Efficient Phosphate Adsorption Research Articles

Enhanced phosphorus removal from anoxic water using oxygen-carrying iron-rich biochar: Combined roles of adsorption and keystone taxa

Anthropogenic enrichment of phosphorus (P) in water environment can cause eutrophication, harmful algal blooms, and water quality deterioration. Adsorbents are often used for the removal and recovery of P from water, however, P is highly susceptible to re-release in anoxic benthic environments. As a response, this study prepared oxygen-carrying iron-rich biochar (O-Fe-BC) as an effective oxygen micro-nanobubble carrier (Q = 8.7024 cm³/g STP at 1.5 MPa) and P adsorbent (qm = 16.7097 mg P/g, q0.1 = 3.1974 mg P/g). Over the 90-day experimental period with O-Fe-BC, dissolved oxygen (DO) levels in the overlying water could maintain at ∼4 mg/L (peaking at ∼9.5 mg/L), and total phosphorus (TP) and soluble reactive phosphorus (SRP) levels decreased by over 96 %. The higher inorganic phosphorus content in the surface sediment-biochar mixture, along with the lower labile P and Fe concentration in the sediment pore water in the O-Fe-BC group compared to other groups, suggested the enhanced P immobilization. Further mechanism exploration revealed the combined roles of adsorption and microbial response, in which O-Fe-BC achieved efficient phosphate adsorption primarily through inner-sphere complexation via ligand exchange and keystone taxa (particularly Candidatus Electronema) played a crucial role in driving water chemistry divergence. Specially, these cable bacteria could provide large pools of Fe oxides in the surface sediment, binding with P to prevent its release, as supported by significant correlations between Ca. Electronema abundance and oxidation–reduction potential (ORP), TP, SRP, and sediment Fe-P variations. Additionally, a pot experiment with mung bean seedlings showed that the recovered O-Fe-BC significantly promoted the seed germination and growth, indicating its potential as a novel material for removing and recovering P from eutrophic waters. Taken together, our work provided a promising strategy for sustainable anoxia and P pollution mitigation, and also highlighted the indispensable roles of inner-sphere adsorption in P recovery and microbial keystone taxa in P cycling regulation.

Zirconium(IV)-Loaded Amino Functionalized Walnut Shell for Efficient Adsorption of Phosphate and 2,4-Dichlorophenoxyacetic Acid from Water

Zirconium(IV)-Loaded Amino Functionalized Walnut Shell for Efficient Adsorption of Phosphate and 2,4-Dichlorophenoxyacetic Acid from Water

Efficient Phosphate Adsorption from Groundwater by Mn-FeOOHs

Manganese co-precipitated with goethite (Mn-FeOOH) is ubiquitous within (sub-)surface environments, which are considered one of the most important sinks for phosphorus pollution management. Accordingly, various mole ratios of Mn-FeOOHs are synthesized and characterized by XRD, FE-SEM, FTIR, BET, XPS, hysteresis loop, acid–base titration and zero potential. According to XRD and FESEM images, the substitution of Mn causes subtle alterations in the microstructure and crystal structure of goethite, and the morphology of Mn-FeOOHs is transformed from needle-shaped goethite to a short-rod-shaped rough surface with increasing Mn substitution. Based on the analysis of BET and acid–base titration, the substitution of Mn into goethite significantly improved the surface area, pore volume, surface properties and active sites of goethite, thereby establishing a theoretical basis for effective subsequent adsorption. Batch experiment results show that the removal rate of phosphate decreases with the increasing solution pH, indicating that acidic groundwater conditions are more conducive to the removal of phosphate. In addition, the adsorption of phosphate on Mn-FeOOHs is independent of ionic strength, indicating that the inner-sphere surface complexation predominated their adsorption behaviors. The isotherm experiment results showed that Mn-G15 exhibits the strongest adsorption capacity for phosphate at pH 5.5 and T = 318 K, with a maximum adsorption capacity of 87.18 mg/g. These findings highlighted the effect of Mn content on the fixation of phosphate onto Mn-FeOOHs from (sub-)surface environments in pollution management.

New Zein Protein Composites with High Performance in Phosphate Removal, Intrinsic Antibacterial, and Drug Delivery Capabilities.

