Removal of phosphate and aluminum from water in single and binary systems using iron-modified carbons

Sustainable utilization of Fe3O4-modified activated lignite for aqueous phosphate removal and ANN modeling

Lignites are widely available and cost-effective in many countries. Sustainable methods for their utilization drive innovation, potentially advancing environmental sustainability and resource efficiency. In the present study, Fe3O4 (∼25.1 nm) supported on KOH-activated lignite (A-L) displayed 8 times higher phosphate removal than pristine A-L (67.6 mg/g vs. 8.5 mg/g at pH 5, 50 mg of absorbent in 25 mL of 1500 ppm [phosphate]), owing to its abundant Fe3O4 (10 wt% of Fe) nanoparticle content. The removal occurred within ∼2 h, following a pseudo-second-order kinetic model. Across pH levels ranging from 5.0 to 9.0, Fe3O4-A-L's phosphate removal occurs via both chemisorption and precipitation, as evident by kinetic, pH, and XPS analyses. The phosphate adsorption fits better with the Freundlich isotherm. The combined benefits of facile recovery, rapid phosphate uptake, straightforward regeneration, and attractive post-adsorption benefits (e.g., possibly use as a Fe, P-rich fertilizer) make magnetic Fe3O4-A-L a promising candidate for real-world applications. Artificial Neural Network (ANN) modeling indicates an excellent accuracy (R2 = 0.99) in predicting the amount of phosphate removed by Fe3O4-A-L. Sensitivity analysis revealed both temperature and initial concentration as the most influencing factors. Leveraging lignite in environmentally friendly applications not only addresses immediate challenges but also aligns with sustainability goals. The study clearly articulates the potential benefits of utilizing lignite for sustainable phosphate removal and recovery, offering avenues for mitigating environmental concerns while utilizing resources efficiently.

Preparation of chitosan mesoporous membrane/halloysite composite for efficiently selective adsorption of Al(III) from rare earth ions solution through constructing pore structure on substrate

The removal of impurity Al(III) from rare earth ion solution by selective adsorption method was one of the challenging tasks. Herein, calcination and acid dissolution treatment were used to construct the pore structure for the halloysite substrate (Hal-650-H) and provide conditions for the formation of the chitosan mesoporous membrane to prepare composite (Hal-H-2CS). The selective adsorption properties and mechanism of the Hal-H-2CS for Al(III) in the rare earth ion solution were studied. The results showed that the formation of mesoporous structures for chitosan provided abundant sites for the adsorption of Al(III). Hal-H-2CS showed remarkable selective adsorption properties for Al(III) in a wide pH range and the binary mixtures with high content of Al(III) or La(III). The maximum adsorption capacity of Al(III) was 106 mg/g, while the adsorption capacity of La(III) was only 1.41 mg/g at pH 4.0. In addition, the Hal-H-2CS exhibited excellent regeneration and structural stability. The remarkable selective properties of Hal-H-2CS was achieved by the synergistic effect between chitosan mesoporous membrane and Hal-650-H, the main adsorption sites were the OH, NH2, CONH2 of chitosan and the oxygen sites of the Hal-650-H. This work provides a new strategy for the design and preparation of outstanding selective adsorbent for Al(III).

Functionalization of Silica Nanoparticles by 5-Chloro-8-quinolinol as a New Nanocomposite for the Efficient Removal and Preconcentration of Al3+ Ions from Water Samples

In this work, silica nanoparticles were modified by 5-chloro-8-quinolinol as a new nanocomposite for the efficient elimination and preconcentration of Al³⁺ ions from several water sources. The fabricated composite was characterized utilizing XRD, SEM, FT-IR, TEM, CHN elemental analyzer, and N₂ adsorption/desorption analyzer. The XRD demonstrated the existence of a wide peak at 2θ = 30°. Also, all the peaks of silica were severely reduced, which confirms the success of loading the 5-chloro-8-quinolinol on the surface of the silica. The SEM and TEM images demonstrated that the composite resembled cotton, and this confirms that 5-chloro-8-quinolinol was successfully loaded on the silica surface. The specific surface area, the average pore size, and the total pore volume of the synthesized composite are 80.53 m²/g, 3.26 nm, and 0.185 cc/g, respectively. In addition, the greatest uptake capacity of the synthesized composite toward aluminum ions is 95.06 mg/g. The results indicated that the adsorption of aluminum ions onto the silica/5-chloro-8-quinolinol composite follows the Langmuir isotherm and pseudo-second-order model. Moreover, the adsorption of aluminum ions by the silica/5-chloro-8-quinolinol composite is spontaneous, chemical, and thermodynamically favorable. The values of % recovery were more than 97%, whereas the values of % RSD were less than 3.5%. Hence, this confirms the effectiveness of the proposed method in the determination of aluminum ions in real water samples.

