Facile synthesis of hydroxyapatite/yeast biomass composites and their adsorption behaviors for lead (II)

Synthesis of novel magnetic hydroxyapatite-biomass nanocomposite for arsenic and fluoride adsorption

A magnetic nanocomposite of hydroxyapatite and biomass (HAp-CM) was synthesized through a combined ultrasonic and hydrothermal method, aiming for efficient adsorption of arsenic (As) and fluoride (F-) from drinking water in natural environments. The characterization of HAp-CM was carried out using TG, FTIR, XRD, SEM, SEM-EDS, and TEM techniques, along with the determination of pHpzc charge. FTIR analysis suggested that coordinating links are the main interactions that allow the formation of the nanocomposite. XRD data indicated that the crystalline structure of the constituent materials remained unaffected during the formation of HAp-CM. SEM-EDS analysis revelated a Ca/P molar ratio of 1.78. Adsorption assays conducted in batches demonstrated that As and F- followed a PSO kinetic model. Furthermore, As adsorption fitting well to the Langmuir model, while F- adsorption could be explained by both Langmuir and Freundlich models. The maximum adsorption capacity of HAp-CM was found to be 5.0 mg g-1 for As and 10.2 mg g-1 for F-. The influence of sorbent dosage, pH, and the presence of coexisting species on adsorption capacity was explored. The pH significantly affected the nanocomposite's efficiency in removing both pollutants. The presence of various coexisting species had different effects on F- removal efficiency, while As adsorption efficiency was generally enhanced, except in the case of PO43-. The competitive adsorption between F- and As on HAp-CM was also examined. The achieved results demonstrate that HAp-CM has great potential for use in a natural environment, particularly in groundwater remediation as a preliminary treatment for water consumption.

Hydroxyapatite and its composite in heavy metal decontamination: Adsorption mechanisms, challenges, and future perspective

Nanohydroxyapatite (n-HAP), recognized by its peculiar crystal architecture and distinctive attributes showcased the underlying potential in adsorbing heavy metal ions (HMI). In this paper, the intrinsic mechanism of HMI adsorption by n-HAP was first revealed. Subsequently, the selectivity and competitiveness of n-HAP for HMI in a variety of environments containing various interferences from cations, anions, and organic molecules are elucidated. Next, n-HAP was further categorized according to its morphological dimensions, and its adsorption properties and intrinsic mechanisms were investigated based on these different morphologies. It was shown that although n-HAP has excellent adsorption capacity and cost-effectiveness, its application is often challenging to realize due to its inherent fragility and agglomeration, the technical problems required for its handling, and the difficulty of recycling. Finally, to address these issues, this paper discusses the tendency of n-HAP and its hybridized/modified materials to adsorb HMI as well as the limitations of their applications. By summarizing the limitations and future directions of hybridization/modification HAP in the field of HMI contamination abatement, this paper provides insightful perspectives for its gradual improvement and rational application.

Exploration of Converting Food Waste into Value-Added Products via Insect Pretreatment-Assisted Hydrothermal Catalysis

The environmental burden of food waste (FW) disposal coupled with natural resource scarcity has aroused interest in FW valorization; however, transforming FW into valuable products remains a challenge because of its heterogeneous nature. In this study, a two-stage method involving black soldier fly (BSF)-based insect pretreatment and subsequent hydrothermal catalysis over a single-atom cerium-incorporated hydroxyapatite (Ce-HAP) was explored to convert FW into high added-value furfurals (furfural and 5-hydroxymethylfurfural). FW consisting of cereal, vegetables, meat, eggs, oil, and salt was initially degraded by BSF larvae to generate homogeneous BSF biomass, and then, crucial parameters impacting the conversion of BSF biomass into furfurals were investigated. Under the optimized conditions, 9.3 wt % yield of furfurals was attained, and repeated trials confirmed the recyclability of Ce-HAP. It was proved that the revenue of furfural production from FW by this two-stage method ranged from 3.14 to 584.4 USD/tonne. This study provides a potential technical orientation for FW resource utilization.

