concentration of minerals in extracted groundwater. Particularly, silica is widespread in natural water supplies due to weathering processes of silicates occurring in contact with water, light, air, and other factors. However, due to groundwater over extraction the concentration of silica has increased during the last years in aquifer reservoirs from Aguascalientes State (México). In this context, it is very important to note that the removal of silica compounds from water is challenging and different methods can be used to avoid embedding problems in different industries. In the present work, the removal of reactive silica from synthetic solutions as well as from real wastewaters from an industrial anodizing process was studied using adsorption and chemical precipitation methods. Twelve commercial materials of different nature were used for adsorption tests, while seven precipitant agents were applied in the precipitation experiments. Adsorption tests were performed in batch systems with constant stirring at 30 °C and at different pH values (7 and 9). Precipitation experiments were carried out in batch systems and the best conditions for silica removal were found using an L₉ orthogonal array of the Taguchi method employing molar ratio, pH of wastewater, stirring time and temperature as experimental factors. Adsorption results showed that Ferrolox (Iron (III) hydroxide-base adsorbent) was the most efficient sorbent for reactive silica removal from synthetic solutions and the anodizing wastewater. Also, the reactive silica adsorption was higher at pH 9 as compared to that measured at pH 7 and the adsorbed quantity at pH 9 was 16.22 and 11.25 mg/g for the synthetic solution and anodizing wastewater, respectively. According to molecular simulation, the main interaction between Ferrolox and silica species was related to the formation of hydroxo-complexes and to the interaction of Fe with oxygen of silica species. Additionally, magnesium chloride was the best precipitating reagent for reactive silica achieving up to 87% removal. According to ANOVA analysis of Taguchi method, pH was the most influential factor during the precipitation of reactive silica with a variance value of 81.42, while values lower than 3 were obtained for the rest of parameters. Overall, the present work is reporting for the first time the removal of reactive silica from anodizing wastewaters with promising results that can be implemented at full scale for water reclamation, which may significantly contribute to manage water reservoir in the region sustainably.

Effects of additives on the co-composting of forest residues with cattle manure

Co-composting of forest residues (FR) with cattle manure (CM) results in a low nitrogen (N) conversion efficiency, a low organic matter (OM) degradation rate, and a low quality compost product. This study evaluated the effects of addition of bone charcoal (BC), pumice (PM), or straw biochar (SB) at a ratio of 10 % (w/w) on the co-composting of FR with CM. The highest quality compost was obtained with addition of 10 % PM. Compared with the control (without any additive), PM addition increased the OM degradation rate, the nitrate-N, the available phosphorus, and the available potassium by 25 %, 110 %, 24 %, and 9 %, respectively, and increased the relative abundance of bacteria (Planomicrobium, Flavobacterium, and Pseudomonas) involved in lignocellulose degradation and N transformation. With the addition of PM, the co-composting of FR with CM generated a high quality, useful product in only 39 days.

Applications of biomass-based materials to remove fluoride from wastewater: A review

Fluoride is one of the essential trace elements for the human body, but excessive fluoride will cause serious environmental and health problems. This paper summarizes researches on the removal of fluoride from aqueous solutions using newly developed or improved biomass materials and biomass-like organic materials in recent years. These biomass materials are classified into chitosan, microorganisms, lignocellulose plant materials, animal attribute materials, biological carbonized materials and biomass-like organic materials, which are explained and analyzed. By comparing adsorption performance and mechanism of adsorbents for removing fluoride, it is found that carbonizing materials and modifying adsorbents with metal ions are more beneficial to improving adsorption efficiency and the adsorption mechanisms are various. The adsorption capacities are still considerable after regeneration. This paper not only reviews the properties of these materials for fluoride removal, but also focuses on the comparison of materials performance and fluoride removal mechanism. Herein, by discussing the improved adsorption performance and research technology development of biomass materials and biomass-like organic materials, various innovative ideas are provided for adsorbing and removing contaminants.

Biogenic Hydroxyapatite Obtained from Bone Wastes Using CO2-Assisted Pyrolysis and Its Interaction with Glyphosate: A Computational and Experimental Study

In this work, biogenic hydroxyapatite (BHap) obtained from cattle bone waste is proposed as an adsorbent of this dangerous pollutant. Density functional theory (DFT) and calorimetric studies were developed to study the interaction between BHap and glyphosate (GLY). A strong interaction was found in the experiments through the measurement of immersion enthalpy, confirmed by the exothermic chemisorption obtained with DFT calculations. These results suggest that hydroxyapatite is a promising adsorbent material for GLY adsorption in aqueous solutions. In addition, it was determined that the GLY-hydroxyapatite interaction is greater than the water-hydroxyapatite interaction, which favors the GLY adsorption into this material.

