Bacterial nanocellulose-clay film as an eco-friendly sorbent for superior pollutants removal from aqueous solutions.

The persistent water treatment and separation challenge necessitates innovative and sustainable advances to tackle conventional and emerging contaminants in the aquatic environment effectively. Therefore, a unique three-dimensional (3D) network composite film (BNC-KC) comprised of bacterial nanocellulose (BNC) incorporated nano-kaolinite clay particles (KC) was successfully synthesized via an in-situ approach. The microscopic characterization of BNC-KC revealed an effective integration of KC within the 3D matrix of BNC. The investigated mechanical properties of BNC-KC demonstrated a better performance compared to BNC. Thereafter, the sorption performance of BNC-KC films towards basic blue 9 dye (Bb9) and norfloxacin (NFX) antibiotic from water was investigated. The maximum sorption capacities of BNC-KC for Bb9 and NFX were 127.64 and 101.68 mg/g, respectively. Mechanistic studies showed that electrostatic interactions, multi-layered sorption, and 3D structure are pivotal in the NFX/Bb9 sorption process. The intricate architecture of BNC-KC effectively traps molecules within the interlayer spaces, significantly increasing sorption efficiency. The distinctive structural configuration of BNC-KC films effectively addressed the challenges of post-water treatment separation while concurrently mitigating waste generation. The environmental evaluation, engineering, and economic feasibility of BNC-KC are also discussed. The cost estimation assessment of BNC-KC revealed the potential to remove NFX and Bb9 from water at an economically viable cost.

The synergistic effect of typical chiral organic acids and solution chemistry conditions on the transport of 2-arylpropionic acid chiral derivatives in porous media.

The hazards of man-made chiral compounds are of great public concern, with reports of worrying stereoselective compounds and an urgent need to assess their transport. This study evaluated the transport of 2-arylpropionic acid derivatives enantiomers (2-APA) in porous media under a variety of solution chemistry conditions via column packing assays. The results revealed the introduction of Malic acid (MA) enantiomers enhanced the mobility of 2-APA enantiomers, but the enhancement effect was different for different 2-APA enantiomers. Batch sorption experiments confirmed that the MA enantiomers occupied the sorption site of the quartz sand, thus reducing the deposition of the 2-APA enantiomer. Homo- or heterochirality between 2-APA and MA dominates the transport of 2-APA enantiomers, with homochirality between them triggering stronger retention and vice versa. Further evaluating the effect of solution chemistry conditions on the transport of 2-APA enantiomers, increased ionic strength attenuated the mobility of 2-APA enantiomers, whereas introduced coexisting cations enhanced the retention of 2-APA enantiomers in the column. The redundancy analyses corroborated these solution chemistry conditions were negatively correlated with the transport of 2-APA enantiomers. The coupling of pH and these conditions reveals electrostatic forces dominate the transport behavior and stereoselective interactions of 2-APA enantiomers. Distinguishing the transport of enantiomeric pair helps to understand the difference in stereoselectivity of enantiomers and promises to remove the more hazardous one.

Optimizing bone and biomass co-torrefaction parameters: High-performance arsenic removal from wastewater via co-torrefied bone char.

This study aimed to investigate bone char's physicochemical transformations through co-torrefaction and co-pyrolysis processes with biomass. Additionally, it aimed to analyze the carbon sequestration process during co-torrefaction of bone and biomass and optimize the process parameters of co-torrefaction. Finally, the study sought to evaluate the arsenic sorption capacity of both torrefied and co-torrefied bone char. Bone and biomass co-torrefaction was conducted at 175 °C-300 °C. An orthogonal array of Taguchi techniques and artificial neural networks (ANN) were employed to investigate the influence of various torrefaction parameters on carbon dioxide sequestration within torrefied bone char. A co-torrefied bone char, torrefied at a reaction temperature of 300 °C, a heating rate of 15 °C·min-1, and mixed with 5 g m of biomass (wood dust), was selected for the arsenic (III) sorption experiment due to its elevated carbonate content. The results revealed a higher carbonate fraction (21%) in co-torrefied bone char at 300 °C compared to co-pyrolyzed bone char (500-700 °C). Taguchi and artificial neural network (ANN) analyses indicated that the relative impact of process factors on carbonate substitution in bone char followed the order of co-torrefaction temperature (38.8%) > heating rate (31.06%) > addition of wood biomass (30.1%). Co-torrefied bone chars at 300 °C exhibited a sorption capacity of approximately 3 mg g-1, surpassing values observed for pyrolyzed bone chars at 900 °C in the literature. The findings suggest that co-torrefied bone char could serve effectively as a sorbent in filters for wastewater treatment and potentially fulfill roles such as a remediation agent, pH stabilizer, or valuable source of biofertilizer in agricultural applications.

