Adsorbent For Phosphate Removal Research Articles

Adsorptive removal of phosphate from water with biochar from acacia tree modified with iron and magnesium oxides

A novel biochar (BC) from Acaciatortilis trees pruning waste was synthesized and tested for the removal of phosphate from aqueous solutions. The BC was prepared by calcination at 600 °C and doped with Fe3O4 and MgO by hydrothermal process. The presence of iron and magnesium ions in the modified BC was confirmed by EDS analysis and X-ray diffraction (XRD) methods. Both unmodified and doped BCs were tested for phosphate removal from synthetic 1–500 ppm aqueous solutions. While the unmodified BC did not show any significant removal of phosphate from aqueous solutions, the modified BC almost completely removed phosphate from water. The enhancement in removal efficiency is due to an increase in the overall surface charge and surface area of BC as a result of doping with Fe3O4 and MgO salts. The average porosity and BET surface area corresponding to the plain BC increased by more than 20% from 322 to 394 m2/g after modification by impregnation with iron oxide and magnesium oxide. The modificaiton of BC with Fe3O4 and MgO nanoparticles was observed to increase the point of zero electric charge (PZC) from pH 3.4 (corresponding to plain BC) to pH 5.3 (corresponding to modified BC). The adsorption process was very fast and a phosphate removal value of 82.5% was reached only after 30 min of adsorption, while the removal efficiency after 4 h of adsorption was 97.5%. The rapid removal efficiency in short contact time is attributed to the high surface area of BC and strong bonding between the modified BC surface and PO43− ions. The highest adsorption capacity was observed to correspond to 98.5 mg/g which was achieved at PO43− concentration of 500 ppm and pH 8.5. Moreover, after fitting the adsorption data onto four of the most widely used adsorption isotherm models, the adsorption of PO43− onto BC can be better described by the Langmuir isotherm model.

Sodium Alginate/UiO-66-NH2 Nanocomposite for Phosphate Removal.

Environmental pollution of phosphorus is becoming increasingly concerning, and phosphate removal from water has become an important issue for controlling eutrophication. Modified metal-organic framework (MOF) materials, such as UiO-66-NH2, are promising adsorbents for phosphate removal in aquatic environments due to their high specific surface area, high porosity, and open active metal sites. In this study, a millimeter-sized alginate/UiO-66-NH2 composite hydrogel modified by polyethyleneimine (UiO-66-NH2/SA@PEI) was prepared. The entrapping of UiO-66-NH2 in the alginate microspheres and its modification with PEI facilitate easy separation in addition to enhanced adsorption properties. The materials were characterized by SEM, FTIR, XRD, and BET. Static, dynamic, and cyclic adsorption experiments were conducted under different pH, temperature, adsorbent dosage, and initial concentration conditions to assess the phosphate adsorption ability of UiO-66-NH2/SA@PEI. Under optimal conditions of 65 °C and pH = 2, 0.05 g UiO-66-NH2/SA@PEI adsorbed 68.75 mg/g, and the adsorption rate remained at 99% after five cycles of UiO-66-NH2/SA@PEI. These results suggest that UiO-66-NH2/SA@PEI composite materials can be used as an effective adsorbent for phosphate removal from wastewater.

Lanthanum-loaded geopolymer for phosphate removal from agricultural runoff

The removal of phosphate from agricultural runoff is of great importance to mitigate an overabundance of nutrients discharging into receiving water bodies, which are susceptible to eutrophication. In this study, a La-loaded geopolymer was produced by adding metakaolin within an alkaline medium, consisting of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). The ratio of Na2SiO3:NaOH within the geopolymer slurry was manipulated to evaluate its effect on phosphate adsorption capacity. The 1.54 ratio yielded the highest adsorption capacity of 33.65 mg g−1. However, due to structural strength, safety, and economic considerations, the 2.0 ratio was used for the isotherm and kinetic adsorption testing. The La-loaded geopolymer exhibited higher phosphate removal in batch adsorption experiments at an acidic level (pH 4) and elevated temperature (40 °C). Moreover, ionic strength (3.5–20 mM) had a negligible impact on phosphate removal, indicating inner-sphere complexation as the main mechanism of adsorption. Additionally, bicarbonate and humic acid increased phosphate removal, whereas sulfate slightly decreased adsorption capacity. The La-loaded geopolymer was further evaluated using a synthetic agricultural solution, which yielded a Type III adsorption isotherm, demonstrating unrestricted multilayer phosphate adsorption. Results from this study verified the La-loaded geopolymer is a promising adsorbent for phosphate removal from agricultural runoff and underlined the importance of matrix effects on treatment performance.

