Phosphorus-containing Wastewater Research Articles

Utilizing Waste Biomass from Agricultural and Forestry Sustainable Resources: Biomass Conversion to Functional Adsorbent Material for Efficient Removal of Total Phosphate in Practical Water.

The promotion of the utilization of waste agricultural and forestry resources (AFRs) as a means of combating environmental pollution represents an advanced and necessary development approach with the potential to achieve sustainable development. In this work, an advanced adsorbent with a functional Mg-Al bimetallic layer was prepared using waste sawdust biomass (WSD) as a raw material. The layer serves as the primary active component for adsorbing total phosphate from both simulated and real wastewater. The hierarchical structure of the Mg-Al bimetallic hydroxide-modified waste sawdust biomass (MA@WSD) has an abundance of nanosheets on its surface, providing ample binding sites and an enhanced specific surface area of 175.99 m2/g. Under the optimal conditions, the maximum removal efficiency toward phosphate can reach 99.99%. The adsorption of phosphate by MA@WSD follows the pseudo-second order kinetic (PSOK) model, indicating that chemisorption is the rate-determining step. Moreover, the thermodynamic data demonstrate the spontaneous nature of the adsorption process, indicating the favorable characteristics of the developed material. The adsorption mechanism can be summarized as the collaboration of physical adsorption, electrostatic interaction, and chemical adsorption. The results of the regeneration process indicate that MA@WSD exhibits a retention of 50.3% of its initial adsorption performance following the fifth testing cycle, thereby suggesting its potential for comparable reusability. The MA@WSD performs well in adsorbing total phosphate in real river water, and the removal efficiency of MA@WSD is evidently superior to commercial activated carbon, which is at least 70% higher than that of the commercial activated carbon. Besides, the 5-time average removal efficiency toward total phosphate by MA@WSD is 62.9%, evidently higher than the 29.1% of commercially available activated carbon, indicating its potential as an alternative for treating phosphorus-containing wastewater. The research provides theoretical support for harmless treatment, resource utilization, carbon sequestration, and emission reduction of waste biomass.

Treating waste with waste: adsorption behavior and mechanism of phosphate in water by modified phosphogypsum biochar.

The use of green methods to treat industrial waste and waste reuse has become a key environmental issue. In order to achieve this goal, this study treated waste phosphogypsum (PG) and produced modified PG biochar to adsorb and remove phosphorus from PG leachate, so that the PG pollution problem was controlled. In this study, PG was modified with sodium carbonate (Na2CO3) to prepare a modified PG biochar that was used for the removal of phosphorus-containing wastewater. An X-ray diffraction (XRD) analysis of the modified PG revealed that the main component was calcium carbonate (CaCO3), and a suitable amount of modified PG could load calcium oxide (CaO) onto the biochar and improve its physical properties. The experimental results showed that the modified PG biochar had a maximum phosphorus adsorption capacity of 132mg/g. A further investigation of the mechanism of adsorption revealed the importance of electrostatic attraction and chemical precipitation, and it was found that the CaO in the modified PG biochar could effectively facilitate the conversion of phosphate to hydroxylapatite (Ca5(PO4)3OH) in water. The phosphorus removal rate from leachate obtained from a landfill containing PG was 99.38% for a specific dose of the modified PG biochar. In this study, a PG pollution control technology was developed to realize the goal of replacing waste with waste.

ZnO/PUF composites with a large capacity for phosphate adsorption: adsorption behavior and mechanism studies.

