Multiple bimetallic (Al-La or Fe-La) hydroxides embedded in cellulose/graphene hybrids for uptake of fluoride with phosphate surroundings

In Situ Synthesis of Rare-Earth Hybridized Functional Core-Shell Architectures from Microporous Salt Templates and Capacitance-Adsorption Correlation Mechanisms

Biochar Porous Carbon (BPC) has become a research hotspot in the fields of energy storage, conversion, catalysis, adsorption, and separation engineering. However, the key problem of pore structure liable to collapse has not yet been addressed effectively. Here, an innovative salt ionic coordination modulation technique is reported to synthesize a new core-shell structure of BPC (Dual-doped porous carbonaceous materials, RHPC3@LaYO3) by the asymmetric load of the f orbital ion, which prevents pore structural collapse. The result shows that the novel asymmetric supercapacitors (ASCs) with an excellent energy density (193.11 Wh·kg-1) and capacitance (267.14 F·g-1) by assembling the prepared porous BPC carrier and RHPC3@LaYO3, which surpass the typical supercapacitor. In order to elucidate the association between adsorption and capacitance, the adsorption coexistence equation (MACE) is constructed with the aim of providing a comprehensive explanation for the mechanism of single-multilayer adsorption. Furthermore, a specific linkage mechanism is discovered using adsorption/ desorption properties to validate the pros/cons of capacitive properties. These results demonstrate the potential of renewable biomass materials as ASCs, which can provide new ideas for the construction of an evaluation approach for the performance of future efficient multi-reaction energy storage devices.

Vertical porous aerogel based on polypyrrole and bimetallic modified β-cyclodextrin polymer-chitosan for efficient solar evaporation

Solar-driven interfacial evaporation (SDIE) stands out as a prospective technology for freshwater production, playing a significant role in mitigating global water scarcity. Herein, a cyclodextrin polymer/chitosan composite aerogel (PPy-La/Al@CDP-CS) with vertically aligned channels was prepared as a solar evaporator for efficient solar steam generation. The vertically aligned pore structure, achieved through directional freezing assisted by liquid nitrogen, not only improves water transport during evaporation but also enhances light absorption through multiple reflections of sunlight within the pores. The polypyrrole particles sprayed on the surface of the aerogel acted as a light-absorbing layer, resulting in an impressive absorbance of 98.15 % under wetting conditions. The aerogel has an evaporation rate of 1.85 kg m-2 h-1 under 1 kW m-2 irradiation. Notably, the vertical pore structure of the aerogel allows it to exhibit excellent evaporation performance and salt resistance even in highly concentrated salt solutions. Furthermore, this aerogel is an excellent solar-driven interfacial evaporator for purifying seawater and fluoride-containing wastewater. This photothermal aerogel has the advantages of excellent performance, low cost, and environmental friendliness, and thus this work provides a new approach to the design and fabrication of solar photothermal materials for water treatment.

Bimetallic capture sites on porous La/Bi hydroxyl double salts for efficient phosphate adsorption: Multiple active centers and excellent selective properties

The rapid development of modern agriculture aggravated water eutrophication. Therein, efficient and selective removal of phosphorus in water is the key to alleviating eutrophication. It is well known that lanthanum (La)-based material is a kind of outstanding phosphorus-locking agent. Therefore, improving the property of La-based adsorbents is a hot topic in this field. Herein, novel porous hydroxyl double salts (La/Bi-HDS) with bimetallic capture sites were prepared. The experimental result shows that La/Bi-HDS could maintain the high removal rate in the solution with a higher concentration of competing ions and the maximum P adsorption quantity of La/Bi-HDS attains 168.12 mg/g. Mechanistic studies supported by density functional theory (DFT) calculation demonstrate that introducing Bi3+ optimizes the electronic structure of La, reducing adsorption energy. In addition, the surface analysis shows that the introduction of Bi, which increases the pore size and volume of the material, improves the utilization efficiency of the active site. In a word, the introduction of Bi element as a strategy of killing two birds with one stone successfully improved the performance of La-based adsorbent. It provided a new direction for developing an efficient phosphorus-locking agent.

Fluoride remediation from on-site wastewater using optimized bauxite nanocomposite (Bx-Ce-La@500): Synthesis maximization, and mechanism of F─ removal

Bauxite is a widely available Al-O-rich mineral with great potential for abating fluoride. However, low adsorption capacity, a narrow workable pH range, and a lack of clarity on the best removal mechanism hinder its application. In this work, a highly efficient bauxite nanocomposite (Bx-Ce-La@500) was synthesized via doping and pyrolysis, and its fluoride adsorption in industrial wastewater was examined. Doping Ce/La synergistically improved the fluoride adsorption affinity of the composite (from pH_PZC 8.0 ~ 10.0) and enhanced the •OH. The materials were characterized by SEM-EDS, BET, XRD, and TGA while XPS, FTIR, and DFT were used to investigate the mechanism of fluoride sorption. Results show that Bx-Ce-La@ 500 has a positive zeta potential of 26.3-23.1 mV from pH 1~ 10. The Langmuir model was the best fit with a maximum adsorption capacity of 88.13 mg/g and removal efficiency up to 100% in 50 ppm F^- solution. The high F^- removal was attributed to the enhanced surface affinity and the formation of adequate •OH on the material. Except for carbonate and phosphate ions, other ions exhibited negligible effects and the selective removal of F^- in real wastewater was high. The main mechanism of adsorption was the ligand/ion exchange and electrostatic attraction.