Herein, poly(N-(4-aminophenyl)methacrylamide)-carbon nano-onions [abbreviated as PAPMA-CNOs (f-CNOs)] integrated gallic acid cross-linked zein composite fibers (ZG/f-CNOs) were developed for the removal/recovery of phosphate from wastewater along with controlled drug delivery and intrinsic antibacterial characteristics. The composite fibers were produced by Forcespinning followed by a heat-pressure technique. The obtained ZG/f-CNOs composite fibers presented several favorable characteristics of nanoadsorbents and drug carriers. The composite fibers exhibited excellent adsorption capabilities for phosphate ions. The adsorption assessment demonstrated that composite fibers process highly selective sequestration of phosphate ions from polluted water, even in the presence of competing anions. The ZG/f-CNOs composite fibers presented a maximum phosphate adsorption capacity (qmax) of 2500 mg/g at pH 7.0. This represents the most efficient phosphate adsorption system among all of the reported nanocomposites to date. The isotherm studies and adsorption kinetics of the adsorbent showed that the adsorption experiments followed the pseudo-second-order and Langmuir isotherm model (R2 = 0.9999). After 13 adsorption/desorption cycles, the adsorbent could still maintain its adsorption efficiency of 96-98% at pH 7.0 while maintaining stability under thermal and chemical conditions. The results mark significant progress in the design of composite fibers for removing phosphates from wastewater, potentially aiding in alleviating eutrophication effects. Owing to the f-CNOs incorporation, ZG/f-CNOs composite fibers exhibited controlled drug delivery. An antibiotic azithromycin drug-encapsulated composite fibers presented a pH-mediated drug release in a controlled manner over 18 days. Furthermore, the composite fibers displayed excellent antibacterial efficiency against Gram-positive and Gram-negative bacteria without causing resistance. In addition, zein composite fibers showed augmented mechanical properties due to the presence of f-CNOs within the zein matrix. Nonetheless, the robust zein composite fibers with inherent stimuli-responsive drug delivery, antibacterial properties, and phosphate adsorption properties can be considered promising multifunctional composites for biomedical applications and environmental remediation.

Efficient phosphate adsorption in aqueous solution using nano-zirconia impregnated spent coffee grounds and preliminary application as a slow-release fertilizer

ABSTRACT In this study, the development of a nano-biocomposite adsorbent based on spent coffee grounds (SCG) and nano-Zirconia (n-ZrO2) was presented to meet the increasing demand for effective and low-cost phosphate adsorbents and contribute to sustainable development goals (SDGs). The adsorption performance of raw SCG and SCG modified with n-ZrO2 (n-ZrO2-mSCG) was tested. The characterization of materials was performed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Dispersive X-ray spectroscopy (EDS), and Transmission electron microscopy (TEM). The n-ZrO2-mSCG exhibited superior adsorption capacity compared to SCG. The influences on the adsorption of factors such as initial concentration, pH, stirring time, temperature, and coexisting ions were evaluated. The results showed the maximal adsorption capacity of modified SCG was 15.8 mg/g at pH 2, using a stirring time of 150 mins. Among investigated coexisting anions, sulfate (SO4 2-) and bicarbonate (HCO3 −) affected the phosphate adsorption performance of n-ZrO2-mSCG, when they existed in aqueous solution at predominant levels. The n-ZrO2-mSCG displayed high selectivity toward phosphate and sustained efficacious phosphate adsorption after three successive cycles of adsorption/desorption, proposing a prospective low-cost and reusable adsorbent material for phosphate removal and a potential alternative to conventional fertilizers.

Efficiency and mechanism of phosphate adsorption and desorption of a novel Mg-loaded biochar material.

Phosphate removal is complicated by the need for resource recovery. Biochar shows promise for efficient phosphate adsorption, but it must be modified to enhance its adsorption capacity. In this work, magnesium (Mg)-loaded biochar was synthesized through a two-step dipping and calcination process, and the MgBC600 product was used to adsorb phosphate from simulated water and biogas slurry wastewater. The phosphate adsorption capacity of Mg-loaded biochar was 109.35mg/g, which was 12 times higher than that of unmodified biochar. The R2 of the Langmuir and pseudo-second-order kinetic models were 0.988 and 0.990, respectively, which fitted the phosphate adsorption process of MgBC600. Phosphate adsorption by MgBC600 was a spontaneous and endothermic process. The adsorption mechanism study showed that phosphate adsorption was controlled by the formation and electrostatic attraction of MgHPO4. In addition, 98% of chemically adsorbed phosphate was released after regeneration. Using phosphate-adsorbed MgBC600 as a soil amendment, Arabidopsis thaliana was 1.47 times higher than that in the biochar-only group, demonstrating that this is a promising strategy for enhancing phosphate adsorption efficiency and adsorbent recycling.

