Removal of Cd2+, Zn2+, and Sr2+ by Ion Flotation, Using a Surface-Active Derivative of DTPA (C12-DTPA)

Enhancing Zn (II) recovery efficiency: Bi-divalent nickel-cobalt ferrite spinel NiXCo1-xFe2O4 as a Game-changing Adsorbent-an experimental and computational study

This study presents a comprehensive investigation into NiXCo1-xFe2O4 (x = 0.5) spinel nanoparticles synthesized through a one-pot hydrothermal method using Co(NO3)2.6H2O and Ni(NO3)2.6H2O salts. XRD, FTIR, FESEM, and VSM analyses confirmed a cubic structure of NiXCo1-xFe2O4 (x = 0.5) nanoparticles without impurities. These nanoparticles exhibit efficient Zn (II) adsorption characteristics, following Langmuir isotherm and pseudo-second-order kinetics. The maximum adsorption capacity was measured to be 666.67 mg g-1 at pH = 7, with mechanisms involving both electrostatic attraction and cation exchange. Desorption studies indicate more than 75% Zn (II) recovery in an acidic environment (pH = 2) after three cycles. Computational analysis was used to validate the experimental results through Molecular Dynamics simulations, initially focusing on NiXCo1-xFe2O4 (x = 0.5). Further exploration involved variations in x at 0.25 and 0.75 to identify the optimal Ni and Co ratio in this bivalent cation spinel ferrite. Computational analyses reveal the superior performance of NiXCo1-xFe2O4 (x = 0.75) in Zn (II) removal, supported by radial distribution analysis, VdW energy, Coulombic energy, mean square displacement (MSD), root mean square displacement (RMSD), and interaction energy. This comprehensive study provides valuable insights into the adsorption behavior and structural stability of NiXCo1-xFe2O4 nanoparticles, showcasing potential applications in Zn (II) removal.

Application and development of foam extraction technology in wastewater treatment: A review

With the advancement of technology, wastewater treatment has become a significant challenge limiting the clean and sustainable development of chemical and metallurgical industries. Foam extraction, based on interfacial separation and mineral flotation, has garnered considerable attention as a wastewater treatment technology due to its unique physicochemical properties. Although considerable excellent accomplishments were reported, there still lacks a comprehensive summary of process features and contaminant removal mechanisms via foam extraction. According to the latest research progresses, the principles and characteristics of foam extraction technology, the classification and application of flotation reagents are systematically summarized in this work. Then comprehensively commented on the application fields and prospects of iterative flotation technology such as ion flotation, adsorption flotation and floating-extraction. The shortcomings and limitations of the current foam extraction technologies were discussed, and the feasible process intensification techniques were highlighted. This review aims to enchance the understanding of the foam extraction mechanism, and provides guidance for the selection appropriate reagents and foam extraction technologies in wastewater treatment.

Aminopoly(carboxylic acid)-Functionalized PolyHIPE Beads toward Eliminating Trace Heavy Metal Ions from Water

Many advanced materials are designed for the removal of heavy metal ions from water. However, materials for eliminating trace heavy metal ions from wastewater to meet drinking water standards remain a major challenge. Herein, epoxy group-functionalized open-cellular beads are synthesized by UV polymerization of a water-in-oil-in-water system. The epoxy groups are further transformed into diethylenetriaminepentaacetic acid (DTPA) with hexamethylene diamine as a bridging agent. The resulting material (DTPA@polyHIPE beads) can eliminate trace Cu(II), Cr(III), Pb(II), Fe(III), or Cd(II) from water. When 0.15 g of DTPA@polyHIPE beads are used to adsorb metal ions of 20 mg in 100 mL of water, the residue concentrations of Cu(II), Cr(III), Pb(II), Fe(III), and Cd(II) are reduced to 0.08, 0.06, 0.02, 0.09, and 0.07 mg/L, respectively. The adsorption efficiencies of the beads for these ions are all higher than 99.55%. The adsorbent is durable and exhibits good recyclability by retaining an adsorption capacity of ≥91% after 5 cycles. The negative values of ΔG in the adsorption process indicate that the adsorption is feasible and spontaneous. The chemical adsorption follows the Freundlich adsorption model, indicating a multilayer heterogeneous adsorption. The DTPA@polyHIPE beads have a great potential application in dealing with trace heavy metal ion polluted water.

