PO4 Adsorption Research Articles

Charge regulated pH/NIR dual responsive nanoplatforms centered on cuproptosis for enhanced cancer theranostics

Multifunctional nanoplatforms capable of simultaneously executing multimodal therapy and imaging functions are of great potentials for cancer theranostics. We present an elegantly designed, easy-to-fabricate poly(acrylic acid)/mesoporous calcium phosphate/mesoporous copper phosphate nanosphere (PAA/mCaP/mCuP NS) with outstanding pH/NIR-sensitive multimodal-synergic anti-tumor effects. Optimal porous PAA NS scaffolds were prepared at room temperature by balancing the intra-PAA polymer and polymer-solvents Lennard-Jones potentials in a water:isopropyl alcohol (IPA) mix-solvent. Subsequent sponging of Ca2+ and Cu2+, and adsorption of PO43− to the PAA template were achieved through exquisite electrostatic interactions among ions and the ionizable PAA side-chain in an aqueous environment. This forms the basis for the tumor microenvironment pH-triggered release of Cu2+ to induce cuproptosis, as well as the photothermal effect originating from CuP, while Ca2+ can enhance the nanoplatform's biocompatibility and can damage mitochondria when overloaded. Lastly, PAA/mCaP/mCuP NSs still exhibit high drug loading efficiency for doxorubicin (DOX), enabling chemotherapy. Satisfactory anti-tumor effects of these modalities, along with their synergistic effects, were verified both in vitro and in vivo, with the NSs demonstrating good biodegradation in the latter. The fabricated NS itself holds great promise as an anti-tumor nanomedicine, and the thorough mechanical insights into NS formation may inspire the design of next-generation multifunctional nanoplatforms.

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.

Phosphate recovery from aqueous phase using novel zirconium-based adsorbent

This study aims to document the phosphate ion (PO43−) adsorption capacity of a novel zirconium-based adsorbent. The physicochemical properties of the adsorbent are investigated using an array of methods and metrics such as electron microscopy, X-ray diffraction, thermal analysis, specific surface area, pore volume, pH point of zero charge (pHpzc), and surface hydroxyl groups. The batch method is used to elucidate PO43− adsorption capacity. Results suggested that the adsorption of PO43− was based on an internal diffusion and a monolayer adsorption. We also clarified that the pH of the solution significantly impacted the adsorption. Moreover, the adsorbent shows the ability to not only adsorb but also desorb PO43− for at least five cycles, based on an adsorption mechanism that we document. These findings indicate that this adsorbent could serve as a major industrial PO43− adsorbent.

Adsorption of PO43−, Cd(II), Pb(II), Cu(II), As(III), and As(V) using the La-based and modified La-based metal–organic framework materials

Metal–organic framework (MOF) materials are novel adsorption materials for water treatment. In this study, La-MOF ({[La2(H2DHTPA)3(H2O)7]·4H2O}n, H4DHTPA denotes 2,5-dihydroxyterephthalic acid) was synthesized by a hydrothermal method. The material had a strong water stability, but its adsorption performance was weak and its processability was poor. K-La-MOF, with good processability, was obtained using a potassium permanganate oxidation modification method to modify the La-MOF. The results showed that the maximum adsorption capacity (qmax) of the La-MOF for PO43− was 72.19 mg/g, and the adsorption was monolayer chemical adsorption. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that P was adsorbed on the surface of the La-MOF material in the form of HPO42−. The adsorption properties of the K-La-MOF were also investigated. The results showed that the maximum adsorption capacities of the K-La-MOF for PO43−, Cd(II), Pb(II), Cu(II), As(III), and As(V) were 87.56, 37.08, 992.99, 190.51, 42.20, and 131.66 mg/g, respectively. The adsorption of PO43−, Cd(II), Cu(II), and As(III) by the K-La-MOF was determined to be monolayer chemisorption by fitting adsorption isotherm and kinetics models. The adsorption process of Pb(II) by the K-La-MOF involved both single-molecular-layer and lateral-multi-molecular-layer chemisorption. In contrast, the adsorption of As(V) by the K-La-MOF occurred through both monolayer chemical adsorption and pore physical adsorption. XRD and XPS analyses showed that P, Cd(II), Pb(II), Cu(II), As(III), and As(V) were adsorbed on the K-La-MOF in the forms of PO43−, CdO, PbO and Pb(OH)2, CuO, K3AsO4, and K4As2O7, respectively.