Using the benzenepolycarboxylic acid (BPCA) method to assess activated biochars and their PFAS sorption abilities.

Activated carbon (AC) has important industrial and environmental applications as it has excellent abilities to sorb contaminants such as per- and polyfluoroalkyl substances (PFAS). Current research aims to develop activated biochars (AB) from renewable biomass to replace AC that is produced from fossil feedstock. Both AC and AB are primarily comprised of condensed aromatic carbon (ConAC), the component that is the focus of this study. ConAC is characterized to determine its relationship with biochar activation conditions and PFAS sorption, which are understudied at present. Benzenepolycarboxylic acid (BPCA) markers for ConAC were quantified in steam-activated biochars (AB-Steam) and carbon dioxide-activated biochars (AB-CO2) prepared from waste timber at different temperatures (800, 850, 900 °C) and molar ratios of feedstock-carbon:steam (0.50 - 1.25). A non-activated biochar was also included as a reference. ConAC relative to total organic carbon content was higher in AB-Steam than in AB-CO2 (92 ± 2 % vs. 81 ± 11%). The ratio of benzenehexa- (B6CA) to benzenepentacarboxylic (B5CA) acids revealed that AB-Steam also had larger ConAC clusters than AB-CO2. These findings provide novel evidence that steam activation is more effective than CO2 activation in creating ConAC. To assess how ConAC impacts AB sorption abilities, AB-Steam were used to remediate PFAS from contaminated soils. The observed strong correlations between ConAC content and sorption of long-chain PFAS suggest the importance of hydrophobic interactions between PFAS tails and ConAC. Poor correlations for short-chain PFAS, on the other hand, indicated the existence of electrostatic repulsion interactions between PFAS head groups and ConAC. Collectively, these results explain the great ability of AB-Steam to sorb PFAS from contaminated soils (up to 100% remediation). More broadly, this work demonstrates that the BPCA method can be a valuable tool to assess the quality of biochars and other carbonaceous sorbents in relation to their production conditions or contaminant sorption abilities.

Comparison of Adsorption Performance of Biochar Derived from Urban Biowaste Materials for Removal of Heavy Metals.

This study investigated the adsorption performance of biochar produced from different types of urban biowaste material viz., sugarcane bagasse (SB), brinjal stem (BS), and citrus peel (CP) for removal of heavy metal ions (Pb, Cu, Cr, and Cd) from aqueous solution. The effects of biowaste material, dosage of biochar, solution pH, and initial concentration of heavy metal ions and isotherm models were performed to understand the possible adsorption mechanisms. The results showed that the biochar derived from BS and SB removes Cu (99.94%), Cr (99.57%), and Cd (99.77%) whereas biochar derived from CP removes Pb (99.59%) and Cu (99.90%) more efficiently from the aqueous solution. Biochar derived from BS showed maximum adsorption capacity for Cu (246.31 mg g-1), Pb (183.15 mg g-1), and Cr (71.89 mg g-1) while the biochar derived from CP showed highest for Cd (15.46 mg g-1). Moreover, biochar derived from BS and SB has more polar functional groups and less hydrophobicity than the biochar derived from CP. This study reveals that solution pH and biochar doses play a major role in removal of heavy metal ions from aqueous solution. The results of Langmuir model fitted well for Pb and Cu while the Freundlich model for Cr and Cd. Our study concludes that the biochar derived from different biowaste materials adsorbs heavy metal ions majorly through surface complexation and precipitation processes. The results of this study will be very useful in selecting the effective urban biowaste material for making biochar for heavy metal removal from the aqueous environment.