Liquid foams: Properties, structures, prevailing phenomena and their applications in chemical/biochemical processes

Liquid foams are gas-liquid dispersions with flexible structures that provide high gas-liquid interfaces. This property nominates liquid foams as excellent gas-liquid contactors, systems that are widely used in the chemical and biochemical industries. However, challenges such as a lack of comprehensive understanding and foam instability have historically hindered their widespread industrial use in most applications. It was not until the recent development of nanofluidics, nanotechnology, surface science, and other related fields that the understanding, analysis, and control of foam phenomena improved. This led to the development of innovative stabilization techniques and foam-based unit operations in chemical and biochemical processes, each of which requires in-depth and exclusive reviews to fully comprehend their potential and limitations and to identify areas for further improvement and innovation. This paper reviews the foams, the common phenomena in them, the characteristics that make them suitable for chemical/biochemical engineering, reports on their current applications and recent developments in this field.

Removal of hazardous ions from aqueous solutions: Current methods, with a focus on green ion flotation

Hazardous ions, like those of heavy metals, cause significant health and environmental problems when they are discharged into water resources naturally or through various industrial processes. Removing these ions from water is of significant importance in the provision of high-quality water for drinking and agricultural usage. This work discusses current techniques that are frequently used for the removal of heavy-metal ions from aqueous solutions by absorption, particularly the use of biodegradable surfactants in ion flotation. Certain new surfactants promise high efficiency in their use in the ion-flotation process and in their application in industrial-water treatment to remove heavy metals. As an example, this work demonstrates the high efficiency of surfactants based on an amino-acid (L-cysteine) in removing a range of heavy-metal ions in a simple, single-stage ion-flotation process. High foaming ability, the ability to operate in various temperatures and pHs, decomposing into natural products and high binding affinity for heavy-metal ions make the cysteine-based surfactants a highly suitable compound to replace current commercial surfactants in ion- and froth-flotation processes. Removal of particular ions can also be achieved in ion flotation; a suitable choice of parameters, such as pH and surfactant concentration, favours the surfactant binding to those ions. Further intensive work is required to develop an optimal process to recover valuable elements from waste solutions.

Recovery of copper, zinc and lead from photovoltaic panel residue

The increase in photovoltaic panel installations in Europe will generate vast amounts of waste in the near future. Therefore, it is important to develop new technologies that allow the recycling of end-of-life photovoltaic panels. This material can serve as a secondary resource, not only for precious metals (e.g. silver), but also for base metals. In this work, the extraction and recovery of the base metals copper, zinc and lead from a copper-rich photovoltaic panel residue was investigated. The material was first leached at 80 °C under microwave irradiation with a mixture of hydrochloric acid, sodium chloride and hydrogen peroxide solutions. Based on the Box-Behnken factorial design optimization, it was possible to extract 81.2% of Cu, 96.4% of Zn and 77.6% of Pb, under the following leaching conditions: [HCl] = 0.5 mol L^-1, [NaCl] = 200 g L^-1, [H₂O₂] = 7.5 wt% and t = 60 min. Cementation with iron powder at a 1.2 iron-to-copper stoichiometric ratio allowed the recovery of copper nearly quantitatively (99.8%) as a copper-iron sediment. The gas-liquid separation technique of ion flotation was employed to separate lead and zinc from the dilute copper-free leachate. Cetyltrimethylammonium bromide (CTAB), a cationic surfactant, selectively recovered lead (99.4%) over zinc as lead(ii) tetrachloro cetyltrimethylammonium colloid, after eight ion flotation stages and [CTAB]_total = 7.2 mmol L^-1. The zinc that remained in the solution after the ion flotation step was recovered by precipitation and by adding sodium sulfide at 110% of the stoichiometric amount after removing iron as ferric hydroxide by slowly raising the pH to 3.7.