Kinetics of Struvite Crystals Formation through Adsorption and Crystallization Using Zeolite Modification

This study observed the formation of struvite crystals in wastewater using natural zeolite activated with Mg2+ ions. Mg2+ ions released from natural zeolite would react with PO43- and NH4+ ions from in wastewater to form struvite crystals. The results showed that at pH 8.5, the removal of PO43- and NH4+ ions was more effective using the modified zeolite than the natural zeolite. Adding 40 g/L Zeo-Mg (1) produced the best results, with PO43- (93.32%) and NH4 (40%) adsorption. Meanwhile, 40g/L Zeo-Mg (2) adsorbed 81% PO43- ions and 27.12% NH4+ ions. The eqilibrium time of all the treatments was 40 min. The results of observation through SEM, EDX, and FTIR showed that struvite crystals were formed on the zeolite surface. Kinetic models indicated that the mechanism of struvite formation on the surface of natural and modified zeolite was mainly chemisorption. Further calculations showed that the adsorption of PO43- and NH4+ ion followed the pseudo-first-order kinetic model.

Adsorption of PO43- by In-Situ Composite ZIF(Co)/Graphene

Adsorption of PO43- by In-Situ Composite ZIF(Co)/Graphene

Effects of surface defects and Bi2 pollution on adsorption of Po on Ag surface

During the operation of accelerator-driver systems, hazardous polonium isotopes are produced and their release affects the safety of the nuclear reactors. Reliable filter systems have been proposed to be developed and silver has been studied as one of candidate filter materials. In this work, the adsorption of atomic polonium on defective silver surface is calculated using first principles and strongly chemisorption was obtained. Vacancy on Ag (100), Ag (110), Ag (111) surfaces and hollow site at the step edge of Ag (211) surface are preferred Po adsorption sites. Effect of Bi2 molecule pollution on adsorption of Po is further considered. The result shows that the existence of Bi2 molecule reduces the capture ability of silver to Po, but strong adsorption was still obtained on the surfaces.

Synthesis of α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposite for effective removal of phosphate from water

AbstractA novel α‐manganese dioxide/β‐dicalcium silicate (α‐MnO2/β‐C2S) nanocomposite was synthesized for adsorption of phosphate ions from water to inhibit eutrophication. The adsorption rate constants (k2) of α‐MnO2/β‐C2S nanocomposite are higher than those of bare α‐MnO2 and β‐C2S revealing an increased adsorption rate in composite materials. The higher adsorption capacity of nanocomposites results from relatively larger pores. The phosphate sorption process obeys the pseudo‐second‐order kinetic model well and is likely governed by chemisorption. The equilibrium removal capacities of α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposite were found to be 25, 34.48, and 52.63 mg/g, respectively, which are very close to experimental values. Adsorption of PO43− onto adsorbents could be favorably described by the Langmuir model. D‐R isotherm model fitting showed physical adsorption by β‐C2S and α‐MnO2/β‐C2S nanocomposites and chemisorption on α‐MnO2. The maximum adsorption capacities (qm) of the adsorbents calculated from the Langmuir model were 28.58, 44.03, and 63.65 mg/g α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposites respectively. The thermodynamic parameters showed that the adsorption process occurs spontaneously with an exothermic nature and a decrease in randomness. The presence of coexisting Cl− anions decreases the adsorption capacity.

Application of Box-Behnken Design to Optimize Phosphate Adsorption Conditions from Water onto Novel Adsorbent CS-ZL/ZrO/Fe3O4: Characterization, Equilibrium, Isotherm, Kinetic, and Desorption Studies.

Phosphate (PO43-) is an essential nutrient in agriculture; however, it is hazardous to the environment if discharged in excess as in wastewater discharge and runoff from agriculture. Moreover, the stability of chitosan under acidic conditions remains a concern. To address these problems, CS-ZL/ZrO/Fe3O4 was synthesized using a crosslinking method as a novel adsorbent for the removal of phosphate (PO43-) from water and to increase the stability of chitosan. The response surface methodology (RSM) with a Box-Behnken design (BBD)-based analysis of variance (ANOVA) was implemented. The ANOVA results clearly showed that the adsorption of PO43- onto CS-ZL/ZrO/Fe3O4 was significant (p ≤ 0.05), with good mechanical stability. pH, dosage, and time were the three most important factors for the removal of PO43-. Freundlich isotherm and pseudo-second-order kinetic models generated the best equivalents for PO43- adsorption. The presence of coexisting ions for PO43- removal was also studied. The results indicated no significant effect on PO43- removal (p ≤ 0.05). After adsorption, PO43- was easily released by 1 M NaOH, reaching 95.77% and exhibiting a good capability over three cycles. Thus, this concept is effective for increasing the stability of chitosan and is an alternative adsorbent for the removal of PO43- from water.