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.

Microplastic-Assisted Removal of Phosphorus and Ammonium Using Date Palm Waste Derived Biochar.

Microplastics (MPs) are emerging environmental pollutants worldwide, posing potential health risks. Moreover, MPs may act as vectors for other contaminants and affect their fate, transport, and deposition in the environment. Therefore, efficient and economical techniques are needed for the removal of contemporary MPs and contaminants from the environment. The present research study investigated the sorption of phosphorus (P) and ammonium (NH4+) onto date palm waste-derived biochar (BC) from an aqueous solution in the presence of polyamide (PA) and polyethylene (PE) MPs. The BC was prepared at 600 °C, characterized for physio-chemical properties, and applied for P and NH4+ removal via isotherm and kinetic sorption trials. The results of the sorption trials demonstrated the highest removal of NH4+ and P was obtained at neutral pH 7. The highest P sorption (93.23 mg g-1) by BC was recorded in the presence of PA, while the highest NH4+ sorption (103.76 mg g-1) was found with co-occurring PE in an aqueous solution. Sorption isotherm and kinetics models revealed that P and NH4+ removal by MP-amended BC followed chemisorption, electrostatic interaction, precipitation, diffusion, and ion exchange mechanisms. Overall, co-existing PA enhanced the removal of P and NH4+ by 66% and 7.7%, respectively, while co-existing PE increased the removal of P and NH4+ by 55% and 30%, respectively, through the tested BC. Our findings suggested that converting date palm waste into BC could be used as a competent and economical approach to removing P and NH4+ from contaminated water. Furthermore, microplastics such as PE and PA could assist in the removal of P and NH4+ from contaminated water using BC.

Phosphorus-modified bone chars with developed porosity for efficient removal of Pb(II), Cu(II), and Cd(II).

Guided by the concept of treating the wastes with wastes, the efficient use of bone residuals as separation materials is worthy of study. Since bone chars (BCs) are composed of hydroxyapatite and carbon matrix, it is desired to extend the carbon component with improved pore structure and abundant modified groups further, which is favorable to capture metal ions. In this work, phosphorus-modified BCs (PBCs) were fabricated by pretreating bone residuals with phytic acid, achieving improved surface areas (208.7-517.6 m2/g, 37.9-8.2-fold of enhancement) and abundant surface phosphorus contents (5.63-7.54 at.%, 2.8-5.8-fold of enhancement) than BCs. PBCs could adsorb heavy metals with fast kinetics (10.0 h) and excellent maximum capacities (463.9, 156.5, and 80.9 mg/g for Pb(II), Cu(II), and Cd(II)). Spectroscopic results demonstrated that the formation of precipitation was crucial for the enrichment of Pb(II). Moreover, the coordination with functional groups (O-/reductive N-species), the cation exchange with inorganic Ca2+, the electrostatic attraction with deprotonated O-, and the cation-π coordination should also be considered for the sorption. Our study facilitated the application of activated bone wastes as a promising candidate to remediate aquatic heavy metals.

Unravelling the Water Adsorption Mechanism in Hierarchical MOFs: Insights from In Situ Positron Annihilation Lifetime Studies.

Atmospheric water harvesting with metal-organic frameworks (MOFs) is a new technology providing a clean, long-term water supply in arid areas. In-situ positron annihilation lifetime spectroscopy (PALS) is proposed as a valid methodology for the mechanistic understanding of water sorption in MOFs and the selection of prospective candidates for desired applications. DUT-67-Zr and DUT-67-Hf frameworks are used as model systems for method validation because of their hierarchical pore structure, high adsorption capacity, and chemical stability. Both frameworks are characterized using complementary techniques, such as nitrogen (77 K) and water vapor (298 K) physisorption, SEM, and PXRD. DUT-67-Zr and DUT-67-Hf are investigated by PALS upon exposure to humidity for the first time, demonstrating the stepwise pore filling mechanism by water molecules for both MOFs. In addition to exploring the potential of PALS as a tool for probing MOFs during in situ water loading, this work offers perspectives on the design and use of MOFs for water harvesting.