Phosphate is present in all kinds of industrial wastewater; how to remove it to meet the strict total phosphorus discharge standards is a challenge. This study used a one-step foaming technique to fill polyurethane foam (PUF) with ZnO, taking advantage of PUF's excellent features like its porous network, lightweight, hydrophilicity, and abundance of binding sites to create ZnO/PUF composites with high adsorption capacity and exceptional separation properties. The adsorption isotherms, kinetics, starting pH, and matrix impacts of ZnO/PUF composites on phosphate were examined in batch studies. The results showed that the composites had good adsorption performance for phosphate with a saturated adsorption capacity of 460.25mg/g. The quasi-secondary kinetic and Langmuir models could better describe the adsorption process, which belonged to the chemical adsorption of monomolecular layers. The composites' ability to treat phosphates in complicated waters was shown by their ability to retain a high adsorption capacity in the pH range of 3-6. In column experiments, the composite also maintains a good affinity for phosphate during dynamic adsorption. Multiple characterizations indicate that the adsorption mechanism is a combined effect of ligand exchange and electrostatic interactions. Therefore, this study provides valuable insights for practical phosphorus-containing wastewater treatment.

Removal mechanisms and metabolic responses of Chlorella pyrenoidosa to dissolved organic phosphorus

Microalgae-based biotechnology holds significant potential for addressing dual challenges of phosphorus removal and recovery from wastewater; however, the removal mechanism and metabolic adaptation of microalgae to dissolved organic phosphorus (DOP) are still unclear. This study investigated the removal mechanisms and metabolomic responses of the Chlorella pyrenoidosa to different DOP forms, including adenosine triphosphate (ATP), glucose-6-phosphate (G-6-P), and β-glycerophosphate (β-GP). The results showed C. pyrenoidosa could efficiently take up above 96% DOP through direct transport and post-hydrolysis pathways. The uptake of inorganic phosphorus (IP) followed pseudo first order kinetic model, while DOP followed pseudo second order kinetic model. Metabolite profiling revealed substantial alterations in central carbon metabolism depending on the DOP source. G-6-P upregulated glycolytic and TCA cycle intermediates, reflecting enhanced carbohydrates, amino acids and nucleotides biosynthesis. In contrast, ATP down-regulated carbohydrate and purine metabolism, inhibiting sustainable growth of microalgae. This study offers theoretical support for phosphorus-containing wastewater treatment using microalgae.

The Simultaneous Efficient Recovery of Ammonia Nitrogen and Phosphate Resources in the Form of Struvite: Optimization and Potential Applications for the Electrochemical Reduction of NO3.

In response to the need for improvement in the utilization of ammonium-rich solutions after the electrochemical reduction of nitrate (NO3--RR), this study combined phosphorus-containing wastewater and adopted the electrochemical precipitation method for the preparation of struvite (MAP) to simultaneously recover nitrogen and phosphorus resources. At a current density of 5 mA·cm-2 and an initial solution pH of 7.0, the recovery efficiencies for nitrogen and phosphorus can reach 47.15% and 88.66%, respectively. Under various experimental conditions, the generated struvite (MgNH4PO4·6H2O) exhibits a typical long prismatic structure. In solutions containing nitrate and nitrite, the coexisting ions have no significant effect on the final product, struvite. Finally, the characterization of the precipitate product by X-ray diffraction (XRD) revealed that its main component is struvite, with a high purity reaching 93.24%. Overall, this system can effectively recover ammonium nitrogen from the NO3--RR solution system after nitrate reduction, with certain application prospects for the recovery of ammonium nitrogen and phosphate.

Phosphate Removal Efficiency and Life Cycle Assessment of Different Anode Materials in Electrocoagulation Treatment of Wastewater

The excessive discharge of phosphorus-containing wastewater contributes to eutrophication, posing a serious threat to aquatic ecosystems. Therefore, methods such as electrocoagulation should be utilized to remove phosphorus from wastewater prior to discharging it into a water body. In this study, we aimed to determine the effectiveness of electrocoagulation in treating simulated phosphorus-containing wastewater under different parameters, including anode material (aluminum, iron, and magnesium), electrode distance (ED) (1, 2.5, and 4.5 cm), pH (3, 6, and 9), and current density (CD) (3, 6, and 9 mA/cm2). Additionally, three models of phosphate removal, the pseudo-first-order (PFO), pseudo-second-order (PSO), and Behnajady–Modirshahla–Ghanbery (BMG) models, were used to simulate the relationship between phosphate concentration and time in the electrocoagulation process using the three metals for phosphate removal. The experimental results showed that the aluminum system had the highest removal efficiency (90%) when energized for 20 min under a CD of 3 mA/cm2, followed by those of the iron (80%) and magnesium (35%) systems. Furthermore, a life cycle assessment (LCA) showed that the aluminum electrode system had a smaller environmental impact than the iron and magnesium electrode systems. Therefore, the aluminum electrode system is suitable for phosphorus removal from wastewater.