Adsorption performance and mechanism of a starch-stabilized ferromanganese binary oxide for the removal of phosphate

Effective removal of phosphate from water is essential for preventing the eutrophication and worsening of water quality. This study aims to enhance phosphate removal by synthesizing starch-stabilized ferromanganese binary oxide (FMBO-S), discover the factors, and investigate adsorption mechanisms. FMBO and FMBO-S properties were studied using Scanning Electron Microscopy, BET analysis, Polydispersity Index (PDI), Fourier Transform Infrared Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). After starch loading, the average pore diameter increased from 14.89 Å to 25.16 Å, and significantly increased the pore volume in the mesopore region. FMBO-S showed a PDI value below 0.5 indicating homogeneous size dispersity and demonstrated faster and higher adsorption capacity: 61.24 mg g−1 > 28.57 mg g−1. Both FMBO and FMBO-S adsorption data fit well with the pseudo-second-order and Freundlich models, indicating a chemisorption and multilayered adsorption process. The phosphate adsorption by FMBO was pH-dependent, suggesting electrostatic attraction as the dominant mechanism. For the FMBO-S, phosphate adsorption was favored in a wide pH range, despite the weaker electrostatic attraction as evident from the point of zero charge and zeta potential values, indicating ligand exchange as a main mechanism. Moreover, the XPS analysis shows a significant change in the proportion of Fe species for FMBO-S than FMBO after phosphate adsorption, indicating significant involvement of Fe. Meanwhile, phosphate adsorption was almost unaffected by the presence of Cl−, NO3−, and SO42− anions, whereas CO32− significantly reduced the adsorption capacity. This study revealed that FMBO-S could be a promising, low-cost adsorbent for phosphate removal and recovery from water.

Adsorptive removal of phosphate from aqueous solutions using FeCl3‐immobilized melamine‐formaldehyde‐urea resin

AbstractThe surplus phosphorus in aquatic environments trigger eutrophication, an irreversible pollution stage marked by the rapid growth of algae and water plants, a decline in dissolved oxygen levels, and the emergence of dead zones. To address this critical issue, this study focuses on the removal of phosphorus in form of phosphate from aqueous solutions. The research involves the synthesis and characterization of FeCl3‐immobilized melamine‐formaldehyde‐urea resin, an innovative adsorbent, its characterization through Fourier transform infrared spectroscopy, and the evaluation of its adsorption capacity based on Langmuir and Freundlich equilibrium models. The experimental adsorption data fits well with pseudo‐second order kinetic model. Optimal adsorption parameters are carried with batch adsorption technique for 60 min using 0.5 g of adsorbent at pH = 2, achieving 15.55 mg g−1 adsorption capacity, and conducting experiments with tap‐water samples to replicate real‐world scenarios. The research findings have the potential to advance sustainable wastewater treatment technologies and contribute to the mitigation of nutrient pollution in aquatic ecosystems, addressing a pressing environmental concern.

Enhanced adsorption of phosphate by rice straw-based biochar prepared via metal impregnation and bio-template technology.

Phosphate removal from water through green, highly efficient technologies has received much attention. Biochar is an effective adsorbent for phosphate removal. However, adsorption capacity of phosphate on pristine rice straw-based biochar was not optimistic due to low anion exchange capacity. In this study, Fe-modified, Mg-modified and MgFe-modified rice straw-based biochar (Fe-BC, Mg-BC and MgFe-BC) were prepared by combining metal impregnation and biological template methods to improve the adsorption capacity of phosphate. The surface characteristics of biochar and the adsorption behavior of phosphate on biochar were investigated. The modified biochar had the specific surface area of 17.910-39.336 m2/g, and their surfaces were rich in a large number of functional groups and metal oxides. Phosphate release was observed on pristine rice straw-based biochar without metal impregnation. The maximum adsorption capacities of phosphate on MgFe-BC, Mg-BC and Fe-BC at 298K were 6.93, 5.75 and 0.23mg/g, respectively. Adsorption was a spontaneous endothermic process, while chemical adsorption dominated and electrostatic attraction and pores filling existed simultaneously. Based on the site energy distribution theory study, the standard deviation of MgFe-BC decreased from 6.96 to 4.64kJ/mol with temperature increasing, which proved that the higher the temperature would cause the lower heterogeneity. Moreover, the effects of pH, humic acid, co-existing ions and ionic strength on phosphate adsorption of MgFe-BC were also discussed. MgFe-BC with fine pores and efficient adsorption sites is an ideal adsorbent for phosphate removal from water.