Production of MgFe2O4/activated carbons derived from a harmful grass Cynodon dactylon and their utilization for ciprofloxacin removal.

Cynodon dactylon, an invasive species, exhibits its robust adaptability, reproduction and nutrient regime against the local species. Taking advantage of this harmful grass as a raw precursor to produce valuable materials for wastewater treatment has paid much attention. Herein, we report on the fabrication of Cynodom dactylon derived MgFe2O4@AC with a main goal of effective removal of ciprofloxacin antibiotic from water. Our findings showed that MgFe2O4@ACK1 composites attained mesoporous textures, high specific surface areas (884.3-991.6 m2 g-1), and MgFe2O4-20%@ACK1 was the most effective with a very high removal efficiency of 96.7%. The Elovich model was suitable for describing the kinetic of adsorption with (Radj)2 of 0.9988. Meanwhile, the isotherm data obeyed the Langmuir model corresponding to (Radj)2 of 0.9993. Qmax value of MgFe2O4-20%@ACK1 was determined at 211.67 mg g-1. The proposed adsorption mechanism primarily comprises five routes as follows, (i) pore-filling, (ii) π-π interaction, (iii) electrostatic interaction, (iv) hydrogen bonding, and (v) hydrophobic interaction. MgFe2O4-20%@ACK1 adsorbent could reuse with three cycles. We recommend that MgFe2O4/ACs derived from Cynodom dactylon could be high-efficiency adsorbents for the elimination of antibiotics.

Study on adsorption of ammonia nitrogen by sodium-modified kaolin at calcination temperature.

Natural kaolin (NK) is not used as a material for removal of ammonia nitrogen in wastewater because of its low ammonia adsorption capacity. In this study, sodium-modified kaolin adsorbent (NaCK) with high ammonia nitrogen adsorption capacity was prepared by NaOH modification of calcined NK, which was developed to address this problem. The adsorption properties were evaluated by batch static adsorption test. The results showed that when the initial concentration of ammonia nitrogen was 10 mg/L, pH = 8, and dosage of adsorbent was 1 g/L, the adsorption capacity of NaCK-600 for ammonia nitrogen was the best, reaching 6.23 mg/g, which was 34.6 times higher than that of NK (0.18 mg/g). Batch static adsorption test combined with adsorption kinetics, adsorption isothermal, and characteristic data showed that NaCK prepared at different temperatures had different adsorption mechanisms. Batch static adsorption test data of NaCK-600 was in good agreement with the pseudo-second-order model and Langmuir model, and the main mechanism of its adsorption of ammonia nitrogen was the ion exchange of NH4+ and Na+ in NaCK. After the third cycle, the removal rate of NaCK-600 was still up to 76.44%, which indicates that NaCK-600 has considerable potential for removal of ammonia nitrogen in wastewater and provides a new way for the application of kaolin in removal of ammonia nitrogen.

Extended Rate Constants Distribution (RCD) Model for Sorption in Heterogeneous Systems: 4. Kinetics of Metal Ions Sorption in the Presence of Complexing Agents-Application to Cu(II) Sorption on Polyethyleneimine Cryogel from Acetate and Tartrate Solutions.

Here, we report a new version of the extended Rate Constants Distribution (RCD) model for metal ion sorption, which includes complex-formation equilibria. With the RCD-complex model, one can predict sorbent performance in the presence of complexing agents using data on metal ion sorption from ligand-free solutions and a set of coefficients for sorption rate constants of different ionic species. The RCD-complex model was applied to breakthrough curves of Cu(II) sorption from acetate and tartrate solutions on polyethyleneimine (PEI) monolith cryogel at different flow rates and ionic speciation. We have shown that, despite the lower stability of Cu(II)-acetate complex, at high flow rates, acetate has a more pronounced negative effect on sorption kinetics than tartrate. The RCD model was successfully used to predict the shape of the breakthrough curves at an arbitrary acetate concentration but failed to predict Cu(II) sorption from tartrate solutions in a broad range of ligand concentrations. Since a twofold increase in sorption capacity was observed at low tartrate concentrations, the latter fact was related to an alteration in the sorption mechanism of Cu(II)-ions, which depended on Cu(II) ionic speciation. The obtained results emphasize the importance of information about sorption kinetics of different ionic forms for the optimization of sorption filter performance in the presence of complexing agents.