Enhancement of anaerobic fermentation with corn straw by pig bone-derived biochar

Different sources of biochar exhibit different effects on anaerobic fermentation. Here, the effects of activation temperature, activation time, impregnation ratio, and pickling times on the properties of pig bone-derived biochar additives were explored by orthogonal experiments. The pig bone-derived biochar with better performance was optimized to enhance the anaerobic fermentation. The results showed that when the preparation conditions of biochar were as follows: activation temperature of 700 °C, impregnation ratio of 2, activation time of 90 min, and pickling times of 2, the cumulative methane production of corn stalk by anaerobic fermentation exhibited the highest value of 164.54 mL/g VS, which was 68% higher than the control group. The correlation between the characteristics of biochar for promoting anaerobic fermentation and the performance of anaerobic fermentation was established. Interestingly, the pig bone-derived biochar can buffer pH value in straw anaerobic fermentation.

As and F − cooccurrence in drinking water: critical review of the international scenario, physicochemical behavior, removal technologies, health effects, and future trends

Drinking water contaminated with As andF − is increasingly prevalent worldwide. Their coexistence can have negative effects due to antagonistic or synergistic mechanisms, ranging from cosmetic problems, such as skin lesions and teeth staining, to more severe abnormalities, such as cancer and neurotoxicity. Available technologies for concurrent removal include electrocoagulation ~ adsorption > membranes > chemical coagulation > , and among others, all of which have limitations despite their advantages. Nevertheless, the existence of competing ions such as silicon > phosphate > calcium ~ magnesium > sulfate > and nitrate affects the elimination efficiency. Mexico is one of the countries that is affected by As andF − contamination. Because only 10 of the 32 states have adequate removal technologies, more than 65% of the country is impacted by co-presence problems. Numerous reviews have been published concerning the elimination of As orF − . However, only a few studies have focused on the simultaneous removal. This critical review analyzes the new sources of contamination, simultaneous physicochemical behaviors, available technologies for the elimination of both species, and future trends. This highlights the need to implement technologies that work with actual contaminated water instead of aqueous solutions (55% of the works reviewed correspond to aqueous solutions). Similarly, it is necessary to migrate to the creation of pilot, pre-pilot, or prototype scale projects, because 77% of the existing studies correspond to lab-scale research.

Microbial induced calcium precipitation based anaerobic immobilized biofilm reactor for fluoride, calcium, and nitrate removal from groundwater

In this study, the anaerobic quartz sand fixed biofilm reactor containing Cupriavidus sp. W12 was established to simultaneously remove calcium (Ca²⁺), fluoride (F^-) and nitrate (NO₃^-N) from groundwater. After 84 days of continuous operation, the optimum operating parameters and defluoridation mechanism were explored, and the microbial community structure under different pH environments were compared and analyzed. Under the optimal operation conditions (HRT of 6 h, initial Ca²⁺ concentration of 180 mg L^-1, and pH of 7.0), the removal efficiencies of Ca²⁺, F^-, and NO₃^-N were 58.97%, 91.93%, and 100%, respectively. Gas chromatography (GC) results indicate that N₂ is the main gas produced by the bioreactor. Three-dimension excitation emission matrix fluorescence spectroscopy (3D-EEM) showed that extracellular polymers (EPS) are produced during bacterial growth and metabolism. The results of Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectrometer (FTIR) demonstrated that the defluoridation mechanism is attributed to the synergetic effects of ion exchange, co-precipitation, and chemisorption. The comparative analysis of the microbial community structure under different pH conditions show that Cupriavidus is the dominant bacteria in the bioreactor throughout the experiment, and it shows a prominent advantage at pH of 7.0. This research provides an application foundation for anaerobic microbial induced calcium precipitation (MICP) bioremediation of Ca²⁺, F^-, and NO₃^-N from groundwater.