Biofabricated yeast: super-soldier for detoxification of heavy metals

The advances in nanotechnology have shown enormous impacts in environmental technology as a potent weapon for degradation of toxic organic pollutants and detoxification of heavy metals. It is either by in-situ or ex-situ adaptive strategies. Mycoremediation of environmental pollutants has been a success story of the past decade, by employing the wide arsenal of biological capabilities of fungi. Recently, the proficiency and uniqueness of yeast cell surface alterations have encouraged the generation of engineered yeast cells as dye degraders, heavy metal reduction and its recovery, and also as detoxifiers of various hazardous xenobiotic compounds. As a step forward, recent trends in research are towards developing biologically engineered living materials as potent, biocompatible and reusable hybrid nanomaterials. They include chitosan-yeast nanofibers, nanomats, nanopaper, biosilica hybrids, and TiO₂-yeast nanocomposites. The nano-hybrid materials contribute significantly as supportive stabilizer, and entrappers, which enhances the biofabricated yeast cells' functionality. This field serves as an eco-friendly cutting-edge cocktail research area. In this review, we highlight recent research on biofabricated yeast cells and yeast-based biofabricated molecules, as potent heavy metals, toxic chemical detoxifiers, and their probable mechanistic properties with future application perspectives.

Amine-bilayer-functionalized cellulose-chitosan composite hydrogel for the efficient uptake of hazardous metal cations and catalysis in polluted water

Herein, we represent a novel ecofriendly bilayer-amine group incorporated microcrystalline cellulose (MCC)/chitosan (CS) hydrogel, fabricated via integrating polydopamine (PDA) and polyethyleneimine (PEI) for reliable and effective extraction of copper (Cu²⁺), zinc (Zn²⁺), and nickel (Ni²⁺) ions from effluents. Owing to abundant adsorptive sites, the MCC-PDA-PEI/CS-PDA-PEI hydrogel showed excellent Cu²⁺, Zn²⁺, and Ni²⁺ adsorbabilities of ~434.8, ~277.7, and ~261.8 mg/g, respectively, in a single-ion adsorption system with the adsorption kinetics and isotherm complied with pseudo-second-order and Langmuir models, respectively. In a multi-ion adsorption system, hydrogel removes mixed metal cations with slightly higher selectivity for Cu²⁺. In accordance with X-ray photoelectron and Fourier-transform-infrared spectrometric analyses, a plausible binding mechanism of metal cations on the as-prepared hydrogel was proposed by chelation between hydrogel functional groups and metal ions. In the repetitive adsorption/desorption experiments, the hydrogel retained >40% metal ion adsorption and desorption capacities after four cycles. Furthermore, the Cu²⁺-adsorbing hydrogel could serve as a support for the in situ development of Cu nanoparticles, which showed excellent catalytic performance as demonstrated by the transformation of 4-nitrophenol (4-NP) to 4-aminophenol. This work provides a novel ecofriendly, reusable, and highly-efficient adsorbent, as well as a biocatalyst for remediation of heavy metal cations and 4-NP polluted effluents.

Phenanthroline-based microporous organic materials for removal of Cu(II) from aqueous solution and reutilization of spent adsorbent as catalysts

Microporous organic polymers (MOPs) possessing large specific surface area with high stability are suitable adsorbent to remove contaminants from water, such as organic pollutant and heavy metal contaminants. Herein, a phenanthroline-based microporous organic polymer (Phen-MOP) has been synthesized through the coupling between benzene and 1,10-phenanthroline. The adsorption kinetics and thermodynamics were investigated. This Phen-MOP exhibited good adsorption efficiency for removal of Cu(II) from water with high structural stability and reusability. The maximum removal efficiency could reach to 98.47% at a Cu(II) concentration of 20 mg/L, pH = 7, 25 °C. It was found by investigating the adsorption isotherms that the maximum adsorption capacity Q_m was 128.53 mg/g. Interestingly, after the adsorption of Cu(II), the resulting Phen-MOP-Cu can serve as an efficient heterogeneous catalyst for the Ullmann-type reaction. The structure and composition of the Phen-MOP-Cu were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The results indicated that this catalyst possessed immense specific surface area, large pore volume and high stability. The catalyst was easily recyclable and did not significantly lose catalytic activity after being reused six times.