Rigidity and Flexibility: Unraveling the Role of Fulvic Acid in Uranyl Sorption on Graphene Oxide Using Molecular Dynamics Simulations.

Using molecular dynamics simulations, this work targets a molecular understanding on the rigidity and flexibility of fulvic acid (FA) in uranyl sorption on graphene oxide (GO). The simulations demonstrated that both rigid Wang's FA (WFA) and flexible Suwannee River FA (SRFA) can provide multiple sites to cooperate with GO for uranyl sorption and act as "bridges" to connect uranyl and GO to form GO-FA-U (type B) ternary surface complexes. The presence of flexible SRFA was more beneficial to uranyl sorption on GO. The interactions of WFA and SRFA with uranyl were primarily driven by electrostatics, and the electrostatic interaction of SRFA-uranyl was significantly stronger owing to the formation of more complexes. The flexible SRFA could markedly enhance the bonding strength of uranyl with GO by folding itself to provide more sites to coordinate with uranyl. The rigid WFAs tended to be adsorbed on the GO surface in parallel due to π-π interactions, whereas the flexible SRFAs took more slant configurations resulting from intermolecular hydrogen bonds. This work provides new insights into the sorption dynamics, structure, and mechanism and addresses the effect of molecular rigidity and flexibility, with great significance for FA-based remediation strategies of uranium-contaminated sites.

Sorption study of long-lived 94Nb on laterite: Effects of physicochemical parameters on sorption.

Zr-Nb alloy is used as the pressure tube in pressurized heavy water reactors (PHWR). Prolonged neutron irradiation of the pressure tubes leads to the formation of a long-lived radioisotope 94Nb. Thus, the discharged pressure tubes possess huge 94Nb activity which persists for a prolonged period.If these discharged pressure tubes come in contact with ground water, 94Nb isotope may leach and migrate and this can lead to a long-term radiological impact in the environment.In the present study, we have explored the capability of laterite as a filler material for the containment and retarding the migration of 94Nb. In this regard, detailed characterization of the laterite soil was carried out using energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), fourier transform infra-red spectrometry (FTIR), total cation exchange capacity determination, zeta potential measurement and thermogravimetric analysis (TGA). The sorption study of 94Nb on laterite was carried and the effects of different physico-chemical parameters like pH, ionic strength, temperature and equilibration time were evaluated. Ionic strength, temperature and time dependent sorption studies assist to explore the probable sorption mechanism of 94Nb on laterite, which helps in understanding the migration behaviour of 94Nb in natural aquatic environment. This study suggests that laterite is a promising material in containment of 94Nb isotope owing to its good cation exchange behaviour in the acidic medium and ability to form surface complex in the neutral medium.

A systematic review on distribution, sources and sorption of perfluoroalkyl acids (PFAAs) in soil and their plant uptake.

Perfluoroalkyl acids (PFAAs) are ubiquitous in environment, which have attracted increasing concerns in recent years. This study collected the data on PFAAs concentrations in 1042 soil samples from 15 countries and comprehensively reviewed the spatial distribution, sources, sorption mechanisms of PFAAs in soil and their plant uptake. PFAAs are widely detected in soils from many countries worldwide and their distribution is related to the emission of the fluorine-containing organic industry. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are found to be the predominant PFAAs in soil. Industrial emission is the main source of PFAAs contributing 49.9% of the total concentrations of PFAAs (Æ© PFAAs) in soil, followed by activated sludge treated by wastewater treatment plants (WWTPs) (19.9%) and irrigation of effluents from WWTPs, usage of aqueous film-forming foam (AFFFs) and leaching of leachate from landfill (30.2%). The adsorption of PFAAs by soil is mainly influenced by soil pH, ionic strength, soil organic matter and minerals. The concentrations of perfluoroalkyl carboxylic acids (PFCAs) in soil are negatively correlated with the length of carbon chain, log Kow, and log Koc. The carbon chain lengths of PFAAs are negatively correlated with the root-soil concentration factors (RCFs) and shoot-soil concentration factors (SCFs). The uptake of PFAAs by plant is influenced by physicochemical properties of PFAAs, plant physiology and soil environment. Further studies should be conducted to make up the inadequacy of existing knowledge on the behavior and fate of PFAAs in soil-plant system.