Synthesis of MgO-Coated Canna Biochar and Its Application in the Treatment of Wastewater Containing Phosphorus

In order to treat phosphorus-containing wastewater and realize the resource utilization of wetland plant residues, biochar was prepared by the pyrolysis of canna aquatic plant waste at 700 °C, and the adsorption characteristics of phosphorus by MgO-modified biochar (MBC) were explored. The main results are as follows: the adsorption capacity of the MBC was eight times that of unmodified biochar (BC), and the adsorption capacity was up to 244 mg/g. The isothermal adsorption data were consistent with the Langmuir equation, which indicates monolayer adsorption. The functional groups changed little before and after the modification, but a new diffraction peak appeared after the modification. Compared with the standard card, it was suggested that there were MgO crystals with a higher purity. SEM images showed that the BC had a smooth surface, an obvious pore structure, and a thin pore wall, while the MBC had a rough surface and a layered structure, which can provide more adsorption sites for phosphate adsorption. In addition, an XPS analysis showed that Mg3(PO4)2 crystals appeared on the surface of the MBC after adsorption. The mechanism analysis showed that MgO is an important substance for MBC to adsorb phosphorus, and electrostatic adsorption and complex precipitation play key roles. In the test to verify the removal of actual phosphorus-containing wastewater by MBC, it was found that the removal rates for wastewater with 2.06 mg/L and 199.8 mg/L of phosphorus by MBC were as high as 93.4–93.9% and 99.2–99.3%, respectively. MBC can be used as an efficient adsorbent for phosphorus removal.

Efficient Recovery of Phosphate from Water Media by Iron-Magnesium Functionalized Lignite: Adsorption Evaluation, Mechanism Revelation and Potential Application Exploration.

Selective phosphorus removal from aquatic media has become an ideal strategy to mitigate eutrophication and meet increasingly stringent discharge requirements. To achieve phosphorus control and resource utilization of low-calorific-value lignite, iron and magnesium salts were used to functionalize lignite, and iron-magnesium functionalized lignite (called IM@BC) was prepared for phosphate recovery from water media. The adsorption properties of IM@BC were systematically evaluated, especially the influence of ambient pH and co-existing ions. The kinetic, isothermal, and thermodynamic adsorption behaviors of IM@BC were analyzed. The adsorption mechanism was revealed by microscopic characterization. The potential application of phosphate-containing IM@BC (P-IM@BC) was explored. The results show that IM@BC has a strong phosphate adsorption capacity, and the maximum adsorption capacity is 226.22 mgP/g at pH = 3. Co-existing CO32- inhibits phosphate adsorption, while coexisting Ca2+ and Mg2+ enhance the effect. At the initial adsorption stage, the amount of phosphate adsorbed by IM@BC continues to increase, and the adsorption equilibrium state is gradually reached after 24 h. The adsorption process conforms to the pseudo-second-order kinetic model (PSO) and Langmuir isothermal adsorption model, and the adsorption process is mainly chemical adsorption. The phosphate absorption capacity is positively correlated with temperature (283.15 K~313.15 K), and the adsorption process is spontaneous, endothermic, and entropy-increasing. Its adsorption mechanism includes electrostatic attraction, ion exchange, surface precipitation, and coordination exchange. IM@BC can efficiently recover phosphate from actual phosphorus-containing wastewater with a recovery efficiency of up to 90%. P-IM@BC slowly releases phosphate from pH 3 to 11. Plant growth experiments showed that P-IM@BC could be used as a slow-release fertilizer to promote the root growth of cowpeas. The novelty of this work lies in the development of a highly efficient phosphate recovery adsorbent, which provides a feasible method of phosphorus control in water media and resource utilization of lignite.