Adsorption of PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) using a carbonised Mn-based metal–organic framework

Metal–organic frameworks (MOFs) are adsorbents suitable for water treatment. However, they are often water soluble and poorly processible, limiting their industrial applications. This study aims to develop a carbonized MOFs with high adsorption performance based on MOFs. Here, we report the production of Mn-MOF [Mn(DMF)2(H2DHTPA)]n (where DMF is N,N-dimethylformamide and H4DHTPA is 2,5-dihydroxyterephthalic acid) via a solvothermal method. This MOF shows good adsorption performance for various ions but dissolves easily in water. However, Mn-MOF-500 which was obtained by carbonising Mn-MOF at 500 °C shows high water stability. Thus, the adsorption properties of Mn-MOF-500 were investigated, revealing adsorption capacities for PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) of 126.66, 88.46, 356.21, 146.92, 51.28, and 166.10 mg/g, respectively. Based on the adsorption isotherms and the adsorption kinetics, the adsorption of PO43-, Cd(II), and As(III) occurs via monolayer chemisorption, whereas that of Pb(II), Cu(II), and As(V) occurs via monolayer chemisorption and physisorption in pores. X-ray diffractometry and X-ray photoelectron spectroscopy analysis showed that P, Cd(II), Pb(II), Cu(II), As(III), and As(V) were adsorbed on Mn-MOF-500 as PO43-, Cd(OH)2, PbO and Pb(OH)2, Cu(OH)2, Mn3(AsO3)2, and MnHAsO4, respectively.

Screening redox stability of iron rich by-products for effective phosphate immobilisation in freshwater sediments

Iron (Fe) rich by-products can be added to lake or river sediments to immobilise phosphate (PO4) and lower eutrophication risks. These Fe materials differ in mineralogy and specific surface area, hence differing in PO4 sorption capacity and stability under reducing conditions. This study was set up to identify key properties of these amendments in their capacity to immobilise PO4 in sediments. Eleven Fe rich by-products, collected from drinking water treatment plants and acid mine drainage, were characterised. The PO4 adsorption to these by-products was first determined under aerobic conditions and the solid-liquid distribution coefficient KD for PO4 correlated strongly to oxalate extractable Fe content. A static sediment-water incubation test was subsequently used to evaluate the redox stability of these by-products. The reductive processes gradually released Fe to solution and more Fe was release from the amended than from the control sediments. The total Fe release to solution was positively related to ascorbate reducible Fe fractions in the by-products, suggesting that such fractions indicate potential loss of P retention capacity on the long term. The final PO4 concentration in the overlying water was 5.6 mg P L−1 in the control and was successfully lowered by factor 30–420 depending on the by-product. The factor by which solution PO4 was reduced in Fe treatments increased with increasing KD determined under aerobic conditions. This study suggests that efficient by-products to trap P in sediments are characterised by a high oxalate Fe content and a low reducible Fe fraction.

Adsorption of Phosphate and Ammonium on Waste Building Sludge.

Two selected waste building sludges (WBS) were used in this study: (i) sludge from the production and processing of prestressed concrete pillars (B) and (ii) sludge from the production of technical stone (TS). The materials were used in their original and Fe-modified forms (BFe/TSFe) for the adsorption of NH4+ and PO43- from contaminated waters. The experiments were performed on a model solution simulating real wastewater with a concentration of 1.7 mmol·L-1 (NH4+) and 0.2 mmol·L-1 (PO43-). The adsorption of PO43- had a high efficiency (>99%) on B, BFe and TSFe, while for TS, the adsorption of PO43- was futile due to the high content of available P in the raw TS. The adsorption of NH4+ on all sorbents (B/BFe, TS/TSFe) had a lower efficiency (<60%), while TS proved to be the most effective. Leaching tests were performed according to the CSN EN 12457 standard for B/BFe and TS/TSFe before and after NH4+ and PO43- sorption when the contents of these ions in the leachates were affected by adsorption experiments in the cases of B and TS. For BFe and TSFe, the ion content in the leachates before and after the adsorption experiments was similar.