Hydroxyapatite-based adsorbents: Applications in sequestering heavy metals and dyes

Hydroxyapatite (HAp) is a calcium phosphate material that was used primarily in bone regeneration and repair as a result of its chemical similarity with bone. However, HAp has emerged as a very promising adsorbent for sequestering contaminants like heavy metals, dyes, hydrocarbons as well as other emerging pollutants from wastewater as a result of its versatility and encouraging adsorptive properties. Contaminants like heavy metals and dyes have been a major source of environmental concern. Research studies involving the use of HAp as adsorbents for the adsorptive treatment of heavy metal- and dye-contaminated wastewater have become increasingly popular due to its eco-friendliness, easy synthesis, unique adsorption properties etc. Various methods are available for the synthesis of HAp and its composites with some of these methods used in combination with other methods to obtain more efficient HAp-based adsorbents. In this work, the adsorptive removal of heavy metals and dyes by HAp and its composites was extensively reviewed as well as the parametric effects of process factors like contact time, solution pH, temperature, solute concentration etc on the adsorption process. Kinetic, thermodynamic, and isotherm models for elucidating the adsorption process were also considered. Generally, from the works reviewed, HAp-based adsorbents were found to be very effective for sequestering heavy metals and dyes from solution and thus presents a low-cost option for adsorptive wastewater treatment.

Zinc and cadmium adsorption from wastewater using hydroxyapatite synthesized from flue gas desulfurization waste

The purpose of this work is to produce an alternative cost-effective adsorbent to remove zinc and cadmium from wastewater using hydroxyapatite (HAP) synthesized with hydrothermal method from FGD (Flue gas desulfurization) waste generated by two different coal power plants. The effects of FGD type (Cayırhan and Orhaneli) and molar ratio (H₃PO₄/CaSO₄) (0.6-4.79) on HAP synthesis were investigated. Afterwards, effects of the adsorbent dose (1-2 g/L), heavy metal concentration (30, 40, 50 mg/L) and contact time (1, 2, 3, 4 h) on zinc and cadmium adsorption yield from synthetic wastewater using produced HAP were examined. FGD waste and synthesized FGD-HAP were characterized by X-Ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Brunauer-Emmett-Teller (BET) instruments. The zinc and cadmium concentration was studied by Inductively coupled plasma atomic emission spectroscopy (ICP-AES). Maximum zinc adsorption capacity of the Cayırhan FGD-HAP was 49.97 and 49.99 mg/L, Orhaneli FGD-HAP was 49.96 and 49.99 mg/L, for 1 g/L and 2 g/L adsorbent dose, respectively, for 50 mg/L heavy metal concentration and 4 h contact time. Maximum cadmium adsorption capacity of the Cayırhan FGD-HAP was 39.98 and 39.99 mg/L, Orhaneli FGD-HAP was 40 and 39.99 mg/L, for 1 g/L and 2 g/L adsorbent dose, respectively, for 40 mg/L heavy metal concentration and 4 h contact time. Adsorption yields were calculated between 98.53% and 100%. The adsorption data were well explained by a second-order kinetic model, and the Freundlich isotherm model fits the equilibrium data. The adsorption results demonstrated that FGD's waste is an effective source to synthesize HAP, which is used as an adsorbent for zinc and cadmium removal from wastewater due to high adsorption capacity.