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.

Enhanced phosphate removal from water by hydrated neodymium oxide-based nanocomposite: Performance, mechanism, and validation

Phosphorus (P) control has been recognized as an imperative task to mitigate water eutrophication and settle the imminent shortage of P resources. Despite intensive effort put into this matter, it is still generally challenging for the current methods to remove and even potentially recover phosphorus (as phosphate) from complicated water matrices. To this end, we proposed a novel nanocomposite via coupling polystyrene anion exchanger (PsAX) with hydrated neodymium oxide (HNdO) nanoparticle for selective removal of phosphate. The developed nanocomposite, i.e., HNdO-PsAX, exhibited quite stable and efficient phosphate adsorption over a wide pH range of 3.0–10.0 with the maximum adsorption capacity as 85.4 mg P/g. It also showed satisfied anti-interference against various competing substances; notably, HNdO-PsAX obviously outperformed Phoslock, a commercial lanthanum-based adsorbent exclusively for phosphate sequestration, particularly under the interference of bicarbonate and humic acid, which were admitted as the paralyzing factors for Phoslock. The superior affinity of HNdO-PsAX towards phosphate, driven by the specific Nd-P inner-sphere complexation as evidenced by XPS, FT-IR, and the lattice evolution of HNdO nanoparticle, renders the nanocomposite eminently suitable for sequestrating trace phosphate. Fixed-bed treatment validated that HNdO-PsAX was capable of treating ∼11,800 bed volume of a simulated wastewater (from 2.0 to below 0.5 mg P/L), approximately 12 times higher than that of the previously reported Fe-based nanocomposite (HFO-PsAX, ∼ 900 BV); also, a satisfactory outcome in treating authentic municipal wastewater by HNdO-PsAX and the feasibility of regenerating the exhausted one by a binary NaOH-NaCl solution were recognized. This work provides a new potion of enhanced phosphorous control for surface water and wastewater.

Efficient phosphate adsorption by a composite composed of Mg6Al2(CO3)(OH)16·4H2O LDH and Chitosan: kinetic, thermodynamic, desorption, and characterization studies

A composite composed of Mg6Al2(CO3)(OH)16·4H2O Layered Double Hydroxide (Mg-Al-CO3 LDH) and chitosan was synthesized and used as an adsorbent for phosphate removal from aqueous solutions. The composite adsorption capacity (106.3 mg(PO4)/g) was about twice higher than its constituents (chitosan 45.2 mg(PO4)/g and Mg-Al-CO3 LDH 54.9 mg(PO4)/g). Kinetic, equilibrium, thermodynamic, and desorption studies were performed, and the adsorbent was characterized before and after adsorption experiments by scanning electron microscopy and energy dispersive spectrometry, X-ray diffraction, Fourier transform infrared, and Brunauer-Emmett-Teller analyses. The results showed that the composite has a similar structure to Mg-Al-CO3 LDH, with an initial surface area of 28.47 m2/g, and satisfactory phosphate adsorption. The phosphate removal by the composite was favored at slightly acid conditions (pHZCP = 6.5 ± 0.3) at room temperature and was better fitted by the pseudo-second-order kinetic model (R2 = 0.98) and Freundlich isotherm model (R2 = 0.98). This indicates a favorable process occurring with a multilayer covering a heterogeneous surface and an adsorption rate limited by forces acting by exchanging or sharing electrons. In addition, thermodynamic data showed a spontaneous and exothermic (ΔH = -5.77 kJ/mol) process, with positive entropy (ΔS = 12.77 kJ/mol·K). After the adsorption experiments, the surface area of the adsorbent was 81.70 m2/g, which together with other results indicates that the high phosphate adsorption capacity presented by the composite may have been influenced by the partial dissolution of the adsorbent followed by its reprecipitation. The loaded composite was feasible (65.9 %) to be desorbed by a sodium hydroxide solution (NaOH, pH 12 ± 0.2) after 30 min of the experiment. The results emphasized that the Mg-Al-CO3 LDH/Chitosan composite was efficient in phosphate removal and could be successfully used for this purpose.