Development of aerated concrete waste/white cement composite for phosphate adsorption from aqueous solutions: Characterization and modeling studies

Adsorbing phosphate (PO4−3) from aqueous solutions onto concrete-based construction waste represents a low-cost, nontoxic, and sustainable technique. The novelty of this paper focuses on the adsorption and desorption of PO4−3 from aqueous solutions using autoclaved concrete (AC) chemically activated with white cement (AAC), representing an innovative adsorbent. Pseudo-second-order model better represent adsorption for AC (0.29 mg g−1; pH 6.35) and AAC (0.54 mg g−1; pH 6.53). The experimental data adjusted better with Freundlich and Langmuir models for AC (8.87 mg g−1) and AAC (3.90 mg g−1), suggesting physisorption and chemisorption, respectively. The presence of calcite could promote ligand exchange onto adsorbent surfaces. For desorption, pseudo-first-order model better explained for AC (0.19 mg g−1) and pseudo-second-order model for AAC (0.39 mg g−1). Sips model better fitted the equilibrium data (0.45 mg g−1 AC; 1.97 mg g−1 AAC), related to ionic exchange and electrostatic repulsion. Phosphate adsorption tends to be more reversible in AC. The chemical activation with white cement enhanced the phosphate removal and recovery by the alternative low-cost autoclaved aerated concrete. Finally, AC and AAC presented potential of reducing phosphate with 64.7% and 92.6% for raw wastewater and 83.1% and 84.8% for primary-treated effluent of a corn flour processing, respectively.

Study of simultaneous adsorption of ammonium and phosphate in waters by La-F4A zeolites prepared from spent FCC catalyst

The problem of resource disposal of massive spent fluid catalytic catalyst needs to be solved urgently. Thus an environmentally friendly, highly efficient and economical cost adsorbent used for nitrogen and phosphorus removal was prepared from spent fluid catalytic catalyst. A novel 4A zeolite adsorbent loaded with lanthanum hydroxide (La-F4A) was prepared by acid leaching pretreatment, alkali fusion roasting hydrothermal and co-precipitation method. And use La-F4A in the study of simultaneous adsorption of ammonia-nitrogen and phosphorus in water. Adsorption experiments were carried out under the condition that the primordial concentrations of PO4 and NH4+-N were respectively 1 &amp; 10mg/L. La-F4A has an adaptive adsorption ability on NH4+-N and PO4 in the pH range of 4-9. When the temperature is 298K, the dosage is 1.0 g/L, the contact time is 240 min, and test water pH=7, the maximum adsorption capacities for NH4+-N and PO4 are 7.64 mg/g and 0.93 mg/g respectively. The behaviours accord with the pseudo-second-order adsorption kinetic model. The adsorption of PO4 conforms to the Langmuir isotherm model while NH4+-N conforms to the Freundlich isotherm model. Coexisting anions have almost no effect on the adsorption of PO4, coexisting cations have different inhibitory effects on the adsorption of NH4+-N. After four desorption cycles, the removal efficiency of La-F4A for NH4+-N and PO4 was 77% and 93% of the initial capacity. There are both chemical adsorption and physical adsorption in the process. The ammonium removal mechanism is the ion exchange between NH4+ and Na+ in the framework, and the phosphate removal mechanism is the ligand exchange between PO4 and hydroxyl to form LaPO4. La-F4A is regarded to be an excellent adsorbent for ammonium and phosphate removal.

Retardation factors in controlling the transport of inorganic, organic, and particulate phosphorus in fluvo-aquic soil

Excessive application of fertilizers has caused a high load of phosphorus (P) in the North China Plain. The fate of P and its effects on aquatic ecosystems depend on its chemical speciation in soils. However, few studies systematically investigated the transport and retardation of different P species in the fluvo-aquic soil. In this study, the transport of inorganic P (orthophosphate, PO4), organic P (phytic acid, PA) and particulate P (hydroxyapatite nanoparticles, nHAP) in the fluvo-aquic soil were investigated by column experiments, and their retardation from major soil components such as kaolin, CaCO3, Al2O3, and goethite (GT) was also investigated by monitoring breakthrough curves and fitting transport models. The transport of P species in fluvo-aquic soil followed the order of PO4 > PA > nHAP. A high fraction of increased clay and mineral particle-associated P (P-E) was observed for PO4 and PA; while significant Ca-associated P (P-Ca) for nHAP. Under the experimental conditions, both CaCO3 and GT were the most influential factors for PO4, PA, and nHAP retention. Goethite strongly inhibited PO4 transport due to its high PO4 adsorption capacity, while CaCO3 strongly inhibited PA transport due to its strong association with PA under alkaline conditions. Both CaCO3 and GT can severely inhibit nHAP transport due to the favorable electrostatic conditions as well as the Ca2+ bridging effect. These results indicated that CaCO3 played a key role in regulating the retention of organic P and particulate P in the calcareous soil, and also suggested the important role of Fe (hydr)oxides in controlling the transport of inorganic P, which could out-compete that of CaCO3.