Effect of Various Sizes of Calcined Marsh Clam Shell on Phosphate Removal from Aqueous Solution

Phosphorus is one of essential elements for sustaining life largely through phosphate, a compound containing the phosphate ion, PO43−. However, excessive phosphorus concentrations will cause eutrophication and this condition is considered as an environmental issue. The phosphorus sources are commonly from human activities; for instance, detergents, fertilisers, and industries. Although various adsorption techniques have been applied to remove phosphorus in water, the effect of different particle sizes of calcined marsh clam shells on phosphate removal has not been fully investigated, along with its adsorption kinetics and isotherms. This study investigates phosphate removal from synthetic solution onto calcined marsh clam shells (CMCs) with 5 different particle sizes: 0.075–0.15, 0.15–0.30, 0.30–0.60, 0.60–1.18, and 1.18–2.36 mm. The batch experiment used 2 g of adsorbent and synthetic potassium dihydrogen phosphate (KH2PO4) solution. The adsorbent size of 0.075 to 0.15 mm showed the highest removal (100%) efficiency due to high adsorption rate. The experimental data were further analysed using kinetics and isotherm models; the data fitted well with pseudo-second-order kinetic model (R2 = 0.9986) and Freundlich isotherm model (R2 = 0.8404). The potential of marsh clam shells as an adsorbent for phosphate removal in water is significant for future applications in wastewater treatment technology.

Preparation of an activated adsorbent from water treatment plant sludge for phosphate removal from wastewater: optimization, characterization, isotherm, and kinetics studies

Abstract Purifying water for diverse uses is vital, but concerns lie with the sustainability and accessibility of purification materials. As such, this study converted readily available water treatment plant sludge (WTPS) into activated adsorbent for phosphate removal in wastewater. WTPS was activated via thermal activation at 300 °C temperature and chemical activation processes of 3 M acid concentration, 4 h activation time, and 75 °C activation temperature, and then characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared, elemental analyzer, and differential scanning calorimetry. SEM and BET analyses revealed a highly porous adsorbent (279.2 m2/g) for efficient adsorption. On top of the activation process, preliminary experiments and numerical optimization using response surface methodology (RSM) were designed and conducted. Through optimizing conditions, it was found that 70 min of contact time, pH 3, 3 g/L adsorbent dose, and 30 mg/L initial phosphate concentration as optimal, yielding 83% removal efficiency. Furthermore, adsorption kinetics and isotherm models were examined and the second-order kinetics and Langmuir isotherm models indicated best fit. Notably, the activated sludge could be regenerated for three cycles before efficiency dropped below 70%. Thus, activated WTPS presents a promising, sustainable, and readily available adsorbent for phosphate removal in wastewater treatment.

Adsorptive Removal of Phosphate from Agricultural Effluent using Thermally and Non-Thermally Activated Sepiolite Clay

This study assessed the use of thermally activated sepiolite clay (TASC) and non-activated sepiolite clay (NASC) as adsorbents for phosphate adsorption from agricultural effluent. The effect of pH, temperature, dosage, and time on the adsorbates was investigated at pH 4-11, temperature 298 - 318k, contact time 30 – 120 minutes, and adsorbent dosage 0.2 - 4 g in 100 mL of agricultural effluent. Fourier-transformed infrared spectroscopy (FTIR) and Scanning electron microscope (SEM) techniques were used to determine adsorbent features. TASC and NASC exhibit an excellent capacity for adsorbing phosphate molecules. At equilibrium, the removal efficiency of phosphate at 4 different varying conditions of temperature, pH, adsorbent dosage, and time gave more than 100 % for TASC, while NASC also recorded over 100% adsorption of phosphate at 3 different varying conditions. The amount of phosphate adsorbed was found to decrease with an increase in temperature and contact time. The isotherm adsorption data fitted the Langmuir better than the Freundlich model, where the correlation coefficients of Langmuir and Freundlich were 0.9994 and 0.8901, respectively. The adsorption kinetics was better explained by the pseudo-first-order kinetic model with R2 values TASC (0.9999) and NASC (0.9999) than the second order with R2 value TASC (0.9984) and NASC (0.9820).