Aging of biodegradable-mulch-derived microplastics reduces their sorption capacity of atrazine.

Degradable plastics are gradually regarded as alternatives of conventional, synthetic organic polymers to reduce the plastics or microplastics (MPs) pollution; however, the reports upon environmental risk of degradable plastics are still limited. In order to evaluate the potential vector effect of biodegradable MPs on coexisting contaminants, sorption of atrazine onto pristine and ultraviolet-aged (UV) polybutylene adipate co-terephthalate (PBAT) MPs and polybutylene succinate co-terephthalate (PBST) MPs were investigated. The results showed that, UV aging led to more wrinkles and cracks on the surface, increased homogeneous chains proportion, enhanced hydrophobicity, and enlarged crystallinity of both MPs. The sorption kinetics of atrazine to MPs fitted well into pseudo-first-order (R2 = 0.809-0.996) and pseudo-second-order (R2 = 0.889-0.994) models. In the concentration range of 0.5-25 mg L-1, the sorption isotherm fitted into linear (R2 = 0.967-0.996) and Freundlich model (R2 = 0.972-0.997), indicating that the absorption partitioning was the dominant sorption mechanism. The partition coefficient (Kd) of atrazine to PBAT- MPs (40.11-66.01 L kg-1) was higher than that of PBST- MPs (34.34-57.96 L kg-1), and the Kd values of both MPs declined for aged MPs. The specific surface area, hydrophobicity, polarity and crystallinity of MPs jointly interpreted the changing sorption capacity of the MPs. In the present study, both aged PBAT- and aged PBST- MPs exhibited lower vector potential to atrazine than pristine MPs, suggesting reduced risk of being a pollutant carrier, which is of great significance for the development of biodegradable plastics.

Intercalation of salicylaldoxime into layered double hydroxide: Ultrafast and highly selective uptake of uranium from different water systems via versatile binding modes.

We report the first example of MgAl layered double hydroxide intercalated with salicylaldoxime (SA-LDH) which exhibits excellent uranium (U(VI)) capture performance. In U(VI) aqueous solutions, the SA-LDH shows a tremendous maximum U(VI) sorption capacity (qmU) of 502 mg·g-1, surpassing most known sorbents. For the aqueous solution with an initial U(VI) concentration (C0U) of âˆ¼ 10 ppm, ≥99.99 % uptake is achieved in a wide pH range of 3-10. At C0U âˆ¼ 20 ppm, >99 % uptake is reached within only 5 min, and pseudo-second-order kinetics rate constant (k2) of 44.9 g·mg-1·min-1 reaches the record value, placing the SA-LDH amongst the fastest U adsorbing materials reported to date. In contaminated seawater with 35 ppm of U while highly concentrated metal ions of Na+, Mg2+, Ca2+, and K+, the SA-LDH still displays exceptionally high selectivity and ultrafast extraction for UO22+, giving >95 % uptake of U(VI) within 5 min, and the k2 value of 0.308 g·mg-1·min-1 for seawater surpasses most reported values for aqueous solutions. Versatile binding modes toward U by SA-LDH, including complexation (UO22+ with SA- and/or CO32-), ion exchange and precipitation, contribute to the preferable uptake of U at different concentrations. X-ray absorption fine structure (XAFS) analyses demonstrate that one uranyl ion (UO22+) binds to two SA- anions and two H2O molecules forming 8-coordinated configuration. The U coordinates with O atom of the phenolic hydroxyl group and N atom of the -CN-O- group of SA-, forming a stable six-membered ring motif, which endows the fast and robust capture of U. The wonderful uranium trapping ability makes the SA-LDH among the best adsorbent used for uranium extraction from various solution systems including seawater.

Highly efficient removal of aqueous Hg(II) by FeS micro-flakes.

