Efficient removal of phosphate from aqueous media using magnetic bimetallic lanthanum‑iron-modified sulfonylmethylated lignin biochar

La/Fe-Bimetallic-Modified Red Brick Powder for Phosphate Removal from Wastewater: Characterization, Adsorption, and Mechanism

The use of construction waste red brick powder (RBP) to prepare adsorbents for phosphate removal from wastewater represents a promising technology with substantial research potential. This study investigates the preparation of La-based magnetic red brick powder (La-Fe-RBP) via bimetallic modification to enhance its adsorption performance. The key characteristics, adsorption process, adsorption mechanism, and practical applications of the modified adsorbent were analyzed. The obtained results suggested that the underlying adsorption mechanism of La-Fe-RBP was best described by the Langmuir and pseudo-second-order kinetic models, which suggested that the adsorption mechanism was monolayer chemical adsorption. La-Fe-RBP exhibited rapid kinetics, achieving adsorption saturation in just 40 min, significantly faster than RBP (360 min). Additionally, isotherm experiments determined the highest theoretical adsorption capacity as 42.835 mg/g. More importantly, La-Fe-RBP exhibited efficient phosphate adsorption within a pH ranging from 3 to 8. Furthermore, La-Fe-RBP exhibited high selectivity for phosphate ions in the presence of coexisting ions (SO42-, NO3-, Cl-, HCO3-, Mg2+, and Ca2+), demonstrating its robustness and effectiveness in complex water conditions. FTIR and XPS analyses demonstrated that ligand exchange and electrostatic attraction were the primary mechanisms underlying phosphate adsorption by La-Fe-RBP. Domestic sewage treated with La-Fe-RBP met the Class IV surface water environmental quality standards in China. The findings of this study prove that the La-Fe-RBP composite material, characterized by high adsorption efficiency and strong selectivity, holds significant potential for removing phosphates from real wastewater.

Preparation of efficient and reusable lanthanum and iron co-modified soda residue for selective phosphate removal from domestic sewage

The selection of suitable raw materials as adsorbents is a key factor in effectively removing phosphorus from water. As an industrial by-product, soda residue exhibits high porosity and surface area, which can effectively adsorb pollutants. Magnetic lanthanum-iron soda residue (La-Fe-CSR) was synthesized using the co-precipitation method, and its characterization and mechanism for removing phosphate were thoroughly investigated. La-Fe-CSR exhibited good adsorption performance under acidic conditions (3 < pH < 7). A high concentration of HCO3- (100 mg/L) reduced the adsorption performance of La-Fe-CSR by 8.3% ± 2.5%, whereas the presence of other coexisting ions had a smaller impact. The adsorption of phosphate by La-Fe-CSR was controlled by chemisorption and reached saturation after approximately 120 min. The phosphate adsorption by La-Fe-CSR was significantly higher than that of soda residue (43.65 ± 3.39 mg/g), reaching 74.87 ± 2.46 mg/g. Ligand exchange and inner-sphere complexation constituted the primary mechanisms through which L-Fe-CSR removed phosphate. After 5 consecutive cycles, La-Fe-CSR maintained a phosphate removal efficiency of 74.5 ± 1.6%. It demonstrated good performance in removing total phosphorus from real domestic sewage, with a removal rate of 94.9 ± 0.5%. These research findings demonstrated that La-Fe-CSR held significant promise as a highly effective phosphate adsorbent in practical applications.

Towards zero-waste processes: Waste wool derivatives as phosphate adsorbents and auxiliaries for textiles' natural dyeing

The textile industry is a pillar of the manufacturing sector worldwide, but it still represents a significantly polluting production sector since it is energy-, water- and natural resource-intensive. Herein, waste wool that did not meet the technical requirements to be used for yarns and fabrics was recovered first to prepare materials for wastewater remediation, specifically for phosphate removal. The wool underwent an alkaline treatment, eventually saturated with FeCl3 and then left at room temperature or thermally treated to induce crosslinking/stabilisation, obtaining adsorbent panels. The main characterisation findings concerned the impact of alkaline treatment on morphology and structure; additionally, the samples with iron displayed a behaviour attributable to a crosslinking effect operated by Fe3+. Batch experiments showed that only samples with iron were efficient in phosphate adsorption, with a high removal percentage obtained in a wide pH range. Adsorption isotherms and kinetics were investigated, suggesting a complex system of interactions. Moreover, during the alkaline treatment necessary to prepare such wool-derived adsorbent panels, a significant amount of wool hydrolysates left in the solution was produced. These substances, in view of zero-waste procedures, were isolated and re-employed as dyeing auxiliaries. Preliminary results demonstrated that the wool hydrolysates enabled the dyeing of cotton with natural dyes, which is generally a tricky process.