Synthesis, characterization, and assessment of novel sulfonated polynorbornene dicarboximides as adsorbents for the removal of heavy metals from water

The occurrence of heavy metals in the natural aquatic systems arising from anthropogenic sources is an issue of global and environmental concern because of their extremely harmful effects to living beings even in rather low concentrations. The synthesis and ring-opening metathesis polymerization (ROMP) of novel norbornene dicarboximides bearing highly aromatic pendant groups, specifically, N-4-tritylphenyl-norbornene-5,6-dicarboximide (2a) and N-2,4,6-(triphenyl)phenyl-norbornene-5,6-dicarboximide (2b), their hydrogenation and further polymer sulfonation to render them adsorbents for the uptake of heavy metal ions from water is reported in this study. The macromolecules were characterized by means of FT-IR, ¹H NMR, and thermal analysis, among others. A thoroughly kinetic and isothermal study of adsorption in single and ternary aqueous solutions of Pb²⁺, Cd²⁺, and Ni²⁺ was performed considering several experimental variables for instance initial metal concentration, contact time and solution pH. In general, the experimental data were adjusted more efficiently to the pseudo-second order kinetic model and to the Freundlich isotherm model, respectively. The maximum removal amounts were found to be 55.7 mg/g for Pb²⁺, 33.9 mg/g for Cd²⁺, and 10.2 mg/g for Ni²⁺ in the sulfonated trityl-bearing polymer 5a while those found for the sulfonated triphenyl-bearing polymer 5b were 31.5 mg/g for Pb²⁺, 26.6 mg/g for Cd²⁺, and 7.0 mg/g for Ni²⁺, respectively. The higher heavy metal removal capacity of polymer 5a was attributed to its also higher degree of sulfonation. The outcomes indicate that these novel sulfonic acid containing polymer-based adsorbents are effective for the uptake of heavy metallic elements from water.

Heavy Metals Removal from Water by Efficient Adsorbents

Natural occurrence and anthropogenic practices contribute to the release of pollutants, specifically heavy metals, in water over the years. Therefore, this leads to a demand of proper water treatment to minimize the harmful effects of the toxic heavy metals in water, so that a supply of clean water can be distributed into the environment or household. This review highlights several water treatment methods that can be used in removing heavy metal from water. Among various treatment methods, the adsorption process is considered as one of the highly effective treatments of heavy metals and the functionalization of adsorbents can fully enhance the adsorption process. Therefore, four classes of adsorbent sources are highlighted: polymeric, natural mineral, industrial by-product, and carbon nanomaterial adsorbent. The major purpose of this review is to gather up-to-date information on research and development on various adsorbents in the treatment of heavy metal from water by emphasizing the adsorption capability, effect of pH, isotherm and kinetic model, removal efficiency and the contact of time of every adsorbent.

Coffee Grounds-Derived CNPs for Efficient Cr(VI) Water Remediation

Carbon nanomaterials are a group of materials characterized by sp2/sp3 carbon backbone which, combined with surface atoms and/or chemical groups, ensures peculiar physical chemical features for a wide range of applications. Among these materials, carbon dots and carbon nanoparticles belong to carbon nanomaterials with a few nanometer dimensions. In this work, carbon nanoparticles were produced from spent coffee grounds as sustainable carbon source through a simple, cheap and eco-friendly procedure according to an oxidation process (at controlled temperature) driven by hydrogen peroxide. Atomic Force Microscope (AFM) and fluorescence, UV-Vis absorption, FT-IR and Raman spectroscopy were used to assess the formation of carbon nanomaterials of about 10 nm with the typical emission and absorption properties of carbon dots and peculiar surface features. In fact, the presence of heteroatoms, i.e., phosphorus, and the carbonyl/carboxyl surface groups on carbon nanoparticles, was proposed to confer peculiar properties allowing the fast Mn(VII) reduction to Mn(II) at neutral pH and the Cr(VI) reduction to Cr(III) in weak acid aqueous media.