Identifying Geogenic and Anthropogenic Aluminum Pollution on Different Spatial Distributions and Removal of Natural Waters and Soil in Çanakkale, Turkey

The Çanakkale-Kirazlı region (Turkey) is enriched with minerals, especially aluminum (Al), which dangerously get transported into aquatic media due to several mining and geological activities in recent years. In this study, Al and other potentially toxic metals (PTMs) including B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, and Zn, in both water and soil samples, were measured for quality determination. Selected metals were also analyzed by the enrichment factor (EF), the geoaccumulation index (I _geo), the contamination factor (CF), and the pollution load index (PLI) to evaluate both water and soil pollution geogenically or anthropogenically. Also, the metals were clustered to support the pollution source with Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Forty-five natural water samples and 12 soil samples were collected spatially. To perform pollution assessment, two fundamental treatment processes to remove Al pollution from the sample including the highest Al concentration (38.38 mg/L) in water were applied: (1) precipitation with pH adjustment and (2) removal with ion exchange. The pH values of water samples were changed in the range of 3-9 to test the dissolution of Al. The results demonstrated that the study area was mostly under the influence of geogenic aluminum pollution.

Immobilized Nanomaterials for Environmental Applications

Nanomaterials (NMs) have been extensively used in several environmental applications; however, their widespread dissemination at full scale is hindered by difficulties keeping them active in engineered systems. Thus, several strategies to immobilize NMs for their environmental utilization have been established and are described in the present review, emphasizing their role in the production of renewable energies, the removal of priority pollutants, as well as greenhouse gases, from industrial streams, by both biological and physicochemical processes. The challenges to optimize the application of immobilized NMs and the relevant research topics to consider in future research are also presented to encourage the scientific community to respond to current needs.

Phosphate Removal from Wastewater by Magnetic Amorphous Lanthanum Silicate Alginate Hydrogel Beads

It is of both fundamental and practical importance to develop effective adsorbents for removing phosphate from aqueous solutions continuously. In this study, magnetic amorphous lanthanum silicate alginate hydrogel beads (MALS-B) were prepared and used for phosphate removal. Mesoporous silica materials with highly ordered and hexagonal channel structures were synthesized from natural mineral rectorite (REC) at room temperature. On this basis, amorphous lanthanum silicate (ALS) was synthesized by theone-pot method using a silicon source from REC and a commercial lanthanum source. Further, MALS-B were synthesized from sodium alginate (SA) with ALS and Fe3O4 as the incorporated adsorbable and magnetic nanoparticles via a simple cross-linking method in CaCl2 solution. The synthesized hydrogel beads were characterized by various techniques. ALS and Fe3O4 existed relatively independently in MALS-B, where ALS provided adsorption sites and Fe3O4 provided magnetism. They played a synergistic role in phosphate removal. The saturation magnetization value of MALS-B was 17.38 emu/g, enabling theirfacile separation from aqueous solutions after phosphate adsorption. MALS-B exhibited a preferable adsorption capacity of 40.14 mg P/g for phosphorus compared to other hydrogel beads based on adsorption experiments. More significantly, MALS-B exhibited excellent selectivity for phosphate in aqueous solutions with various interfering ions and possessed a high affinity to phosphate in a wide pH range. MALS-B showed the treatment volume of 480 BV when effluent phosphate concentration was below 0.5 mg/L in fixed-bed column adsorption. The adsorption mechanism was also revealed. Our work demonstrates that MALS-B can serve as a promising adsorbent for continuous phosphate adsorption.

Carbonaceous materials for removal and recovery of phosphate species: Limitations, successes and future improvement

The carbonaceous materials have gained significant interest for the phosphorus species remediation and recovery in the last decade. Carbonaceous materials present many unique features, such as cost effective, availability, environmentally friendly, and high removal efficiency that make them a promising adsorbent. In this review, the recent application of carbonaceous materials including activated carbon (AC), graphene and graphene oxide (GO), lignin, carbon nanotubes (CNTs), and gC₃N₄ for phosphate removal and recovery were comprehensively summarized. The kinetics and isotherm models, removal mechanisms, and effects of operating parameters are reported. The reusability, lifetime of carbonaceous materials, and impact of modification were also considered. The modified carbonaceous materials have significantly high phosphate adsorption capacity compared to unmodified adsorbents. Namely, MgO-functionalized lignin-based bio-charcoal exhibited a 906.8 mg g^-1 of capacity as the highest one among other reviewed materials. The modification of carbonaceous materials with various elements has been presented to improve the surface functional groups, surface area and charge, and pore volume and size. Among these loaded elements, iron has been effectively used to provide a prospect for magnetic recovery of the adsorbent as well as increase phosphate adsorption. Furthermore, the phosphate recovery methods, phosphate removal efficiency of carbonaceous materials, the limitations, important gaps in the literature, and future studies to enhance applicability of carbonaceous materials in real scale are also discussed.