Lanthanum modified chitosan-attapulgite composite for phosphate removal from water: Performance, mechanisms and applicability

A novel lanthanum-modified-chitosan-attapulgite (La-CTS-ATP) composite with efficient adsorption of phosphate in water was prepared and characterized. The adsorption properties were investigated by adsorption kinetics, adsorption isotherms and thermodynamics. An orthogonal design test was used to explore the optimal preparation conditions of La-CTS-ATP. Various characterizations exhibited the successful modification of lanthanum and the effective adsorption of phosphate. The batch experiments showed that La-CTS-ATP exhibited excellent stability within pH range of 4–10 and the disturbance of co-existing substances (Cl−, NO3−, HCO3−, SO42−). Chemisorption played the main role in phosphate adsorption from kinetic studies. Isotherm studies illustrated monolayer uptake of adsorbents onto the adsorbent, and the maximum adsorption capacity was 102.90 mg/g, much higher than other La-based adsorbents. The reaction process was spontaneous (ΔG < 0), exothermic (ΔH < 0) and disordered (ΔS > 0) from thermodynamic analysis. The excellent reusability of La-CTS-ATP was investigated, after five cycles, the phosphate removal rate and desorption rates were 72.93 % and 77.44 %, respectively. The dynamic adsorption experiments showed that the faster the flow rate, the shorter the time for La-CTS-ATP to get saturation, and the maximum adsorption capacity was slightly reduced. The surface precipitation, electrostatic attraction, and ligand exchange were the main mechanisms affecting its adsorption behavior. The adsorbent exhibited excellent effectiveness in real wastewater (breeding wastewater and domestic wastewater). In this study, a novel and effective adsorbent for phosphorus removal was produced in contaminated water, and the analysis of the adsorption process of the system provides new insights for related research.

Converting Chrysotile Nanotubes into Magnesium Oxide and Hydroxide Using Lanthanum Oxycarbonate Hybridization and Alkaline Treatment for Efficient Phosphate Adsorption

Magnesium oxide and hydroxide nanomaterials comprise a class of promising advanced functional metal nanomaterials whose use in environmental and material applications is increasing. Several strategies to synthesize these nanomaterials have been described but are unsustainable and uneconomic. This work reports on a processing strategy that turns natural magnesium-rich chrysotile into magnesium oxide and hydroxide nanoparticles via nanoparticle hybridization and an alkaline process while enabling La-based nanoparticles to coat the chrysotile nanotube surfaces. The adsorbent's resulting hybrid nanostructure had an outstanding capacity for phosphate uptake (135.2 mg P g-1) and enhanced regeneration performance. Furthermore, the adsorbent featured wide applicability with respect to the coexistence of competitive anions and a broad range of pH conditions, and its high-performance phosphate removal from sewage effluent was also demonstrated. Spectroscopic and microscopic analyses revealed the scavenging ability of phosphate by the La-based and Mg-based nanoparticles and the multiple capture mechanisms involved, including surface complexation and ion exchange. This proposed approach expands chrysotile's potential use as a magnesium-rich nanomaterial and harbors great promise for the removal of pollutants in a variety of real-world settings.

Highly efficient P uptake by Fe3O4 loaded amorphous Zr-La (carbonate) oxides: Electrostatic attraction, inner-sphere complexation and oxygen vacancies acceleration effect

Bimetallic oxides composites have received an increasing attention as promising adsorbents for aqueous phosphate (P) removal in recent years. In this study, a novel magnetic composite MZLCO was prepared by hybridizing amorphous Zr-La (carbonate) oxides (ZLCO) with nano-Fe3O4 through a one-pot solvothermal method for efficient phosphate adsorption. Our optimum sample of MZLCO-45 exhibited a high Langmuir maximum adsorption capacity of 96.16 mg P/g and performed well even at low phosphate concentration. The phosphate adsorption kinetics by MZLCO-45 fitted well with the pseudo-second-order model, and the adsorption capacity could reach 79% of the ultimate value within the first 60 min. The phosphate adsorption process was highly pH-dependent, and MZLCO-45 performed well over a wide pH range of 2.0-8.0. Moreover, MZLCO-45 showed a strong selectivity to phosphate in the presence of competing ions (Cl−, NO3−, SO42−, HCO3−, Ca2+, and Mg2+) and a good reusability using the eluent of NaOH/NaCl mixture, then 64% adsorption capacity remained after ten recycles. The initial 2.0 mg P/L in municipal wastewater and surface water could be efficiently reduced to below 0.1mg P/L by 0.07 g/L MZLCO-45, and the phosphate removal efficiencies were 95.7% and 96.21%, respectively. Phosphate adsorption mechanisms by MZLCO-45 could be attributed to electrostatic attraction and the inner-sphere complexation via ligand exchange forming Zr/La-O-P, -OH and CO32− groups on MZLCO-45 surface played important roles in the ligand exchange process. The existence of oxygen vacancies could accelerate the phosphate absorption rate of the MZLCO-45 composites.