Three-dimensional observation of porous materials prepared from iron tailings and their pore wall site adsorption function

Porous materials are widely used to treat phosphorus-containing wastewater due to their structural characteristics and loading site functionality. The use of iron tailings as a raw material during the preparation of these materials can effectively reduce production costs. In this study, a porous material was prepared according to a one-step method using solid waste iron tailings. High-temperature phase transition technology was used to construct crystallographic sites on the pore walls of the material to improve the phosphorus removal efficiency. The pore structure, pore wall characteristics, and internal crystal growth in the three-dimensional space of the material were characterized using X-ray microscopy (micro-CT) scanning, and the voxel data for the internal structural were analyzed. The results showed that the material had a clear internal skeletal structure, a uniform distribution of internal pores, and crystal phases in three-dimensional space. The pore ratio in the three-axis direction was greater than 50%, with connected pores accounting for more than 95% of the pores. The wall thickness distribution was uniform, but the pore size distribution and ellipticity ratio varied significantly due to the different pore structures and quantities. A connected structure was formed when the thin walls of adjacent pores ruptured, and there were magnesioferrite and hematite crystal sites with fractal growth in the pore wall framework. The adsorption capacity of the porous material for phosphorus pollutants was investigated using photometry, and the highest removal rate was found to be 68.13%. This analysis suggests that the presence of rough pore walls, a high specific surface area, and crystal sites within the pore walls enhance the adsorption performance of the material. Further research along this line could explore the potential of developing new low-cost materials for pollution treatment.

A Study on the Removal Characteristics and Mechanism of Phosphorus from Simulated Wastewater Using a Novel Modified Red-Mud-Based Adsorption Material

In this work, a common third-generation environmentally friendly quaternary ammonium salt disinfectant, dimethyl dioctadecyl ammonium chloride (DDAC), was used as the modifier to achieve one-step rapid preparation of the modified red-mud-based adsorption material under the condition of microwave assistance, and applied it to the adsorption phosphorus in solutions. After the process of this modification, the structure of the red mud (RM) was not changed, and the DDAC modification could provide more adsorption active sites. The adsorption experiments indicated that the novel modified red mud (NMRM) exhibited a good adsorption performance for phosphorus. The adsorption capability of NMRM for phosphorus was significantly enhanced, and was about eight times higher than that of the initial RM. The kinetics model of the pseudo-second-order, which implied that phosphorus was chemically adsorbed on the surface of the NMRM, could accurately represent the adsorption procedure of NMRM. The adsorption equilibrium of NMRM could be better depicted using the isotherm model of Freundlich. It was speculated that the ion exchange might be responsible for the adsorption mechanism of NMRM for phosphorus. Thus, the NMRM is a potential material for the treatment of phosphorus-containing wastewater due to its outstanding adsorption capability.

Application of common industrial solid waste in water treatment: a review.

Industrial solid waste has a wide range of impacts, and it is directly or indirectly related to land, atmosphere, water, and other resources. Industrial solid waste has a large amount of production, complex and diverse components and contains a variety of harmful substances. However, as industrial by-products, it also has a lot of available value. Industrial solid waste has been continuously studied in water treatment due to its special composition and porous and loose structure. It is known that there are few reviews of various industrial solid wastes in the field of wastewater treatment, and most of them only discuss single industrial solid waste. This paper aims to sort out the different studies on various solid wastes such as fly ash, red mud, wastewater sludge, blast furnace slag and steel slag in dyeing, heavy metal, and phosphorus-containing wastewater. Based on the modification of industrial solid waste and the preparation of composite materials, adsorbents, coagulants, catalysts, filtration membranes, geological polymers, and other materials with high adsorption properties for pollutants in wastewater were formed; the prospect and development of these materials in the field of wastewater were discussed, which provides some ideas for the mutual balance of environment and society. Meanwhile, some limitations of solid waste applications for wastewater treatment have been put forward, such as a lack of further researches about environment-friendly modification methods, application costs, the heavy metal leaching, and toxicity assessment of industrial solid waste.