Ultrahigh-porosity Ranunculus-like MgO adsorbent coupled with predictive deep belief networks: A transformative method for phosphorus treatment

Phosphorus is a nonrenewable material with a finite supply on Earth; however, due to the rapid growth of the manufacturing industry, phosphorus contamination has become a global concern. Therefore, this study highlights the remarkable potential of ranunculus-like MgO (MO4–MO6) as superior adsorbents for phosphate removal and recovery. Furthermore, MO6 stands out with an impressive adsorption capacity of 596.88 mg/g and a high efficacy across a wide pH range (2–10) under varying coexisting ion concentrations. MO6 outperforms the top current adsorbents for phosphate removal. The process follows Pseudo-second-order and Langmuir models, indicating chemical interactions between the phosphate species and homogeneous MO6 monolayer. MO6 maintains 80 % removal and 96 % recovery after five cycles and adheres to the WHO and EUWFD regulations for residual elements in water. FT-IR and XPS analyses further reveal the underlying mechanisms, including ion exchange, electrostatic, and acid-base interactions. Ten machine learning (ML) models were applied to simultaneously predict multi-criteria (sorption capacity, removal efficiency, final pH, and Mg leakage) affected by 15 diverse environmental conditions. Traditional ML models and deep neural networks have poor accuracy, particularly for removal efficiency. However, a breakthrough was achieved by the developed deep belief network (DBN) with unparalleled performance (MAE = 1.3289, RMSE = 5.2552, R2 = 0.9926) across all output features, surpassing all current studies using thousands of data points for only one output factor. These captivating MO6 and DBN models also have immense potential for effectively applying in the real water test with error < 5 %, opening immense horizons for transformative methods, particularly in phosphate removal and recovery.

Designing a dual-functional ultrathin ZIF-L@GO adsorbent for simultaneous removal of phosphate and tetracycline hydrochloride: Adsorption capacity and mechanism

Inorganic phosphate and organic antibiotics, usually co-existing in wastewater, were difficult to simultaneously remove by common mono-functional adsorbents. In this work, by in-situ coating zeolitic imidazolate frameworks (ZIF-L) on graphene oxide (GO), a dual-functional ultrathin ZIF-L@GO-25 adsorbent was successfully prepared for efficient and simultaneous removal of phosphate and representative tetracycline hydrochloride (TC) from wastewater. ZIF-L@GO-25 exhibited maximum adsorption capacity for phosphate and TC respectively reached 116.3 ± 2.1 mg g−1 and 338.6 ± 6.7 mg g−1, benefiting abundant Zn-defect sites and dimethylimidazole rings exposed on its surface. Moreover, thanks to the specific innersphere complexation of Zn-defect/phosphate and π-π interaction between dimethylimidazole rings/TC molecules, > 95% removal efficiencies were achieved when the concentration of five competitive matters (Cl−, NO3−, SO42−, CO32− and humic acid) were 10 times that of phosphate/TC. Even with the binary pollutants co-existing system, only ∼3% removal decreases occurred on both phosphate and TC. Thus, this work proposed a novel preparation method of developing ZIF-based composite adsorbents for the deep treatment of actual phosphate/antibiotics-polluted wastewater.