Removal of potentially toxic elements from contaminated soil and water using bone char compared to plant- and bone-derived biochars: A review

Conversion of hazardous waste materials to value-added products is of great interest from both agro-environmental and economic points of view. Bone char (BC) has been used for the removal of potentially toxic elements (PTEs) from contaminated water, however, its potential BC for the immobilization of PTEs in contaminated water and soil compared to bone (BBC)- and plant (PBC)-derived biochars has not been reviewed yet. This review presents an elaboration for the potentials of BC for the remediation of PTEs-contaminated water and soil in comparison with PBC and BBC. This work critically reviews the preparation and characterization of BC, BBC, and PBC and their PTEs removal efficiency from water and soils. The mechanisms of PTE removal by BC, BBC, and PBC are also discussed in relation to their physicochemical characteristics. The review demonstrates the key opportunities for using bone waste as feedstock for producing BC and BBC as promising low-cost and effective materials for the remediation of PTEs-contaminated water and soils and also elucidates the possible combinations of BC and BBC aiming to effectively immobilize PTEs in water and soils.

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+.

Effects of torrefaction on product distribution and quality of bio-oil from food waste pyrolysis in N2 and CO2

Waste food utilization to produce bio-oil through pyrolysis has received increasing attention. The feedstock can be utilized more efficiently as its properties are upgraded. In this work, the mixed food waste (MFW) was pretreated via torrefaction at moderate temperatures (250-275 °C) under an inert atmosphere before fast pyrolysis. The pyrolysis of torrified MFW (T-MFW) was performed in a bubbling fluidized-bed reactor (FBR) to study the influence of torrefaction on the pyrolysis product distribution and bio-oil compositions. The highest liquid yield of 39.54 wt% was observed at a pyrolysis temperature of 450℃. The torrefaction has a significant effect on the pyrolysis process of MFW. After torrefaction, the higher heating values (HHVs) of the pyrolysis bio-oils (POs) ranged from 31.51 to 34.34 MJ/kg, which were higher than those of bio-oils from raw MFW (27.69-31.58 MJ/kg). The POs mainly contained aliphatic hydrocarbons (alkenes and ketones), phenolic, and N-containing derivatives. The pyrolysis of T-MFW was also carried out under the CO2 atmosphere. The application of CO2 as a carrier gas resulted in a decrease in the liquid yield and an increase in the gas product yield. In addition, the carbon and nitrogen content of POs increased, whereas the oxygen was reduced via the release of moisture and CO. Using CO2 in pyrolysis inhibited the generation of nitriles derivatives in POs, which are harmful to the environment. These results indicated that the application of CO2 to the thermal treatment of T-MFW could be feasible in energy production as well as environmental pollution control.

The removal of arsenic from solution through biochar-enhanced precipitation of calcium-arsenic derivatives

Arsenic (As) pollution remains a major threat to the quality of global soils and drinking water. The health effects of As pollution are often severe and have been largely reported across Asia and South America. This study investigated the possibility of using unmodified biochar derived from rice husk (RB) and aspen wood (WB) at 400 °C and 700 °C to enhance the precipitation of calcium/arsenic compounds for the removal of As(III) from solution. The approach was based on utilizing calcium to precipitate arsenic in solution and adding unmodified biochar to enhance the process. Using this approach, As(III) concentration in aqueous solution decreased by 58.1% when biochar was added, compared to 25.4% in the absence of biochar. Varying the pH from acidic to alkaline enabled an investigation into the pH dependent dynamics of the approach. Results indicated that significant precipitation was only possible at near neutral pH (i.e. pH = 6.5) where calcium arsenites (i.e. Ca(AsO₂)₂, and CaAsO₂OH•½H₂O) and arsenates (i.e. Ca₅(AsO₄)₃OH) were precipitated and deposited as aggregates in the pores of biochars. Arsenite was only slightly precipitated under acidic conditions (pH = 4.5) while no arsenite was precipitated under alkaline conditions (pH = 9.5). Arsenite desorption from wood biochar was lowest at pH 6.5 indicating that wood biochar was able to retain a large quantity of the precipitates formed at pH 6.5 compared to pH 4.5 and pH 9.5. Given that the removal of As(III) from solution is often challenging and that biochar modification invites additional cost, the study demonstrated that low cost unmodified biochar can be effective in enhancing the removal of As(III) from the environment through Ca-As precipitation.