Lanthanum Hybridized with Fe3o4 For Efficient Phosphate Adsorption: Synthesis, Characterization, and Phosphorus Enrichment

Lanthanum Hybridized with Fe3o4 For Efficient Phosphate Adsorption: Synthesis, Characterization, and Phosphorus Enrichment

Ca2+ induced 3D porous MXene gel for continuous removal of phosphate and uranium

Three-dimensional (3D) porous MXene gel (MXene-Ca) was synthesized through a fast gelation of Ti3C2Tx MXene nanosheets initiated by calcium ions. The MXene-Ca showed efficient phosphate adsorption ability through the strong chemical reaction between Ca2+ and phosphate with a fast adsorption equilibrium (within 2 min). Furthermore, the recovered P/MXene-Ca gel after phosphate sorption could be used for adsorption of uranium in aqueous solution. Various analysis including SEM, TEM, XRD, XPS, FT-IR, BET surface area and zeta potential were carried out to fully characterize the materials. Increased specific surface area of the 3D porous structure and the formation of newly active adsorption sites of hydroxyapatite in P/MXene-Ca gel, are two main factors promoting the removal of U(VI). The maximum adsorption capacity was 823.6 mg/g at 298 K by Langmuir isotherm model. Kinetic studies disclosed that the of U(VI) followed the major chemical adsorption process. Overall results from batch experiments, leaching experiments, and characterizations demonstrated that the main mechanisms of the U(VI) removal by P/MXene-Ca including chemical adsorption on hydroxyapatite via dissolution precipitation and surface complexation with the oxygen-containing functional groups of MXene.

Highly regenerative and efficient adsorption of phosphate by restructuring natural palygorskite clay via alkaline activation and co-calcination.

Herein, we present a new strategy to create a highly regenerative and efficient phosphate adsorbent based on activating natural palygorskite structures. Both the regeneration via alkaline activation and synthesis via co-calcination restructured the palygorskite and created adsorptive metal oxides. The phosphate adsorbent exhibits excellent regeneration performance with high removal capacity.

Exploratory study of removing nutrients from aqueous environments employing a green synthesised nano zero-valent iron

ABSTRACT This study explores the green synthesis of nano zero-valent iron (nZVI) extracted from the peel of selected waste fruits: banana (BP), mango (MP), and pomegranate (GP), for the removal of nutrients from aqueous environments. The extract was prepared by heating de-ionised water at 60°C for 5 min, adding a reducing and a stabilising agent, FeCl3, then stirring with a N2 gas flush solution to form iron nanoparticles, with a final drying step under N2 conditions. Using a variety of characterisation techniques, it was determined that nZVI particles were successfully synthesised via the reduction of iron (III) to iron (0) and stabilised by the presence of phenolic compounds in the extract. The removal of 20 mg/L nutrients from an aqueous solution carried out using the nZVIs resulted in nitrate removal of 92% (nZVI-GP), 88% (nZVI-BP), and 72% (nZVI-MP) within 5 min, whereas ∼98% phosphate was removed by all three nZVIs within 60 min. The aging effect was also tested. Aging the nZVIs for >20 days resulted in less efficient phosphate adsorption after exposure for 250 min; ∼70% phosphate removal was achieved using the nZVIs under these conditions. The mechanisms and pathways of nitrate reduction, including the adsorption of phosphate by nZVI were demonstrated, and discussed. Leachability tests of the phosphate-loaded nZVIs revealed that 10%, 28%, and 48% phosphate was released from the nZVI-GP, nZVI-BP, and nZVI-MP particles, respectively. Using waste fruit is, therefore, a viable and sustainable alternative to the traditional sodium borohydride method to produce nZVIs for environmental application.