Preparation of Fe/Zr bimetallic oxide beads and its performance and mechanism for advanced treatment of actual phosphorus-containing wastewater

Phosphorus removal by adsorption method has unique advantages in the wastewater treatment. The granulation and recycling performance of adsorbent are key factors restricting its practical application. To solve these problems, this study used an environmentally friendly binder to prepare Fe/Zr bimetallic oxide beads (Fe/Zr-Bead) with high mechanical strength and recyclability. The batch experiment results confirmed that the maximum adsorption capacity of Fe/Zr-Bead was 24.60 mg/g. During extended operational trials, the Fe/Zr-Bead-filled fixed-bed column enables unhindered flow of wastewater without blockages, effectively treating simulated wastewater with varying initial concentrations of phosphorus. Furthermore, Fe/Zr-Bead exhibits prominent performance in the treatment of real wastewater plant effluent, reducing the initial phosphorus concentration from 0.416 mg/L to below 0.05 mg/L. Even after undergoing 11 cycles of adsorption and desorption, the phosphorus removal capacity of Fe/Zr-Bead only decreased by 5.5 %. Moreover, the desorption solution, which contains phosphorus, can reach up to 57.93 mg/L, making it suitable for phosphorus resource recovery. Ligand exchange between hydroxyl oxygen and phosphorus was found the main mechanism for phosphorus removal by Fe/Zr-Bead. This study is valuable for overcoming the limitations of adsorption materials in practical applications and also provide practical and technical support for advancing phosphorus treatment in the future.

Efficient Treatment of Phosphorus-Containing Wastewater with Anion-Exchange Resin-Supported Nanohydrated Zirconia: Performance and Zr–P Structure Evolution Mechanism

Efficient Treatment of Phosphorus-Containing Wastewater with Anion-Exchange Resin-Supported Nanohydrated Zirconia: Performance and Zr–P Structure Evolution Mechanism

Adsorption of phosphate in water by La/Al bimetallic-organic frameworks-chitosan composite with wide adaptable pH range

The limited metal sites of monometallic MOFs and the high influence of pH limit their adsorption capacity. To solve these problems, La/Al bimetallic MOFs/chitosan composite was prepared by hydrothermal synthesis and impregnation methods and then characterized by XRD, FTIR, SEM, BET and XPS techniques. The doping of La has no obvious effect on the structure of Al-MOFs, but chitosan has greatly changed the structure of La/Al bimetallic MOFs. The phosphate adsorption of the composite was affected by La/Al molar ratio, chitosan/bimetallic MOFs mass ratio, temperature, phosphate initial concentration, adsorbent dosage, pH, and coexisting ions. The optimum molar ratio of La/Al and mass ratio of chitosan/bimetallic MOFs are 0.5:1 and 5.0%, respectively. The addition of La and chitosan can provide additional adsorption active sites, inhibit metal leaching, and enhance the phosphate adsorption performance, stability, and acid-alkali resistance of the composite. Its maximum adsorption capacity was 264.48 mg·g−1. Its phosphate removal efficiency is above 90% at pH= 3.0–9.0. The actual phosphorus-containing wastewater with 7.064 mg·L−1 PO43- and initial pH 7.4 can be treated to meet Chinese first-class effluent quality standard. La, Al, amino groups, and hydroxyl groups play an important role in the adsorption process of phosphate. When pH < pHpzc (4.99), phosphate is adsorbed by electrostatic gravitation between it and protonated positively charged amino and hydroxyl groups on La and Al, while when pH > pHpzc, phosphate is removed by ligand exchange between it and hydroxyl groups on La and Al. A stable, low-cost, and efficient bimetallic MOFs-based phosphate adsorbent was designed and prepared in this paper, and the results can provide reference for researchers in environmental chemical engineering.