Comprehensive evaluation on a prospective precipitation-flotation process for metal-ions removal from wastewater simulants

Toxic metal pollutants threaten water environment. It exists undesirably metal-ion concentration limits with conventional precipitation flotation. An enhanced precipitation flotation system focusing on efficient removal for bivalent metal-ions was researched. The system involved the addition of humics and Fe³⁺ to generate and regulate the precipitates. The characteristics of precipitates were investigated by particle analysis, conditional stability constants and DLVO theory calculations, and SEM&TEM imaging. The results reveal that metal-ions chelate with humics at low metal-ion concentration, with generating the limited micro-size precipitates of <2.0 μm, fractal dimension of 1.60-1.80 and precipitate efficiency of <91.00%. By adding trivalent Fe³⁺, the macro-size precipitates are obtained with particle size of approximate 10.0 μm, fractal dimension of 1.50-1.60, and nearly-total flotation removal of precipitate. The chelating interaction of Fe³⁺ with humics is the mainly regulating mechanism, which could enhance the conditional stability constants and the precipitate efficiency of metal-ions at low concentration. The desired precipitate particles are finally obtained by breaking the limitations of metal-ion concentration. Finally, the flotation removal of metal-ions from single or mixed solutions is respectively 99.10 ± 0.10% for Cu²⁺, 99.60 ± 0.10% for Pb²⁺, and 94.30 ± 0.30% for Zn²⁺. Therefore, the enhanced precipitation flotation process is an efficient purification approach for metal-containing wastewaters.

A review of the applications of ion floatation: wastewater treatment, mineral beneficiation and hydrometallurgy

The applications, progress and outlook of ion flotation are discussed.

Selective separation of heavy metal ions from dilute aqueous solutions by foams and micelles of surfactants

Traditional metal ion separation by surfactant foams is dependent on the interaction difference of various metal ions with surfactant monomers rather than surfactant aggregates, because the binding of metal ions with surfactant aggregates retains the metal ions in bulk solution. This kind of separation method is only effective for the metal ions with obvious differences in valence, size or coordination ability. The present study proposes a novel separation method based on the binding affinity difference of metal ions with micelles and monomers of two surfactants to selectively separate multivalent ions Cr3+, Ni2+ and Cu2+ from their dilute mixed aqueous solution. The two surfactants are single-chain surfactant sodium dodecyl sulfate (SDS) and gemini surfactant 1,3-bis(N-dodecyl-N-propanesulfonate sodium)-propane (C12C3C12(SO3)2), which show negligible synergism because they are both negatively charged and hold a significantly different self-assembling ability, thus allowing the coexistence of SDS/C12C3C12(SO3)2 micelles with SDS monomers. At first, Cr3+ ions were separated from Cu2+ and Ni2+ ions by the foam generated by the SDS monomers due to more intensive electrostatic interaction of Cr3+ ions with the SDS monomers. Afterwards Ni2+ ions were separated from Cu2+ ions by utilizing the high binding affinity of Cu2+ with the SDS/C12C3C12(SO3)2 micelles in the bulk solution and Ni2+ with the SDS monomers in the foam. This work has proved that micelles can assist the selective separation of "twin-like" metal ions Ni2+ and Cu2+ when the concentrations of monomers and micelles are properly adjusted.

Nonionic Glycolipids for Chromium Flotation- and Emulsion (W/O and O/W)-Based Bioactive Release

Biosourced surfactants are endeavored as a green alternative to biosurfactants and petrochemical surfactants having industrial utilization. Nine glycolipids with headgroup and chain length variation were derived from renewable resources like vegetable oils, carbohydrates, and amino acids. The concentration-dependent interfacial activity, foamability, wetting power, emulsification power, and solubilization capacities of glycolipids were investigated to provide a structure-activity relationship. Later, the metal flotation and emulsification experiments were performed. In general, for metal flotation, the surfactant should contain a hydrophobic tail, hydrophilic head, and chelating function. In the present investigation, it was observed that the headgroup of a glycolipid can serve as a hydrophilic head as well as perform a chelating function. Moreover, heat energy generated from the sunlight was utilized for metal flotation. Additionally, these glycolipids are capable to form stable sunflower oil-water (W/O and O/W) emulsions. The mechanical and thermal stabilities and hydrophobic chain length dependency of the prepared emulsions at different water volume fractions are explored. Furthermore, encapsulation and release of water-soluble (riboflavin and l-ascorbic acid) and oil-soluble (curcumin and α-tocopherol) bioactives in glycolipid emulsions were monitored. Thus, glycolipids under investigation had shown the possibility for pretreatment of chromium-containing wastewaters and bioactive-loaded emulsions toward the controlled release.