Novel talc encapsulated lanthanum alginate hydrogel for efficient phosphate adsorption and fixation

In the present work, talc (a low-cost clay) encapsulated salts alginate (TAL) beads were synthesized by cross-linking with lanthanum ion and tested for phosphate adsorption. Multiple methods were applied for the characterization of composites. The combined effect of talc and lanthanum improved phosphate removal performance of TAL beads. Factors such as talc content, La3+ concentration, adsorbent dosage, pH, co-existing ions (Cl−, NO3− and SO42−) were studied in batch experiments. The optimized TAL-7 beads exhibited satisfactory selectivity towards phosphate in the coexistence of competing anions and could remain efficient phosphate removal in the pH range of 4–6. The phosphate removal efficiency reached to 95% with a maximum uptake of 16.4 mg P/g obtained at the optimal pH 4. Further experiments suggested that Langmuir isotherm model and the pseudo-second-order kinetic model could well describe the phosphate adsorption process of TAL-7 beads. Moreover, TAL-7 beads exhibited superior phosphate fixation performance in the long-term experiment. The results from adsorption experiment and characterization analysis demonstrated that TAL-7 beads could be a cost-effective and promising biosorbent for phosphate adsorption and fixation in the aqueous environment.

Phosphate removal using free-standing functionalized mesoporous silica films with excellent recyclability

Abstract The fabrication of a novel adsorbent with biomass as template is a kind of effective and economical means to prevent the accelerated phenomenon of eutrophication. In this article, lanthanum(III)-coordinated amino-functional groups (La-EDA) anchored into free-standing mesoporous silica films to capture phosphate for the first time. The as-prepared modified free-standing inorganic/organic silica films (La-EDA-MSF) presented an outstanding adsorption property towards phosphate even at solution with high concentration of competing anions. The pH result manifested that the La-EDA-MSF could effectively capture phosphate over a wide pH range between 3 and 7. The reusability experiments indicated that no apparent adsorption capacity loss was observed compared with any other adsorbents. For the practical application, the phosphate absorption in environment sample by the as-prepared films was also evaluated and 98.35% of the phosphate could be removed by La-EDA-MSF in 1 h. In addition, the mechanism of phosphate absorption by this novel inorganic/organic silica film absorbent was also proposed. In general, findings in this paper could push forward the development of novel hybrid silica film adsorbent for application in rapid and efficient phosphate adsorption from the wastewater.

Preparation of polyaminated Fe3O4@chitosan core-shell magnetic nanoparticles for efficient adsorption of phosphate in aqueous solutions

In this study, novel polyethylenimine (PEI)-grafted chitosan (CS) core-shell (called as Fe3O4/CS/PEI) magnetic nanoparticles were synthesized and applied for adsorbing phosphate in water. The magnetic and physicochemical properties of as-synthesized nanoparticles were first analyzed by means of a superconducting quantum interference device, X-ray diffractometer, X-ray photoelectron spectroscope, Fourier-transform infrared spectroscope, transmission electron microscope, zeta potential analyzer, and nitrogen sorptiometer. The followed experiments indicated that the amount of phosphate adsorbed increased with increasing equilibrium pH to near 4.0 and then decreased when the pH was further increased. The adsorption isotherms of phosphate on Fe3O4/CS/PEI particles were well fit by the Langmuir equation, and its maximum adsorption was 48.2mgg−1 at an equilibrium pH of 3.0 and 25°C. The primary mechanism for phosphate adsorption on Fe3O4/CS/PEI particles was electrostatic attraction. The preferential adsorption of phosphate in the presence of other excess anions including chloride, nitrate, carbonate, and sulfate was presented. Under the conditions studied, more than 90% of phosphate was desorbed from the laden Fe3O4/CS/PEI particles by 0.05mol L−1 of NaOH solution. The remained adsorption efficiency obtained in the five-cycle reusability tests has demonstrated the promising application potential of Fe3O4/CS/PEI particles.

Efficient Phosphate Sequestration in Waters by the Unique Hierarchical 3D Artemia Egg Shell Supported Nano-Mg(OH)2 Composite and Sequenced Potential Application in Slow Release Fertilizer

Artemia nauplii are important bait or food sources in aquaculture, but the egg shells after incubation are always subjected to discarding as natural wastes; therefore, application and utilization of the Artemia egg-shell wastes will be an important issue. Herein, we reported a new hybrid biomaterial by encapsulating nano-Mg(OH)2 onto discarded Artemia egg shells for phosphate sequestration enhancement. The unique hierarchically 3D-layered structure of Artemia egg shells can endow well-defined nano-Mg(OH)2 morphology and efficient phosphate adsorption performances. The results of the final hybrid biomaterial exhibit a wide pH dependent sorption process, strong affinity toward phosphate removal, and large sorption capacity. Moreover, the exhausted adsorbent shell–Mg-P can be further utilized as slow-release fertilizer without regular chemical regeneration. The efficient slow-release behaviors of phosphorus onto Shell–Mg–P for 30 days indicated the potential applicability as fertilizers. Additionally, the ac...