Effects of sheep bone biochar on soil quality, maize growth, and fractionation and phytoavailability of Cd and Zn in a mining-contaminated soil

Biochar prepared from various feedstock materials has been utilized in recent years as a potential stabilizing agent for heavy metals in smelter-contaminated soils. However, the effectiveness of animal bone-derived biochar and its potential for the stabilization of contaminants remains unclear. In the present study, sheep bone-derived biochar (SB) was prepared at low (500 °C; SBL) and high temperatures (800 °C; SBH) and amended a smelter-contaminated soil at 2, 5, and 10% (w/w). The effects of SB on soil properties, bioavailable Zn and Cd and their geochemical fractions, bacterial community composition and activity, and the response of plant attributes (pigments and antioxidant activity) were assessed. Results showed that the SBH added at 10% (SBH₁₀) increased soil organic carbon, total nitrogen, and phosphorus, and also increased the oxidizable and residual Zn and Cd fractions at the expense of the bioavailable fractions. The SBH₁₀ lowered the Zn and Cd contents in maize roots (by 57 and 60%) and shoot (by 42 and 61%), respectively, compared to unamended control. Additionally, SBH₁₀ enhanced urease (98%) and phosphates (107%) activities, but reduced dehydrogenase (58%) and β-glucosidase (30%) activities. Regarding the effect of the pyrolysis temperature, SBH enhanced the activity of Acidobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Verrucomicrobia, Chlorobi, and Microgenomates, but reduced Actinobacteria and Parcubacteria in comparison to SBL. However, only the SBL₁₀ reduced the Proteobacteria community (by 9%). In conclusion, SB immobilized Zn and Cd in smelter-affected soils, enhanced the bacterial abundance and microbial function (urease, phosphates), and improved plant growth. However, validation of the results, obtained from the pot experiment, under field conditions is suggested.

Anchoring Al- and/or Mg-oxides to magnetic biochars for Co-uptake of arsenate and fluoride from water

The co-occurrence of arsenic and fluoride in the water environment has led to many health concerns for living beings. Simultaneous removal of such ions is crucial to the safety of water resources, and biochar has been extensively engaged to address this issue. Here four magnetic biochars (mBCs) including pristine magnetic biochar and three aluminum (Al) and/or magnesium (Mg) oxides-anchored magnetic biochar (i.e., Al-mBC, Mg-mBC, and MgAl-mBC) were prepared via a facile pyrolysis method and then comprehensively evaluated as adsorbents for enhanced co-uptake of arsenate (As^V) and fluoride (F^-) from synthetic water. The mBC shows a high specific surface area of 205 m² g^-1, which dropped to 116, 80, and 114 m² g^-1 upon the anchoring of Al, Mg, and Mg + Al, respectively. Our results suggest that the adsorption of either As^V or F^- is highly pH-dependent, and pH 4-6 is the optimal range for maximum adsorption. The adsorption isotherm data indicate that the MgAl-mBC adsorbent outranks all other mBCs for co-uptake of both As^V and F^-. The adsorption capacity maxima of MgAl-mBC are 34.45, and 21.59 mg g^-1 for As^V and F^-, respectively (pH = 5, T = 10 °C), also highly outstripping other biochars reported in the literature. The magnetic feature of these mBCs enables us to fast reclaim and regenerate the exhausted adsorbents by an external magnet and dilute NaOH. The Al- and Mg-anchored mBCs are expected to be used as highly efficient adsorbents for environmental remediation of waters contaminated by both As^V and F^-.

Competitive adsorption of pollutants from anodizing wastewaters to promote water reuse

Anodizing wastewater contains principally phosphate (PO₄^3-) anions according to previous studies, but with the purpose to promote water reuse in this type of industry, a complete characterization of wastewater was made to remove other anions and cations also present in significant concentration. Particularly, the adsorption of sodium (Na⁺), potassium (K⁺), fluoride (F^-), sulfate (SO₄^2-) and phosphate (PO₄^3-) was studied using different sorbents such as: coconut shell activated carbon, bone char, bituminous coal activated carbon, natural zeolite, silica, anionic and cationic exchange resins, a coated manganese-calcium zeolite, coconut shell activated carbon containing iron and iron hydroxide. All sorbents were characterized using FT-IR spectroscopy, potentiometric titration, nitrogen adsorption isotherms at 77 K, X-ray diffraction and SEM/EDX analysis to study the adsorption mechanism. The adsorption studies were performed in batch systems under constant agitation using both standard solutions of each ion and real anodizing wastewater. Results showed that, in general, the adsorption of all anions and cations is higher when mono-component standard solutions were used, since in the anodizing wastewater all species are competing for the active sites of the adsorbent. Na⁺ present in anodizing wastewater was efficiently adsorbed on coated manganese-calcium zeolite (20.55 mg/g) and natural zeolite (18.55 mg/g); while K⁺ was poorly adsorbed on all sorbents (less than 0.20 mg/g). Anions such as F^-, SO₄^2- and PO₄^3-, were better adsorbed on the anionic resin (0.17, 45.38 and 2.92 mg/g, respectively), the iron hydroxide (0.14, 7.96 and 2.87 mg/g, respectively) and the bone char (0.34, 8.71 and 0.27 mg/g, respectively). All these results suggest that adsorption is a promising tertiary treatment method to achieve water reuse in the anodizing industry.