FeS (mackinawite) is known to be effective in the sorption of aqueous Hg(II). However, FeS nanoparticles are apt to aggregate and easy to be oxidized, which limits their wide applications. Here, we have synthesized FeS micro-flakes which can be uniformly dispersed in water without aggregation. Owing to the good stability and dispersibility, FeS micro-flakes exhibit high efficiency in the removal of Hg(II) from water. The sorption of Hg(II) on the FeS micro-flakes is more consistent with the pseudo-second-order kinetic model and Langmuir model, indicating that the sorption of Hg(II) is mainly monolayer sorption dominated by chemical sorption. The maximum sorption capacity is 2680 mg/g at pH 5.6 and 30 °C, significantly higher than those of FeS nanoparticles and other Hg(II) scavengers. The pH studies indicate that FeS (0.31 g/L) can effectively remove >97.6 % of 200 mg/L Hg(II) in the pH range of 2-12 at 30 °C. Powder X-ray diffraction, elemental and sorption analyses suggest that Hg(II) is removed via chemical precipitation and surface adsorption. This study demonstrates the potential and viability of FeS micro-flakes for efficient removal of aqueous Hg(II).

Efficient Remediation of Cadmium- and Lead-Contaminated Water by Using Fe-Modified Date Palm Waste Biochar-Based Adsorbents.

Heavy metals pollution of water resources is an emerging concern worldwide and seeks immediate attention. Date palm waste was transformed into biochar (BC), which was further modified through Fe-intercalation for the production of magnetic biochar (Fe-BC) in this study. The produced BC and Fe-BC were analyzed for chemical, proximate, surface, and elemental composition. The efficiency of the produced adsorbents to decontaminate the water from Cd2+ and Pb2+ ions was investigated through kinetics and an isotherm adsorption batch trial. Kinetics adsorption data fit well with the pseudo-second order and power function model, while equilibrium data were described well with the Langmuir and Freundlich isotherms. The maximum adsorption capacity as shown by the Langmuir model was the highest for Fe-BC for both Cd2+ (48.44 mg g-1) and Pb2+ (475.14 mg g-1), compared with that of BC (26.78 mg g-1 Cd2+ and 160.07 mg g-1 Pb2+). Both materials showed higher removal of Pb (36.34% and 99.90% on BC and Fe-BC, respectively) as compared with Cd (5.23% and 12.28% on BC and Fe-BC, respectively) from a binary solution. Overall, Fe-BC was more efficient in adsorbing both of the studied metals from contaminated water. The application of Fe-BC resulted in 89% higher adsorption of Cd2+ and 197% higher adsorption of Pb2+ from aqueous media as compared to BC. Kinetics and isotherm models as well as SEM-EDS analysis of the post-adsorption adsorbents suggested multiple adsorption mechanisms including chemisorption, pore-diffusion, and electrostatic interactions.

The role of biomass elemental composition and ion-exchange in metal sorption by algae.

The use of macroalgae, microalgae and cyanobacteria for metal sorption has been widely reported. Still, there are no studies allowing a direct comparison of the performance of these biomasses, especially while evaluating metal competition. The simultaneous sorption of Co2+, Cu2+, Ni2+ and Zn2+ present in a multi-elemental solution by six macroalgae, two microalgae and three cyanobacteria was evaluated. Brown macroalgae were shown to be the most promising biosorbent, with Undaria pinnatifida having a total metal sorption capacity of 0.6 mmol g-1. Overall, macroalgae performed better than microalgae, followed by cyanobacteria. Carboxyl groups were identified as being the main functional groups involved in metal sorption, and all biomass samples were found to be selective to Cu2+. This was linked not only to its higher complexation constant value with relevant functional groups when compared to the remaining metals, but also the Irving-Williams series. The release of K+ and Ca2+ to the aqueous solution during the metal sorption was followed. The obtained results suggest they are readily exchanged with metals in the solution, indicating the occurrence of an ion-exchange mechanism in metal sorption by most biomass. Red macroalgae are an exception to the reported trends, suggesting that their metal sorption mechanism may differ from the other biomass types.