Enhanced removal of phosphate using pomegranate peel-modified nickel‑lanthanum hydroxide

In this work, a bimetallic Ni/La nanoparticle-laded biosorbent was fabricated from pomegranate fibers by solvothermal synthesis method. The material exhibited a high-efficient phosphate removal capability. The results of the characterization analysis showed that the surface of pomegranate fibers was rough and evenly coated with Ni and La after modification, and the specific surface area of Ni-La@Peel increased to 50.20 m²/g, providing a large number of adsorption sites for phosphate removal. The maximum phosphate removal rate of adsorbent was higher than 97% in a wide pH range (3.7-10.8). The maximum adsorption capacities of Ni-La@Peel were 226.55 mg-P/g and 220.31 mg-P/g under alkaline and acidic conditions, respectively, as calculated using the Langmuir model. Meanwhile, all the results were consistent with the Langmuir isothermal (R² = 0.99) and kinetic pseudo-second order models (R² = 0.99), indicating that the phosphate removal mechanism of Ni-La@Peel was mainly related to homogeneous chemisorption. Experimental results showed that in the presence of other anions, such as chloride, sulfate, nitrate, bromide and fluoride, the adsorption capacity of phosphate was only reduced by about 10% compared to the blank sample individually. In addition, the phosphate removal efficiency of Ni-La@Peel remained 82.05% at 7th adsorption-desorption cycle. These findings show that Ni-La@Peel is a promising material for purification of phosphate-containing wastewater.

Enhanced fluoride removal from water by nanosized cerium oxides impregnated porous polystyrene anion exchanger

Efficient elimination of fluoride from wastewater is an urgent need for ensuring water safety. In the present study, a stable and reusable nanocomposite (NCO@PAE) was synthesized by impregnating nanosized cerium oxides (NCO) inside a porous polystyrene anion exchanger (PAE) host for efficient fluoride removal from wastewater. The newly fabricated NCO@PAE exhibited excellent resistance to acid and alkali environment, allowing it to be utilized in a wide pH range (2-12). Fluoride uptake onto NCO@PAE was a pH-dependent process, which could reach the maximum capacity at pH 3.0. Compared with its host PAE, NCO@PAE showed conspicuous adsorption affinity towards fluoride in the coexistence of other competing anions at high concentrations. Adsorption kinetics confirmed its high efficiency for achieving equilibrium within 120 min. Fixed-bed adsorption runs demonstrated that the effective processing capacity of NCO@PAE for synthetic fluoride-containing wastewater (initial fluoride 2.5 mg/L) was about ~330 BV (bed volume), while only 22 BV for the host PAE. The exhausted NCO@PAE could be effectively revived by a simple in-situ desorption method for long-term cycle operation without conspicuous capacity loss. All the results indicated that NCO@PAE is a reliable and promising adsorbent for water defluoridation.

Removal of F- and organic matter from coking wastewater by coupling dosing FeCl3 and AlCl3

Coagulation and precipitation is a widely applied method to remove F^- from wastewater. In this work, the effect of coagulation on the removal of F^- and organic matter from coking wastewater was studied using AlCl₃ and FeCl₃ as compound coagulants. The removal rates of F^- and organic matter under different coagulant doses and pH conditions were investigated. The results show that the highest removal rates of F^- by AlCl₃ and FeCl₃ are 94.4% and 25.4%, respectively; when the dosage is 10 mmol/L, the TOC removal rates of FeCl₃ and AlCl₃ reach 20.4% and 34.7%, respectively. Therefore, the removal rate of F^- by AlCl₃ is higher than that of FeCl₃, but the removal rate of organic matter by FeCl₃ is relatively higher. The addition of Ca²⁺ can promote the removal of F^-, but the removal rate of organic matter decreases. In addition, by investigating the effects of different pH and Fe-Al ratio on the removal rate, the removal effect of adding FeCl₃ and AlCl₃ at the same time was discussed. The results show that the most suitable working condition for the removal of organic matter and F^- is that the pH is 6.5 and the molar ratio of Al/Fe is 8:2. Overall, the removal mechanism of F^- and organic matter in coking wastewater by FeCl₃ and AlCl₃ was explored in this study. The experimental results can provide reference for the advanced treatment of coking wastewater.