Enhanced struvite (MgNH4PO4·6H2O) granulation and separation from synthetic wastewater using fluidized-bed crystallization (FBC) technology

Struvite (MgNH4PO4·6H2O) could be recovered from wastewater containing phosphorus and showed high potential as an alternative source of phosphorus fertilizer. A comparison of batch experiment and continuous crystallization processes was carried out using batch reactor and fluidized bed reactor (FBR) methods, respectively. The continuous crystallization processes for phosphorus granulation were conducted both in a seeded (FBC) and unseeded (FBHC) system. Various seed materials such as dolomite-(CaMg(CO3)2), CaHPO4, and SiO2 were applied as seed material in FBC. In the batch reactor, the operating parameters, including pH, [Mg]0/[P]0 molar ratio, and initial phosphorus concentration were first optimized. The effects of the coexisting ions (SO42−, Cl−, NO3−, Na+, K+, Ca2+) and organic pollutants (Ethylenediaminetetraacetic acid-EDTA, and Citric acid) on phosphorus-containing wastewater treatment were also examined. The hydraulic parameters of FBR (Fluidized-bed reactor), including effluent pHe, and cross-sectional surface loading (L, kg m−2 h−1) were investigated to recover phosphorus and ammonium as struvite pellets. Under optimum conditions (pHe 8.8, [Mg]0/[P]0 = 1.3/1, L = 2.4 kg-P m−2 h−1), FBC using dolomite as seed resulted in higher phosphorus removal efficiency than the FBHC system with total removal (TR) = 93.0 % and a crystallization ratio (CR) = 85.0 %. As confirmed by the XRD pattern, the solid products consist of magnesium ammonium phosphate (MgNH4PO4·6H2O) from both FBC and FBHC processes. The high crystallization ratio (CR = 85 %) and the recovery of crystal pellets (>1 mm) in the FBC process reduce the production of sludge compared to traditional chemical precipitation and FBHC processes.

Phosphorus biorecovery from wastewater contaminated with multiple nitrogen species by a bacterial consortium

Recovering finite and non-substitutable phosphorus from liquid waste streams through bio-mediated techniques has attracted increasing interest, but current approaches are incredibly dependent on ammonium. Herein, a process to recover phosphorus from wastewater under multiple nitrogen species conditions was developed. This study compared the effects of nitrogen species on the recovery of phosphorus resources by a bacterial consortium. It found that the consortium could not only efficiently utilize ammonium to enable phosphorus recovery but also utilize nitrate via dissimilatory nitrate reduction to ammonium (DNRA) to recover phosphorus. The characteristics of the generated phosphorus-bearing minerals, including magnesium phosphate and struvite, were evaluated. Furthermore, nitrogen loading positively influenced the stability of the bacterial community structure. The genus Acinetobacter was dominant under nitrate and ammonium conditions, with a relatively stable abundance of 89.01% and 88.54%, respectively. The finding may provide new insights into nutrient biorecovery from phosphorus-containing wastewater contaminated with multiple nitrogen species.

Research Progress on the Treatment of High-Concentration Nitrogen and Phosphorus Wastewater by Struvite Precipitation

Aiming at the problems of eutrophication of water bodies and the shortage of phosphorus resources, the struvite method for treating high-concentration nitrogen and phosphorus-containing wastewater has been widely used because of its high efficiency and low consumption. This paper summarizes the research progress on the treatment efficiency, influencing factors and stability of high concentration nitrogen and phosphorus mixed wastewater in recent years, and on this basis, the feasibility and development prospect of MAP method in the treatment of high concentration nitrogen and phosphorus wastewater are proposed.

