A Comparison of Palladium Sorption Using Polyethylenimine Impregnated Alginate-Based and Carrageenan-Based Algal Beads

Modified alginate materials for wastewater treatment: Application prospects

Sodium alginate is a natural macromolecule widely used because of its abundance, low cost of acquisition, and rich hydroxyl and carboxyl groups in the matrix. The physical modification of sodium alginate can be made by blending it with polymer materials. The so-yielded alginate complex is commonly unstable in an aqueous environment due to alginate backbones' high hydrophilicity. The chemical modification can remove its hydrophilic groups and introduce special functional groups or polymers onto the alginate backbones to provide excess reaction sites for specific reactions and effective complexation sites for accommodating antibiotics, dyes, heavy metal ions, and radioactive elements. Sodium alginate has been used in water treatment engineering under revised modification protocols. This article also reviews the latest modification protocols for sodium alginate and outlines the novel application of the modified materials. The limitations of modified sodium alginate materials are described, and research prospects are put forward.

Functionalization of melamine sponge for the efficient recovery of Pt(IV) from acid leachates

The recovery of platinum from industrial waste is of critical importance. Usually, the recovery method is to dissolve the solid waste with acid to form a solution where platinum mainly exists in the form of Pt(IV). Therefore, it is urgent to efficiently and selectively adsorb Pt(IV) ions from acid leachates. In this study, a highly efficient adsorbent was developed by grafting of carboxyl and amine groups onto melamine sponge with alginate-Ca and polyethylenimine-glutaraldehyde (ML/ACPG). Combination of SEM, FTIR and XPS showed that the ML/ACPG sponge had a tree structure and the amino, carboxyl and hydroxyl groups were successfully introduced. Maximum adsorption capacity of ML/ACPG sponge reached up to 101.1 mg/L at pH of 1 (optimum initial pH value). The Pt(IV) ions were readily desorbed (within 60-80 min) using 0.1 M HCl + 0.025 M thiourea solution. Desorption efficiency remained higher than 83.3% while adsorption capacity decreased by less than 6.0% after 5 cycles operation. The ML/ACPG sponge was stable in 3 M of HNO3, NaCl after shaking for 72 h at 300 rpm with mass loss less than 2.5%. The mechanism of Pt(IV) adsorption onto ML/ACPG sponge mainly involved coordination by electrostatic attraction and carboxyl groups by protonated amine groups. The above results confirmed that the ML/ACPG sponge has a good practical application potential for Pt(IV) recovery from acid leachates.

A review on algal biosorbents for heavy metal remediation with different adsorption isotherm models

Biosorbent composites like chitin, alginate, moss, xanthene, and cotton can be derived from biotic species such as plants, algae, fungi, and bacteria which can be used for the exclusion of both organic and inorganic toxicants from sewage, industrial effluent, polluted soils, and many more. The use of composites in place of raw substrates like alginate and chitin increases the adsorption capacity as CS₄CPL₁ beads increase the adsorption capacity for copper and nickel from 66.7 mg/g and 15.3 mg/g in the case of alginate microsphere to 719.38 mg/g and 466.07 mg/g respectively. Biosorbent fabricated from algae Chlorella vulgaris having surface area of 12.1 m²/g and pore size of 13.7 nm owing to which it displayed a higher adsorption capacity for Pb 0.433 mmol/g indicating their potential as an efficient biosorbent material. This article contains detailed information related to heavy metals as well as biosorbent that includes different isotherms, kinetics, techniques to estimate heavy metal concentration, removal methods, and adverse health effects caused due to heavy metal pollution. Apart from the above recovery and reuse of biosorbent, correlation with the sustainable development goals has also been included.

Recent developments in hydrogels containing copper and palladium for the catalytic reduction/degradation of organic pollutants

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants. Accordingly, the elimination of inorganic and organic pollutants using sustainable, effective, and low-cost heterogeneous catalysts is considered as one of the most essential routes for this aim. Thus, many efforts have been devoted to the synthesis of novel compounds and improving their catalytic performance. Recently, palladium- and copper-based hydrogels have been used as catalysts for reduction, degradation, and decomposition reactions because they have significant features such as high mechanical strength, thermal stability, and high surface area. Herein, we summarize the progress achieved in this field, including the various methods for the synthesis of copper- and palladium-based hydrogel catalysts and their applications for environmental remediation. Moreover, palladium- and copper-based hydrogel catalysts, which have certain advantages, including high catalytic ability, reusability, easy work-up, and simple synthesis, are proposed as a new group of effective catalysts.