Optimizing pyrolysis conditions for recycling pig bones into phosphate fertilizer

Selecting pyrolysis parameters for recycling P-rich and hazardous biowastes, such as bones, into fertilizers is still a challenge. Our objective was to improve pyrolysis procedures of pig bones for the production of P fertilizers. Bone chars were produced by pyrolysis at 400, 550, or 800 °C with no gas addition; 550 and 800 °C under N₂; 800 °C under steam flux, using calcination at 800 °C as control treatment. Synchrotron-based X-ray diffraction and X-ray absorption near edge structure spectroscopy at the P and Ca K- and L-edges showed that these bone chars were largely composed of hydroxyapatite. Hydroxyapatite crystallization was inhibited by pyrolysis conducted in the absence of oxygen at 400, 550, or 800 °C, either under no gas or under N₂ flux. The clogging of pores by lack of organic compounds removal was hypothesized to cause low surface area of 400 °C bone char, resulting in a fertilizer with citric-acid soluble P as low as calcination, while 550 and 800 °C bone chars obtained in absence of oxygen showed greater porosity, surface area, and citric acid-soluble P than steamed or calcined samples at 800 °C. Although extractable phosphate in water and neutral-ammonium-citrate showed trends comparable to those from citric acid, it was negligible for all heated materials. Since it is possible to produce bone chars with different chemical, physical and crystallographic properties by managing pyrolysis conditions, bone chars can be designed to increase their suitability as P fertilizers for different purposes, such as high solubility or slow P release.

Evaluation of Fluoride Adsorption Mechanism and Capacity of Different Types of Bone Char

The fluoride adsorption capacity of three types of bone char (BC), including cow BC (CBC), chicken BC (CKBC), and pig BC (PBC), was examined. At the optimum charring conditions (temperature and time), PBC had the highest hydroxyapatite (HAP) content (0.928 g-HAP/g-BC), while CBC had the highest specific surface area (103.11 m²/g-BC). CBC also had the maximum fluoride adsorption capacity (0.788 mg-F/g-HAP), suggesting that fluoride adsorption capacity depends more on the specific surface area of the BC than the HAP content. The adsorption data of CBC, CKBC, and PBC fit well with the pseudo-second-order model and the Langmuir isotherm. The maximum fluoride adsorption capacity of BC reached the maximum value when the solution had a pH of approximately 6.0. Lastly, the highest fluoride desorption occurred when the BCs were soaked in solutions with a pH higher than 11.0.

Bone-derived biochar improved soil quality and reduced Cd and Zn phytoavailability in a multi-metal contaminated mining soil

Reusing by-products such as cow bones in agriculture can be achieved thorough pyrolysis. The potential of bone-derived biochar as a promising material for metals immobilization in contaminated mining soils has not yet been sufficiently explored. Therefore, cow bones were used as biochar feedstock were pyrolyzed at 500 °C (CBL) and 800 °C (CBH) and. The two biochars were applied to a mine contaminated soil at 0 (control), 2.5, 5 and 10%, w/w, dosages; then, the soils were incubated and cultivated by maize in the greenhouse. Cadmium (Cd) and zinc (Zn) bioavailability and their sequentially extracted fractions (acid soluble, reducible, oxidizable, and residual fraction), soil microbial function, and plant health attributes were analyzed after maize harvesting. Bone-derived biochar enhanced the content of dissolved organic carbon (up to 74%), total nitrogen (up to 26%), and total phosphorus (up to 27%) in the soil and improved the plant growth up to 55%, as compared to the control. The addition of CBL altered the acid soluble fraction of both metals to the residual fraction and, thus, reduced the content of Zn (55 and 40%) and Cd (57 and 67%) in the maize roots and shoots, respectively as compared to the control. The CBL enhanced the β-glucosidase (51%) and alkaline phosphatase activities (71%) at the lower doses (2.5-5%) as compared to control, while the activities of these enzymes decreased with the higher application doses. Also, CBL improved the antioxidants activity and maize growth at the 2.5-5% application rate. However, the activity of the dehydrogenase significantly decreased (77%), particularly with CBH. We conclude that CBL, applied at 2.5-5% dose, can be utilized as a potential low cost and environmental friendly amendment for stabilization of toxic metals in contaminated mining soils and producing food/feed/biofuel crops with lower metal content.