Recovery of nitrogen and phosphorus in wastewater by red mud-modified biochar and its potential application

A large amount of wastewater containing nitrogen, phosphorus, and fluorine produces in the production of phosphate fertilizer. In this study, to simultaneously recover nitrogen and phosphorus from phosphorus-containing wastewater and realize the resource utilization of red mud and rape straw, red mud-modified rape straw biochar (RM/RSBC) was prepared by facile one step, and the physicochemical properties were characterized by Zeta potential, SEM-EDS, BET specific surface area (SSA), FTIR, XRD, and XPS. The adsorption performance and mechanisms of ammonium and phosphate onto RM/RSBC were explored through static, fixed-bed column adsorption, and practical wastewater experiments. The results showed that pH = 3.0 and 8.0 were favorable for the removal of phosphate and ammonium, respectively. The main adsorption mechanisms of ammonium and phosphate were the interaction between ammonium and surface functional groups and surface precipitation, respectively. The removal efficiencies of ammonium and phosphate by fixed-bed column adsorption mainly depended on the addition amount of RM/RSBC, the concentration of ammonium and phosphate, and the flow rate. The results of the germination experiment showed that adding > 0.5 wt% of RM/RSBC loaded with ammonium and phosphate promoted the growth of mung beans. This study shows that RM/RSBC can not only recover ammonium and phosphate in wastewater, but also realize the resource utilization of red mud and rape straw.

Utilization of cockle shell powder as an adsorbent to remove phosphorus-containing wastewater

The paper demonstrates the capability of using cockle shells as an adsorbent for phosphorus removal from simulated petrochemical wastewater, focusing on the actual condition of the petrochemical facultative pond. In this study, the physicochemical properties of shell powder were determined, such as the functional groups, surface morphology, crystalline structure, and surface area using FTIR, SEM, EDX, XRD, and BET. It was observed that the optimum conditions for effective phosphorus removal are under the presence of rotational speed (125 rpm), higher dosage (7 g/L), and larger surface area (smaller particle size) of the shell powder. Fine powder achieved up to 52.27% of phosphorus removal after 40 min compared to coarse powder which could only give 16.67% removal. Additionally, calcined shell powder demonstrated a higher phosphorus removal rate, i.e., up to 62.37%, compared to raw shell powders. The adsorption isotherm was studied using Langmuir and Freundlich models, but the isothermal data fit better for the Freundlich model (R2 = 0.9836). Overall, this study has successfully generated a greener and low-cost adsorbent.

Preparation and Phosphorus Removal Performance of Zr–La–Fe Ternary Composite Adsorbent Embedded with Sodium Alginate

Using single metal salts of zirconium, lanthanum, and iron as raw materials and sodium alginate as a cross-linking agent, a new composite adsorbent was prepared via the co-precipitation method and embedding immobilization technology, and its phosphorus adsorption performance in wastewater was evaluated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for characterization, and a 0.5 mol·L−1 sodium hydroxide solution was used to regenerate the adsorbent. The experimental results demonstrated that the adsorption rate reached 99.88% when the wastewater volume was 50 mL, the initial concentration of phosphorus-containing wastewater was 5 mg·L−1, the pH was 5, the dosage of composite adsorbent was 0.2 g, and the adsorption time was 200 min. The prepared adsorbent could reduce the initial phosphorus concentration of 5 mg·L−1 to 0.006 mg·L−1 in simulated wastewater, and from 4.17 mg·L−1 in urban sewage to undetected (&lt;0.01 mg·L−1), thus meeting the discharge requirements of the grade A standard of the Urban Sewage Treatment Plant Pollutant Discharge Standard (GB18918-2002). The adsorption process conformed to the Freundlich adsorption isothermal equation and quasi-second-order kinetic equation, and the adsorption reaction was exothermic and spontaneous. More importantly, after three lye regeneration tests, the removal rate of phosphorus in water remained above 68%, that is, the composite adsorbent could be reproducibly fabricated and recycled. The characterization results showed that the surface of the composite adsorbent was rough, with a complex pore structure. After phosphorus removal, the surface morphology of the composite adsorbent showed a similar honeycomb structure, with a P-H, P-O stretching vibration peak and a characteristic P2p peak. At the same time, the proportion of hydroxyl groups (M-OH) on the metal surface decreased after adsorption. Our findings thus demonstrate that the mechanism of phosphorus removal is mainly based on the coordination exchange reaction between phosphate and metal active sites and surface hydroxyl groups, resulting in the formation of granular phosphate deposits.