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants.

In Situ Functionalization of Iron Oxide Particles with Alginate: A Promising Biosorbent for Retention of Metal Ions

In this study, alginate extracted from marine algae biomass was used for the functionalization of iron oxide particles obtained in situ. This procedure ensured a complete recovery of the alginate from the aqueous solution obtained after extraction and allowed the preparation of a new biosorbent. The obtained iron oxide microparticles functionalized with alginate (Alg-Fe₃O₄-MPs) were analyzed (FTIR spectrometry, energy dispersive X-ray spectroscopy and scanning electron microscopy), and their biosorptive performance was tested for the removal of Cu(II), Co(II) and Zn(II) ions. The optimal conditions were established as pH = 5.4, adsorbent dosage of 2 g/L, contact time of minimum 60 min and room temperature (23 ± 1 °C). The retention of metal ions was quantitative (99% for Cu(II), 89% for Co(II) and 95% for Zn(II)) when the concentration of metal ions was less than 0.80 mmol M(II)/L. The Langmuir model was found to be the best fitted model for the equilibrium data, while biosorption kinetics followed the pseudo-second order model. Biosorption processes were spontaneous (ΔG⁰ < 0), endothermic (ΔH⁰ > 0), and accompanied by an increase in entropy (ΔS⁰ > 0). The high maximum biosorption capacity of Alg-Fe₃O₄-MPs and its good regeneration highlight the potential of this biosorbent for applications in decontamination processes.

Efficacy of treated sodium alginate and activated carbon fibre for Pb(II) adsorption

Efficacy of treated sodium alginate (TSA) and activated carbon fibre (ACF) for aqueous Pb(II) uptake was comparatively investigated. By employing FTIR, SEM, EDX, XRD, point of zero charges and surface area measurements, the available functional groups, morphology, crystallinity, surface charge and surface areas of both adsorbents were respectively elucidated. The Pb(II) uptake performance of both adsorbents was also studied via batch mode at varied process conditions. The experimental isotherm and kinetic data for both adsorbents were best fitted to nonlinear forms of Langmuir and pseudo-first-order models, respectively. Similarly, intraparticle diffusion was the sole controlling mechanism. Despite the huge variation in the surface area, TSA (7.8 m²/g) with high carboxyl content (395.6 meq-COOH/100 g of sample) performed better by all standards than the ACF (975 m²/g). This finding showed that although the surface area of a given adsorbent is a key indicator of its adsorptive performance, the inherent surface functional groups play a superior role. The experimentally derived maximum adsorption capacities of 221.25 mg/g (for TSA) and 183.34 mg/g (for ACF) were recorded at an equilibrium time of 30 min and 45 min, respectively. Therefore, TSA and ACF demonstrated effectiveness for aqueous Pb (II) sequestration.

Quaternization of Composite Algal/PEI Beads for Enhanced Uranium Sorption-Application to Ore Acidic Leachate

The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with glycidyltrimethylammonium chloride). The sorbent is fully characterized by FTIR, XPS for confirming the contribution of protonated amine and quaternary ammonium groups on U(VI) binding (with possible contribution of hydroxyl and carboxyl groups, depending on the pH). The sorption properties are investigated in batch with reference to pH effect (optimum value: pH 4), uptake kinetics (equilibrium: 40 min) and sorption isotherms (maximum sorption capacity: 0.86 mmol U g-1). Metal desorption (with 0.5 M NaCl/0.5 M HCl) is highly efficient and the sorbent can be reused for five cycles with limited decrease in performance. The sorbent is successfully applied to the selective recovery of U(VI) from acidic leachate of uranium ore, after pre-treatment (cementation of copper, precipitation of rare earth elements with oxalate, and precipitation of iron). A pure yellow cake is obtained after precipitation of the eluate.