Lanthanum-doped chitosan-based polyacrylamide double network hydrogels for adsorption of phosphorus from wastewater

Excessive phosphorus in aqueous solutions can cause eutrophication, which can harm aquatic organisms and pose a risk to the safety of drinking water for humans. The Chitosan/Polyacrylamide/Lanthanum (CS/PAM/La) hydrogel was designed to get rid of phosphate from aqueous solutions. La (III) was used to enhance the capacity of adsorption of CS. Polyacrylamide was used to enhance the mechanical properties of CS. The results showed that the adsorption capacity of CS/PAM/La hydrogel for phosphate was increased compared with that of CS. When pH of 5.0, the adsorption capacity was 80.07 mg-P/g. In addition, after five adsorption and desorption cycles, the adsorption efficiency remained above 90%. The mechanism of phosphate adsorption on CS/PAM/La material was analyzed using a mass transfer factor model (MTF) and the possible structure of CS/PAM/La hydrogel was calculated by density functional theory calculation (DFT). The application of CS/PAM/La composite hydrogel for removal of phosphate from actual wastewater was investigated, and the results met the requirement of national standard.

Machine learning-driven prediction of phosphorus removal performance of metal-modified biochar and optimization of preparation processes considering water quality management objectives

Developing an optimized and targeted design approach for metal-modified biochar based on water quality conditions and management is achievable through machine learning. This study leveraged machine learning to analyze experimental data on phosphate adsorption by metal-modified biochar from literature published in Web of Science. Using six machine learning models, the phosphate adsorption capacity of biochar and residual phosphate concentration were predicted. After hyperparameter optimization, the gradient boosting model exhibited superior training performance (R2 > 0.96). Metal load quantity, solid-liquid ratio, and pH were key factors influencing adsorption performance. Optimal preparation parameters indicated that Mg-modified biochar achieved the highest adsorption capacity (387-396 mg/g), while La-modified biochar displayed the lowest residual phosphate concentration (0 mg/L). The results of verification experiments based on optimized process parameters closely aligned with model predictions. This study introduces a new machine learning-based approach for tailoring biochar preparation processes considering different water quality management objectives.

In-situ preparation of lignin/Fe3O4 magnetic spheres as bifunctional material for the efficient removal of metal ions and methylene blue

In this paper, magnetic composite of lignin/Fe3O4 spheres were synthesized via a straightforward one-step in-situ solvothermal method showing good capacity for adsorbing heavy metal ions and dyes. The physicochemical properties of lignin/Fe3O4 spheres are analyzed using a range of techniques such as SEM, XRD, FTIR, VSM, TG, and BET. Lignin/Fe3O4 spheres exhibited high adsorption capacities of 100.00, 353.36 and 223.71 and 180.18 mg/g for Cu (II), Ni (II) and Cr (VI) metal ions and methylene blue (MB) with equilibrium attained within 60 min. After the recycling experiments, lignin/Fe3O4 spheres still possesses excellent superparamagnetic properties and displays high adsorption capacity. The lignin/Fe3O4 spheres are an efficient and continuous adsorbent to remove heavy metal ions of Cu (II), Ni (II), Cr (VI) and cationic dyes of methylene blue in wastewater, which proves the great potential in practical pollutants treatment applications for water systems.

Recent advances and future perspective on lignocellulose-based materials as adsorbents in diverse water treatment applications

The growing shortage of non-renewable resources and the burden of toxic pollutants in water have gradually become stumbling blocks in the path of sustainable human development. To this end, there has been great interest in finding renewable and environmentally friendly materials to promote environmental sustainability and combat harmful pollutants in wastewater. Of the many options, lignocellulose, as an abundant, biocompatible and renewable material, is the most attractive candidate for water remediation due to the unique physical and chemical properties of its constituents. Herein, we review the latest research advances in lignocellulose-based adsorbents, focusing on lignocellulosic composition, material modification, application of adsorbents. The modification and preparation methods of lignin, cellulose and hemicellulose and their applications in the treatment of diverse contaminated water are systematically and comprehensively presented. Also, the detailed description of the adsorption model, the adsorption mechanism and the adsorbent regeneration technique provides an excellent reference for understanding the underlying adsorption mechanism and the adsorbent recycling. Finally, the challenges and limitations of lignocellulosic adsorbents are evaluated from a practical application perspective, and future developments in the related field are discussed. In summary, this review offers rational insights to develop lignocellulose-based environmentally-friendly reactive materials for the removal of hazardous aquatic contaminants.