The enhanced removal of phosphate by structural defects and competitive fluoride adsorption on cerium-based adsorbent

Trivalent cerium (Ce(Ⅲ)) was demonstrated to have great potential for phosphate (P) removal. Besides the valence states, the relationship of nano-structure and adsorption capacity needs further study to explore more efficient adsorbents. Herein, a series of Ce(Ⅲ)-terephthalate (BDC) metal-organic framework (MOF) with linker deficiencies are fabricated to achieve excellent P capture. The defective density can be increased by decreasing the reaction time and the ratio of organic linkers/metal. TGA reveals Ce-BDC-48 synthesized with BDC:Ce ratio of 1:1 for 48 h possessed 2.5 missing linkers per inorganic node. And the P uptake of Ce-BDC-48 was 35% higher than that of Ce-BDC-72 without defects. The maximum adsorption capacity of Ce-BDC-48 was 278.8 mg/g for P and 128.0 mg/g for fluoride (F), respectively. The adsorption mechanism illustrates that both P and F mainly focus on the Ce(Ⅲ) active sites to achieve ligand exchange. The competing adsorption of P and F at the lower concentration of F (50 mg/L) indicates that the interference of F for P removal is insignificant on account of the selective preferential order of P. However, with the increment of F concentration (100 mg/L), amount of F with small sizes gathering around the adsorbent surface enlarge the steric hindrance to hinder the access of P, leading to the sharp decline of P uptake. This study not only provides promising candidate by the design of structural defects for the P removal in practical application but also give a deep analysis on the adsorption mechanism of P with competing F surrounded.

Enhanced removal of tris(2-chloroethyl) phosphate using a resin-based nanocomposite hydrated iron oxide through a Fenton-like process: Capacity evaluation and pathways

The effective removal of organophosphorus compounds (OPs) effectively from water environment remains an important but challenging task. In this study, a resin-based nanocomposite of hydrated iron oxide (HD1) was used as Fenton-like catalyst for effectively catalyzing the decomposition of hydrogen peroxide to degrade tris(2-chloroethyl) phosphate (TCEP). The results showed that HD1 was successfully prepared, which had great versatility, catalytic performance and adsorption capacity. Besides, HD1/H₂O₂ was capable of degrading TCEP completely with less than 0.2 mg/L of inorganic phosphorus (IP) in the effluent at the initial TCEP of 38 mg/L, pH = 4, H₂O₂ dosage of 20 mM, and the K_obs could result in about 1.0530 min^-1 under identical conditions. More attractively, inorganic ions (i.e., Cl-, CO₃²-, SO₄²-, NO₃-, HCO₃-, Ca²⁺, and Mg²⁺) exhibited moderate effect on TCEP degradation. The negative effect of natural organic matters (NOM) (i.e., HA) on the degradation of TCEP was responsible for competition for the active oxygen species. Combined with electron paramagnetic resonance (EPR) spectra, X-ray photoelectron spectroscopy (XPS) and other analytical methods and radical quenching experiments, the possible removal process of TCEP was discussed, including two processes of oxidative degradation and immobilization of IP. Besides, hydroxyl radicals (•OH) was the key active species that contributed to TCEP degradation through hydroxylation-oxidation and C-O bond cracking, and specificity adsorption of HFO on IP was revealed. Furthermore, the results showed that HD1 had desirable acid and alkali resistance. In the continuous running fixed bed column experiment, HD1 showed a satisfactory performance in cycle operations. This work proposed a new enhanced process for removing TCEP in water environment by HD1/H₂O₂, and the multi-functional material, HD1 was promising in treatment of water containing organic phosphorus pollutants. This will be believed that this study will provide new ideas and new materials for the treatment of organic phosphorus-based organic pollutants, and lay the foundation for further deepening and expanding the application of adsorption resins in the field of water pollution control.

Adsorptive removal of phosphate by the bimetallic hydroxide nanocomposites embedded in pomegranate peel

This study aimed to fabricate new and effective material for the efficiency of phosphate adsorption. Two types of adsorbent materials, the zirconium hydroxides embedded in pomegranate peel (Zr/Peel) and zirconium-lanthanum hydroxides embedded in pomegranate peel (Zr-La/Peel) were developed. Scanning electronic microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) were evaluated to give insight into the physicochemical properties of these adsorbents. Zr-La/Peel exceeded the adsorption efficiency of Zr/Peel adsorbents in batch adsorption experiments at the same pH level. The peel as a host can strive to have a strong "shielding effect" to increase the steadiness of the entrenched Zr and La elements. La and Zr are hydroxide metals that emit many hydrogen ions during the hydrolysis reaction, which contribute to protonation and electrostatic attraction. The highest adsorption capacity of La-Zr/Peel for phosphate was calculated to be 40.21 mg/g, and pseudo second-order equation is very well fitted for kinetic adsorption. Phosphate adsorption efficiency was reduced by an increase of pH. With the background of coexisting Cl^-, little effect on adsorption efficiency was observed, while adsorption capacities were reduced by almost 20-30% with the coexistence of [Formula: see text] , [Formula: see text] and humic acid (HA).