Catalytic upgrade for pyrolysis of food waste in a bubbling fluidized-bed reactor

Biofuel production via pyrolysis has received increasing interest as a promising solution for utilization of now wasted food residue. In this study, the fast pyrolysis of mixed food waste (MFW) was performed in a bubbling fluidized-bed reactor. This was done under different operating conditions (reaction temperatures and carrier gas flow rate) that influence product distribution and bio-oil composition. The highest liquid yield (49.05 wt%) was observed at a pyrolysis temperature of 475 °C. It was also found that the quality of pyrolysis bio-oils (POs) could be improved using catalysts. The catalytic fast pyrolysis of MFW was studied to upgrade the pyrolysis vapor, using dolomite, red mud, and HZSM-5. The higher heating values (HHVs) of the catalytic pyrolysis bio-oils (CPOs) ranged between 30.47 and 35.69 MJ/kg, which are higher than the HHVs of non-catalytic pyrolysis bio-oils (27.69-31.58 MJ/kg). The major components of the bio-oils were fatty acids, N-containing compounds, and derivatives of phenol. The selectivity for bio-oil components varied depending on the catalysts. In the presence of the catalysts, the oxygen was removed from oxygenates via moisture, CO₂, and CO. The CPOs contained aliphatic hydrocarbons, polycyclic aromatic compounds (such as naphthalene), pyridine derivatives, and light oxygenates (cyclic alkenes and ketones).

Inorganic arsenic species removal from water using bone char: A detailed study on adsorption kinetic and isotherm models using error functions analysis

The removal of inorganic arsenic (As) species from water using bone char pyrolyzed at 900 °C was investigated. Results revealed that the Sips model resulted in the best As(III) experimental data fit, while As(V) data were best represented by the Langmuir model. The adsorption rate and mechanisms of both As species were investigated using kinetic and diffusional models, respectively. At low As(III) and As(V) concentrations of 0.5 and 2.5 mg/L, the removal was due to intra-particle interactions and pore diffusion following Pseudo-first-order kinetics. However, at higher concentrations of 5 and 10 mg/L, the pore diffusion mechanism was ineffective, and the adsorption was best described by Pseudo-second-order and Elovich models. The goodness of the fit of linearized and nonlinear forms of all models against experimental data was thoroughly tested using error function analysis. Nonlinear regressions produced lower error values, so they were utilized to calculate the parameters of the models. The changes in bone char surface chemistry were examined using FTIR and Energy-dispersive X-ray spectroscopy (EDS). Arsenic oxide and complexes with metals were the confirmed immobilized forms of As on the bone-char surface. To the authors' knowledge, this study is the first attempt at As(III) adsorption analysis using bone char.

Effective removal of excessive fluoride from aqueous environment using activated pods of Bauhinia variegata: Batch and dynamic analysis