Adsorption of Cu(II) by Poly-γ-glutamate/Apatite Nanoparticles

Poly-γ-glutamate/apatite (PGA-AP) nanoparticles were prepared by chemical coprecipitation method in the presence of various concentrations of poly-γ-glutamate (γ-PGA). Powder X-ray diffraction pattern and energy-dispersive spectroscopy revealed that the main crystal phase of PGA-AP was hydroxyapatite. The immobilization of γ-PGA on PGA-AP was confirmed by Fourier transform infrared spectroscopy and the relative amount of γ-PGA incorporation into PGA-AP was determined by thermal gravimetric analysis. Dynamic light scattering measurements indicated that the particle size of PGA-AP nanoparticles increased remarkably with the decrease of γ-PGA content. The adsorption of aqueous Cu(II) onto the PGA-AP nanoparticles was investigated in batch experiments with varying contact time, solution pH and temperature. Results illustrated that the adsorption of Cu(II) was very rapid during the initial adsorption period. The adsorption capacity of PGA-AP nanoparticles for Cu(II) was increased with the increase in the γ-PGA content, solution pH and temperature. At a pH of 6 and 60 °C, a higher equilibrium adsorption capacity of about 74.80 mg/g was obtained. The kinetic studies indicated that Cu(II) adsorption onto PGA-AP nanoparticles obeyed well the pseudo-second order model. The Langmuir isotherm model was fitted well to the adsorption equilibrium data. The results indicated that the adsorption behavior of PGA-AP nanoparticles for Cu(II) was mainly a monolayer chemical adsorption process. The maximum adsorption capacity of PGA-AP nanoparticles was estimated to be 78.99 mg/g.

Microwave-assisted preparation of manganese dioxide modified activated carbon for adsorption of lead ions

In this study, manganese dioxide was evenly distributed on the surface of activated carbon (AC), and the porous structure of AC and the surface functional groups of manganese dioxide were used to adsorb the heavy metal ion Pb(II). The advantages of microwave heating are fast heating and high selectivity. The mole ratio control of the AC and MnO₂ in 1:0.1, microwave heating to 800 °C, heat preservation for 30 min. The maximum adsorption capacity of the MnO₂-AC prepared by this method on Pb(II) can reach 664 mg/L at pH = 6. It can be observed by scanning electron microscope (SEM) that manganese dioxide particles are dispersed evenly on the surface and pore diameter of AC, and there is almost no agglomeration. The specific surface area was 752.8 m²/g, and the micropore area was 483.9 m²/g. The adsorption mechanism was explored through adsorption isotherm, adsorption kinetics, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). It is speculated that the adsorption mechanism includes electrostatic interaction and specific adsorption, indicating that lead ions enter into the void of manganese dioxide and form spherical complexes. The results showed that the adsorption behavior of Pb(II) by MnO₂-AC was consistent with the Langmuir adsorption model, the quasi-second-order kinetic model, and the particle internal diffusion model.

A novel lead-ion-imprinted magnetic biosorbent: preparation, optimization and characterization

A novel biological material with high adsorption capacity and good selectivity for Pb²⁺ was synthesized. Response surface methodology was utilized for the optimization of the variables during the synthesis. The synthesized biosorbent was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The optimized preparation condition for lead-ion-imprinted magnetic biosorbent (Pb(II)-IMB) was obtained (0.19 g chitosan (CTS), 0.43 g magnetic Fe₃O₄ and 2.11 mL/gCTS of epichlorohydrin). The highest value for the removal of lead ion was estimated to be 86.85%, with an absorption capacity of 69.48 mg/g. The characterization results indicated that Pb(II)-IMB was rich in adsorbable groups to adsorb metal ions. Because of the magnetic property of the synthesized products, it can be separated from the water easily. The relative selectivity coefficients of Pb(II)-IMB for Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Ni(II) were 2.32, 2.20 and 2.05 times higher than the non-imprinted magnetic biosorbent, respectively. Pb(II)-IMB could be reused at least five times with only ∼13% loss. These results suggested that Pb(II)-IMB was a new, efficient and low-cost material for removing Pb(II) from wastewater.