Polydopamine modified cerium-based MOFs/ chitosan aerogel beads for the efficient phosphate removal

The metal organic frameworks (MOFs) are considered as the effective adsorbents for phosphate removal, while their ultrafine powders limit their practical application. In this study, we fabricate two chitosan (CS) gel beads added with different cerium-based MOFs and coated with PDA for phosphate adsorption. The MOFs doped in beads are CM1 and CM2, in which the Ce(III)/Ce(IV) ratio is 0.36 and 1.46, indicating CM2 is Ce(III) dominated and more suitable for phosphate removal. However, during the process of preparing gel beads, the mixture of chitosan and CM1/CM2 are added drop-by-drop to NaOH solution, leading to the decrease of Ce(III) contents in both of the two beads on account of oxidization. On this basis, in order to improve the phosphate uptake performance and enhance the mechanical strength, polydopamine (PDA) is applied to be coated on the outside. The adsorption capacities of CS-CM1 and CS-CM2 are no more than 20 mg/g higher than that of pure CS, which is also quite equal with the phosphate uptake of CS@PDA (63 mg/g). Due to the reduction of PDA, the content of Ce(III) increasing evidently in the two adsorbents. The maximum phosphate adsorption capacities are 146.8 mg/g and 114.8 mg/g for CS-CM1@PDA and CS-CM2@PDA, respectively. CS-CM2@PDA exhibits the largest treatment volume of ∼1166 BV in the fix-bed column study, much higher than that of CS-CM1@PDA (976 BV). The main reason is that Ce(III) could form binding with phosphate through ligand exchange and precipitation. Those inner-sphere interactions are much stronger than the electrostatic attraction between Ce(IV) and phosphate. Thus, due to this strong affinity, CS-CM2@PDA possessing a higher content of Ce(III) can capture phosphate more easier at low concentration. In summary, owing to reduction of PDA, the Cerium-based MOFs are successfully introduced in CS to realize excellent phosphate removal and exhibit a great prospect in application.

Simple synthesis of mesoporous ferrite materials as magnetic adsorbents for phosphate removal

AbstractMesoporous MFe2O4 materials (M = Mn, Cu, and Co) as magnetic adsorbents for phosphate removal were synthesized by a simple coprecipitation method without annealing at high temperatures. Several techniques, including powder X‐ray diffraction, field emission electron scanning microscopy, nitrogen adsorption‐desorption and vibrating sample magnetometry were used to characterize the samples. The effects of M2+ ions on their point of zero charge and their phosphate adsorption capacity were investigated. All three samples consist of nanosized particles with cubic spinel structure and ferromagnetic properties, which allows them to be easily separated from aqueous effluents using a magnet. According to the batch experiments, the adsorption isotherms and the adsorption kinetics for these mesoporous materials are well fitted with the nonlinear Langmuir model and the nonlinear pseudo‐second‐order model, respectively. Among them, CuFe2O4 powder showed the best phosphate adsorption performance with the maximum P adsorption capacity of 27.49 mgP g‐1, which can be assigned to the highest surface area and the high pH value at its point of zero charge.

Adsorption Removal of Phosphate from Rural Domestic Sewage by Ca-Modified Biochar Derived from Waste Eggshell and Sawdust

In recent years, in order to improve the rural living environment, rural domestic sewage treatment has received more and more attention in China. However, the standard compliance rate of total phosphorus (TP) in rural domestic sewage after treatment is very low, and TP has become the main pollutant that prevents rural domestic sewage treatment facilities from meeting water pollutants discharge standards. In this study, to prepare calcium-modified biochar composites (E-BC) by one-step pyrolysis, waste eggshell (E) was employed as a calcium source and waste pine sawdust (BC) was employed as a carbon source. The E-BC composites produced were effective in adsorbing phosphate (P) from aqueous solutions in a broad pH range of 3–11, with good adsorption selectivity. E-BC’s adsorption capacity for P increased as the pyrolysis temperature increased from 700 °C to 900 °C, which was attributed to the higher specific surface area and calcium oxide content at higher pyrolysis temperatures. The E-BC sample, which was made from eggshell (filtered through 100 mesh sieves) and pine sawdust (filtered through 100 mesh sieves) with a mass ratio of 2:1 and a pyrolysis temperature of 900 °C, had a maximum adsorption capacity of 301 mg/g. The Langmuir model and pseudo second-order model were the best at describing the adsorption process, and the predominant sorption mechanism for P is the chemisorption reaction of calcium oxide or calcium hydroxide with phosphate to create hydroxyapatite. E-BC can effectively remove P from rural domestic sewage. The total phosphorus (TP) removal rate in rural domestic sewage ranges from 95.3 to 99.5%. After adsorption treatment, the discharge of TP in rural sewage meets the second-grade (TP &lt; 3 mg/L) or even the first-grade (TP &lt; 2 mg/L). This study provides an experimental basis for efficient P removal using E-BC adsorbent materials and suggests possible applications in rural domestic sewage.