In this study, a novel biosorbent is prepared from the pods of Bauhinia variegata is used for defluoridation of the fluoride contaminated water. It is an eco-friendly and economically feasible material. Comparison of adsorption capacity of Physically Treated Bauhinia (PTB) and Chemically Treated Bauhinia (CTB) are carried in this work. Characterization studies like SEM, EDS, FTIR, and XRD are executed to analyze surface morphology and functional groups in PTB and CTB. The experimental procedure was implemented in a batch process where the operating constraints such as dosage, pH, initial fluoride concentration, time, and temperature are varied to attain optimized efficiency. PTB and CTB yield an adsorption capacities of 10.90 mg/g and 15.45 mg/g respectively in the batch process. PTB adheres fluoride in monolayer formation whereas CTB forms multilayer adsorption. The adsorption process was described by the Pseudo first-order model to state the mechanism of physisorption. The negative values of thermodynamic parameters indicate spontaneity and favorable conditions for adsorption process. As CTB has a higher adsorption capacity than PTB, the batch study has been extended to column adsorption. Bed depth, initial fluoride concentration, and flow rate are the experimental variables used to acquire breakthrough curves. Simplified column models like Adam-Bohart, Thomas, and Yoon-Nelson models were analyzed. In column studies, Yoon-Nelson model fitted well in describing the process of adsorption. The maximum adsorption capacity acquired during the column process was found to be 1.176 mg/g with a bed depth of 5 cm and a flow rate of 5 ml/min. Thus, the innocuous and sustainable adsorbent is developed and serves as an excellent defluoridation agent.

Facile synthesis of chitosan-modified ZnO/ZnFe2O4 nanocomposites for effective remediation of groundwater fluoride

This study explores the possibility of developing an eco-friendly adsorbent for effective remediation of groundwater fluoride, a well-known health hazard affecting more than 25 nations on the various continents. A facile and milder approach has been adopted to synthesize chitosan-modified ZnO/ZnFe₂O₄ nanocomposites. The synthesized materials have been characterized by different spectroscopic, microscopic, and diffractometric techniques. X-ray photoelectron spectroscopy and X-ray diffraction studies have confirmed the formation of pure and highly crystalline ZnO/ZnFe₂O₄ nanocomposites. The presence of surface-adsorbed chitosan in the modified ZnO/ZnFe₂O₄ has been confirmed by FT-IR and thermogravimetric analysis. The results from microscopic and BET surface area analysis of ZnO/ZnFe₂O₄ nanocomposites indicated that chitosan plays a crucial role in modulating the surface morphology and surface properties of the nanocomposites. The nanocomposites exhibit excellent adsorption performance in the remediation of groundwater fluoride. Experimental conditions have been systematically designed to evaluate the optimum adsorption condition for fluoride, and the results have been analyzed with various non-linear models to describe the kinetics and isotherms of adsorption. The adsorption primarily follows Lagergren pseudo-first-order kinetics, and the Langmuir adsorption capacity is varied from 10.54 to 13.03 mg g^-1 over the temperature range 293-323 K. The thermodynamics study reveals that the adsorption process is endothermic and spontaneous. The mechanism of adsorption has been proposed based on the spectroscopic analysis of the fluoride-loaded adsorbent. The adsorption is non-specific in nature as co-existing anion can reduce its fluoride removal capacity. The effect of the co-existing anions on adsorption of fluoride follows the trend PO₄^3- > CO₃^2- > SO₄^2- > Cl^-. The adsorbent can be reused successfully for the 5th consecutive cycles of adsorption-desorption study. This study offers a very promising material for remediation of groundwater fluoride of affected areas.

Greenhouse Crop Residue and Its Derived Biochar: Potential as Adsorbent of Cobalt from Aqueous Solutions

This work is focused on the removal of cobalt from aqueous solutions using the greenhouse crop residue and biochars resulting from its pyrolysis at different temperatures, which have not been previously used for this purpose. This study aims to provide insights into the effect of pyrolysis temperature as a key parameter on the cobalt adsorption capacity of these materials. Firstly, the main physicochemical properties of greenhouse crop residue and its biochars prepared under different pyrolysis temperatures were characterized by elemental analysis and FT-IR, among others. Then, the cobalt adsorption capacity of materials was evaluated in batch systems. The best results were obtained for the biochar prepared by pyrolysis at 450 °C (adsorption capacity of 28 mg/g). Generally, the adsorption capacity of the materials increased with pyrolysis temperature. However, when the treatment temperature was increased up to 550 °C, a biochar with worse properties and behavior than cobalt adsorbent was produced. Rather than surface area and other physical properties, functional groups were found to influence cobalt adsorption onto the prepared materials. The adsorption kinetics showed that the adsorption followed pseudo-second-order kinetics model. The obtained equilibrium data were fitted better by the Langmuir model rather than the Freundlich model. Finally, decomposition of loaded-materials was analyzed to assess their possible recycling as fuel materials. The study suggested that greenhouse crop residue can be used as a low-cost alternative adsorbent for cobalt removal from aqueous solutions.