A multi-functional minimally-disruptive portable electrochemical system based on yeast/Co3O4/Au/SPEs for blood lead (II) measurement

A minimally-disruptive portable electrochemical system is constructed by combining a hand-held syringe as reservoir with disposable screen-printed electrodes (SPEs) modified with a simple and efficient yeast/Co₃O₄/Au material for lead determination by a square-wave voltammetry (SWV) method. Not only can it preserve the operation and advantages of the conventional electrochemical procedure, but it also integrates sampling, filtering and analysis to make the determination of lead convenient and effective at higher and lower concentration levels. This is the first report of a microbial biosensor based on active yeast crosslinked to Co₃O₄/Au particles using glutaraldehyde as the crosslinking agent. The determination process is simplified by introducing a fiber filter and takes only 150 s with the developed system, which illustrates its simplicity, speed and detection accuracy. Also, the design shows a wide log-linear dynamic range (LDR) from 10^-8 to 10^-14 g·L^-1, with a limit of detection (LOD) of 3.45 × 10^-15 g·L^-1 (S/N = 3). Additionally, the proposed system was used to determine lead in blood samples, which demonstrated the potential of this biosensor for use in practical applications. Furthermore, this study provides a basis for the development of microscale blood devices for lead measurement.

Facile low-temperature one-step synthesis of pomelo peel biochar under air atmosphere and its adsorption behaviors for Ag(I) and Pb(II)

This study prepared a novel low-cost surface functionalized carbon adsorbent (PPC) from biomass waste (pomelo peel) through a facile low-temperature (250 °C) one-step method under regular air atmosphere. The adsorption performance and mechanism of the carbon material for Ag(I) and Pb(II) were investigated by a range of sorption experiments and characterizations including SEM, EDX, XRD and FTIR. Sorption experimental results suggested that PPC had high adsorption capacities of 137.4 and 88.7 mg/g for Ag(I) and Pb(II), respectively, with adsorbent dosage of 2 g/L at unadjusted solution pH and room temperature (23 ± 1 °C). The characterization results indicated high-efficiency removal of the heavy metals by PPC was attributed to the strong chemical adsorption involving that Ag(I) ions were reduced as metallic Ag particles by oxygenic functional groups and Pb(II) ions were precipitated as Pb₅(PO₄)₃OH crystals by phosphorous functional groups on the carbon surfaces. This study provides the possibility of synthesis high-efficient adsorbent using economic and environmental-friendly approach with low energy consumption.

Rapid removal of Pb2+ from aqueous solution by phosphate-modified baker's yeast

Phosphate-modified baker's yeast (PMBY) was prepared, and used as a novel bio-sorbent for the adsorption of Pb2+ from aqueous solution. The influencing factors, absorption isotherms, kinetics, and mechanism were investigated. The scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) characterization and elemental analysis of PMBY showed that phosphate groups were successfully grafted onto the surface of yeast. The kinetic studies suggested that the adsorption process followed a pseudo-second-order chemisorption. The adsorption process of Pb2+ using PMBY was spontaneous and endothermic. Furthermore, the adsorption of Pb2+ on PMBY can rapidly achieve adsorption equilibrium (in just 3 min), and the maximum adsorption capacity of Pb2+ on PMBY was found to be 92 mg g-1 at 30 °C, which was about 3 times that of the pristine baker's yeast. The suggested mechanism for Pb2+ adsorption on PMBY was based upon ion-exchange, electrostatic interaction and chelation between the phosphate groups and Pb2+. However, compared with the pristine baker's yeast, the higher capacity and rapid adsorption of PMBY for Pb2+ was mainly due to the chelation and electrostatic interactions between the phosphate groups and Pb2+. In addition, the regeneration experiments indicated that the PMBY was easily recovered through desorption in 0.01 M HCl, and that PMBY still exhibited 90.77% of the original adsorption capacity for Pb2+ after five regeneration cycles. These results showed the excellent regeneration capability of PMBY for Pb2+ adsorption. PMBY has shown significant potential for the removal of heavy metals from aqueous solution due to its rapid adsorption, high-capacity and facile preparation.