Efficient Adsorption Removal of Phosphate from Rural Domestic Sewage by Waste Eggshell-Modified Peanut Shell Biochar Adsorbent Materials.

In order to promote the improvement of the rural living environment, the treatment of rural domestic sewage has attracted much attention in China. Meanwhile, the rural regions' sewage discharge standards are becoming increasingly stringent. However, the standard compliance rate of total phosphorus (TP) is very low, and TP has become the main limiting pollutant for the water pollutants discharge standards of rural domestic sewage treatment facilities. In this study, waste eggshell (E) was employed as a calcium source, and waste peanut shell (C) was employed as a carbon source to prepare calcium-modified biochar adsorbent materials (E-C). The resulting E-C adsorbent materials demonstrated efficient phosphate (P) adsorption from aqueous solutions over the initial pH range of 6-9 and had adsorption selectivity. At an eggshell and peanut shell mass ratio of 1:1 and a pyrolysis temperature of 800 °C, the experimental maximum adsorption capacity was 191.1 mg/g. The pseudo second-order model and Langmuir model were best at describing the adsorption process. The dominant sorption mechanism for P is that Ca(OH)2 is loaded on biochar with P to form Ca5(PO4)3OH precipitate. E-C was found to be very effective for the treatment of rural domestic sewage. The removal rate of TP in rural domestic sewage was 91-95.9%. After adsorption treatment, the discharge of TP in rural sewage met the second-grade (TP < 3 mg/L) and even first-grade (TP < 2 mg/L). This study provides an experimental basis for efficient P removal by E-C adsorbent materials and suggests possible applications in rural domestic sewage.

The adsorption behavior and mechanism for arsenate by lanthanum-loaded biochar with different modification methods

Lanthanum (La)-loaded biochar (BC) was considered as an efficient adsorbent for phosphate removal in wastewater. Arsenate has a similar chemical structure to phosphate, however, performance and mechanisms of arsenate adsorption onto La-doped biochar are less studied and remain unclear. In this study, La-modified biochar (BC) was prepared using two dinstinct methods: pyrolysis of LaNO3-doped rice husk (pre-pyrolysis modification, referred to as La-BC) and pyrolysis of LaNO3-doped rice husk biochar (post-pyrolysis modification, referred to as BC-La). Isotherm experiments showed that the maximum arsenate adsorption content onto La-BC and BC-La was similar, respectively of 21.3 mg g−1 and 16.5 mg g−1 at pH = 5. Combined results of SEM-EDS, FTIR, and XPS analyzing revealed that La oxides and hydroxides loaded on BC played a vital role in arsenate adsorption. Electrostatic attraction and ligand exchange were considered as key mechanisms for arsenate adsorption. Compared to La-BC, the results revealed that La oxides/hydroxides exhibited more crystalline structures on BC-La. Moreover, the BC-La displayed more efficient adsorption capabilities over a wider pH range (pH 4–10) than La-BC. The XPS O1s spectra analysis confirmed the formation of different inner-sphere complexes on La-BC and BC-La. Results of this study revealed mechanisms of arsenate adsorption onto La-modified biochar, and highlighted that the adsorption behavior of arsenate onto La-modified biochar could be significantly influenced by modification methods.

Cerium(IV) chitosan-based hydrogel composite for efficient adsorptive removal of phosphates(V) from aqueous solutions