Interactions between microbial activity and bioturbation modes of benthic invertebrates determine nutrient releases from reservoir sediments

Abstract Bioturbating invertebrates play key roles in nutrient recycling from sediments to the water column in most lentic ecosystems. Nevertheless, the role of bioturbating fauna on nutrient cycling depends on complex interactions between their bioturbation modes and both the sedimentary conditions and the microbial activity occurring inside sediments. This study aims to evaluate the effect of different bioturbation modes by two invertebrate species (tubificid worm Tubifex tubifex and chironomid larvae of Chironomus plumosus), on the release of nutrients (NH4+, NO3−, and PO43−) from three different types of sediments characterised by distinct microbial activities and nutrient (N and P) contents. We expected that the influence of a bioturbation mode on nutrient fluxes was dependent on the microbial activity and organic matter processes occurring in sediments. Aquatic mesocosms were setup in the laboratory with three fauna treatments (i.e. without fauna, with tubificid worms, and with chironomid larvae) and three sediment types (collected in three reservoirs). The presence of bioturbating invertebrates increased PO43− concentrations into the water column (from 1.3‐ to 17‐fold higher concentrations) depending on the sediments tested. PO43− releases in the water column were positively linked to total P concentration and microbial activity in sediments. The influences of tubificid worms and chironomid larvae on PO43− releases into the water were not only due to their bioturbation modes but also depended on the interactions with P dynamics (e.g. adsorption of PO43− by iron oxides) at the water–sediment interface. The influence of fauna on the release of dissolved inorganic nitrogen (DIN) varied strongly among sediments due to the control of N cycling by microbial processes. In sediments characterised by the lowest microbial activity, DIN release from sediments to the water column was significantly stimulated by invertebrates (from 1.3‐ to 3.7‐fold higher). In contrast, no fauna effect was detected compared to controls in sediments characterised by the highest microbial activity. This study demonstrated that the influence of the bioturbation mode on nutrient (i.e. PO43− and DIN) dynamics at the water sediment interface was largely modulated by the intensity of microbial activity and biogeochemical processes occurring in sediments.

A new method for phosphate purification for oxygen isotope ratio analysis in freshwater and soil extracts using solid-phase extraction with zirconium-loaded resin.

Phosphate (PO4 ) oxygen isotope (δ18 OPO4 ) analysis is increasingly applied to elucidate phosphorus cycling. Due to its usefulness, analytical methods continue to be developed and improved to increase processing efficiency and applicability to various sample types. A new pretreatment procedure to obtain clean Ag3 PO4 using solid-phase extraction (SPE) with zirconium-loaded resin (ZrME), which can selectively adsorb PO4 , is presented and evaluated here. Our method comprises (1) PO4 concentration, (2) PO4 separation by SPE, (3) cation removal, (4) Cl- removal, and (5) formation of Ag3 PO4 . The method was tested by comparing the resulting δ18 OPO4 of KH2 PO4 reagent, soil extracts (NaHCO3 , NaOH, and HCl), freshwater, and seawater with data obtained using a conventional pretreatment method. PO4 recovery of our method ranged from 79.2% to 97.8% for KH2 PO4 , soil extracts, and freshwater. Although the recovery rate indicated incomplete desorption of PO4 from the ZrME columns, our method produced high-purity Ag3 PO4 and accurate δ18 OPO4 values (i.e., consistent with those obtained using conventional pretreatment methods). However, for seawater, the PO4 recovery was low (1.1%), probably due to the high concentrations of F- and SO4 2- which interfere with PO4 adsorption on the columns. Experiments indicate that the ZrME columns could be regenerated and used repeatedly at least three times. We demonstrated the utility of ZrME for purification of PO4 from freshwater and soil extracts for δ18 OPO4 analysis. Multiple samples could be processed in three days using this method, increasing sample throughput and potentially facilitating more widespread use of δ18 OPO4 analysis to deepen our understanding of phosphorus cycling in natural environments.