The excess presence of phosphate(V) ions in the biosphere is one of the most serious problems that negatively affect aqueous biocenosis. Thus, phosphates(V) separation is considered to be important for sustainable development. In the presented study, an original cerium(IV)-modified chitosan-based hydrogel (Ce-CTS) was developed using the chemical co-precipitation method and then used as an adsorbent for efficient removal of phosphate(V) ions from their aqueous solutions. From the scientific point of view, it represents a completely new physicochemical system. It was found that the adsorptive removal of phosphate(V) anions by the Ce-CTS adsorbent exceeded 98% efficiency which is ca. 4-times higher compared with the chitosan-based hydrogel without any modification (non-cross-linked CTS). The best result of the adsorption capacity of phosphates(V) on the Ce-CTS adsorbent, equal to 71.6 mg/g, was a result of adsorption from a solution with an initial phosphate(V) concentration 9.76 mg/dm3 and pH 7, an adsorbent dose of 1 g/dm3, temperature 20 °C. The equilibrium interphase distribution data for the Ce-CTS adsorbent and aqueous solution of phosphates(V) agreed with the theoretical Redlich-Peterson and Hill adsorption isotherm models. From the kinetic point of view, the pseudo-second-order model explained the phosphates(V) adsorption rate for Ce-CTS adsorbent the best. The specific effect of porous structure of adsorbent influencing the diffusional mass transfer resistances was identified using Weber-Morris kinetic model. The thermodynamic study showed that the process was exothermic and the adsorption ran spontaneously. Modification of CTS with cerium(IV) resulted in the significant enhancement of the chitosan properties towards both physical adsorption (an increase of the point of zero charge of adsorbent), and chemical adsorption (through the presence of Ce(IV) that demonstrates a chemical affinity for phosphate(V) anions). The elaborated and experimentally verified highly effective adsorbent can be successfully applied to uptake phosphates(V) from aqueous systems. The Ce-CTS adsorbent is stable in the conditions of the adsorption process, no changes in the adsorbent structure or leaching of the inorganic filling were observed.

Synthesis of porous Mg(OH)2 nanowires for phosphate removal from water

Mg(OH)2 is an inorganic material with a wide range of applications in water purification, especially the adsorption of phosphates. In this study, porous Mg(OH)2 nanowires were synthesized by a facile hydrothermal conversion method to remove phosphate from aqueous solutions. The porous Mg(OH)2 nanowires can be readily obtained using magnesium hydroxide chloride hydrate (MHCH) whiskers as precursors in NaOH ethanol-water solution and exhibit good adsorption performance for phosphate. OH- ions diffused into the lattice to bind with Mg2+, while H2O and Cl- escaped from the lattice, resulting in the formation of porous Mg(OH)2 nanowires. The ethanol prevented the collapse of these pores. The adsorption process of phosphate on the porous Mg(OH)2 nanowires conforms to pseudo-second-order kinetics and is spontaneous, endothermic, and entropy-increasing. It was substantiated to be a complexation process of Mg2+ and HPO42- and H2PO4-. The maximum adsorption amount at 313 K was 162.15 mg g−1, minimally affected by coexisting ions and demonstrated good recycling performance. This work highlights the potential of porous Mg(OH)2 nanowires as an eco-friendly and low-cost adsorbent for phosphate removal and recovery.

Synthesis of LDH/Alginate composite beads as a potential adsorbent for phosphate removal: kinetic and equilibrium studies

Synthesis of LDH/Alginate composite beads as a potential adsorbent for phosphate removal: kinetic and equilibrium studies

Porous La2O2CO3 derived from solvent-guided metal-organic frameworks for high-efficient phosphorus removal

La-based materials have garnered considerable attention as potential adsorbents for phosphate removal because they capture phosphate with high affinity, producing an ultralow phosphorous-concentration output. Herein, La-based metal–organic frameworks (La–MOFs, La-1,3,5-benzentricarboxylate) with tunable structures were fabricated by regulating the coordination solvent environment, which largely determines both the pore structure and chemical components of their corresponding La2O2CO3 derivatives and the phosphate adsorption performance. A porous La2O2CO3 derivative (W–D T500) derived from the water/N,N-dimethylformamide (DMF) guided La–MOF showed abundant mesopores and a high surface area, because the pore-opening degree under high-temperature pyrolysis is higher in W–D T500 than in the La2O2CO3 derivative obtained from the water/ethanol solvent–guided La–MOF. W–D T500 also had higher La (78.3%) and carbonate contents of the crystal structure owing to the higher efficiency of carbon conversion to carbonate-oxides in W–D T500. Consequently, the porous La2O2CO3 derivative W–D T500 exhibited superior phosphate adsorption capacity (91.6 mg P/g), high adsorption selectivity, and excellent recycling performance. Phosphate was attached to the La2O2CO3 adsorbents via a ligand-exchange mechanism between phosphate and CO32−/–OH. This study provides a solvent guidance strategy to construct functional La–MOFs and La2O2CO3 derivatives for excellent phosphate removal.