Adsorption of Phosphate and Nitrate Ions on Oxidic Substrates Prepared with a Variable-Charge Lithological Material

This work evaluates phosphate and nitrate ion adsorption from aqueous solutions on calcined adsorbent substrates of variable charge, prepared from three granulometric fractions of an oxidic lithological material. The adsorbent material was chemically characterized, and N2 gas adsorption (BET), X-ray diffraction, and DTA techniques were applied. The experimental conditions included the protonation of the beds with HCl and H2SO4 and the study of adsorption isotherms and kinetics. The lithological material was moderately acidic (pH 5) with very little solubility (electrical conductivity 0.013 dS m−1) and a low cation exchange capacity (53.67 cmol (+) kg−1). The protonation reaction was more efficient with HCl averaging 0.745 mmol versus 0.306 mmol with H2SO4. Likewise, the HCl-treated bed showed a better adsorption of PO4−3 ions (3.296 mg/100 g bed) compared to the H2SO4-treated bed (2.579 mg/100 g bed). The isotherms showed great affinity of the PO4−3 ions with the oxide surface, and the data fit satisfactorily to the Freundlich model, suggesting a specific type of adsorption, confirmed by the pseudo-second-order kinetic model. In contrast, the nitrate ions showed no affinity for the substrate (89.7 µg/100 g for the HCl-treated bed and 29.3 µg/100 g bed for the H2SO4-treated bed). Amphoteric iron and aluminum oxides of variable charges present in the lithological material studied allow for their use as adsorbent beds as an alternative technique to eliminate phosphates and other ions dissolved in natural water.

Studies on the removal of phosphate in water through adsorption using a novel Zn-MOF and its derived materials

A novel zinc-based metal–organic framework, {[Zn3(atz)2(pda)2]·2(H2O)}n (Zn-MOF; Hatz is 5-aminote-1H-terazole; H2pda is malonic acid), was prepared using the solvothermal method. Carbonization of the prepared Zn-MOF was conducted under elevated temperatures to investigate its phosphate adsorption performance. Through pre-adsorption experiments, the optimal carbonization temperature of 500 °C was determined, yielding Zn-MOF-500. Besides, multiple characterization methods were used to analyze the properties of Zn-MOF and Zn-MOF-500 materials before and after the adsorption of phosphate ions. The results showed that the BET surface area of Zn-MOF-500 was 18.57 m2/g, which was 16.37 times larger than that of the BET surface area of Zn-MOF. At 25 °C, Zn-MOF and Zn-MOF-500 exhibited an adsorption capacity of 123.44 and 226.07 mg/g, respectively. Based on the adsorption isotherms and the adsorption kinetics, the adsorption of PO43- occurs via monolayer. X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS) analysis showed that P was adsorbed on Zn-MOF and Zn-MOF-500 as the zinc hydrogen phosphate and zinc phosphate ions, respectively.

Polypyrrole/Magnetic/Tea Waste Composites for PO43− Ions Removal: Adsorption-Desorption, Kinetics, and Thermodynamics Studies

The polypyrrole (PPY/TW) and magnetic (MG/TW) composite with tea waste (TW) was prepared and used as an adsorbent for PO4 3− ions removal from aqueous media. The composite were characterized with SEM and FTIR techniques. Batch study was conducted to investigate the effect of different reaction parameters on the adsorption of PO4 3− ions. The native TW, PPY/TW, and MG/TW showed the PO4 3− ions removal of 7.2, 7.3, and 7.9 (mg/g), respectively, using 0.05 g adsorbent dose and 10 mg/L initial concentration of PO4 3− ions at pH of 6, 10, and 3, respectively, and equilibrium was reached in 90 min. Kinetics and isotherm models were employed on the PO4 3− ions adsorption data and PO4 3− ions adsorption followed the pseudo-second order kinetics, intraparticle diffusion, and Langmuir isotherm models. Thermodynamics analysis reveals an exothermic process and spontaneous adsorption of PO4 3− ions on the composites. Results revealed that the magnetic and polypyrrole composites with tea waste have auspicious potential as an adsorbent and this class of the composites can be utilized for the removal of PO4 3− ions from the effluents.