Single step modification of micrometer-sized polystyrene particles by electromagnetic polyaniline and sorption of chromium(VI) metal ions from water

Capturing Acidic CO2 Using Surface-Active Difunctional Core-Shell Composite Polymer Particles via an Aqueous Medium

Multifunctional surface-active polymeric composites are attractive materials for the adsorption of various small molecules. Herein, dual-functionalized micron-sized surface-active composite polymer particles were prepared by a three-step process for CO2 adsorption. First, polystyrene (PS) seed particles were prepared via the dispersion polymerization of styrene. PS/P(MMA-AAm-EGDMA) composite polymer particles were then synthesized by aqueous seeded copolymerization of methyl methacrylate (MMA) and acrylamide (AAm) in the presence of an ethylene glycol dimethacrylate (EGDMA) cross-linker. Finally, the amide moieties of PS/P(MMA-AAm-EGDMA) composite particles were converted into an amine-functionalized composite by using the Hofmann degradation reaction. The presence of primary amine groups on the surface of aminated composite particles was confirmed by some conventional chemical routes, such as diazotization and Schiff's base formation reactions. The formation and functionality of the PS seed, PS/P(MMA-AAm-EGDMA), and aminated PS/P(MMA-AAm-EGDMA) composite polymer particles were confirmed by Fourier transform infrared (FTIR) spectra analyses. Scanning electron microscopy (SEM) analysis revealed spherical shape, size, and surface morphologies of the PS seed, reference composite, and aminated composites. The elemental surface compositions, surface porosity, pore volume, pore diameter, and surface area of both composite particles were evaluated by energy-dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses. Dynamic light scattering (DLS) and ζ-potential measurements confirmed the pH-dependent surface properties of the functionalized particles. The amount of the adsorbed anionic emulsifier, sodium dodecyl sulfate (SDS), on the surface of aminated PS/P(MMA-AAm-EGDMA) is higher at pH 4 than that at pH 10. A vice versa result was found in the case of cationic surfactant, hexadecyltrimethylammonium bromide (HTABr), adsorption. Synthesized aminated composite particles were used as an adsorbent for CO2 adsorption via bubbling CO2 in an aqueous medium. The changes in dispersion pH were monitored continuously during the adsorption of CO2 under various conditions. The amount of CO2 adsorption by aminated composite particles was found to be 209 mg/g, which is almost double that of reference composite particles.

Algae extract delamination of molybdenum disulfide and surface modification with glycidyl methacrylate and polyaniline for the elimination of metal ions from wastewater

A special type of two-dimensional (2D) material based conducting polymer was constructed by green synthesis and in-situ polymerization techniques. The 2D Molybdenum Disulfide (MoS₂) were first synthesized with the combination of, ammonium tetrathiomolybdate dissolved in 20 mL algae extract under stirring. After stirring for about 2 h, and then finally sulfurization was initiated using sulfur powder in 20 mL of sulfuric solution and stirred for 8 h. The resulting black precipitates of MoS₂ were collected by centrifugation at 5000 rpm. Moreover, the prepared MoS₂ was functionalized with glycidyl methacrylate (GMA) and form the MoS₂@PGMA. Further, the MoS₂@PGMA is combined with polyaniline (PANI) to form conducting polymer grafted thin film nanosheets named MoS₂@PGMA/PANI with a thickness in micrometer size through grafting method. The prepared materials were characterized by SEM, FTIR, XRD, XPS and EDX techniques. To check the performance of materials the adsorption study was performed. Moreover, the adsorption study toward Cu²⁺ and Cd²⁺ showed a tremendous results and the maximum adsorption was 307.7 mg/g and 214.7 mg/g respectively. In addition, the pseudo-first and second order models as well as the adsorption isotherm were investigated using the Langmuir and Freundlich model. The results were best fitted with the pseudo-second order and Langmuir models. The regeneration study was also conducted and MoS₂@PGMA/PANI nanosheets can be easily recycled and restored after five successful recycling. The established methodology for preparing the 2D materials and conducting polymer based MoS₂@PGMA/PANI nanosheets is expected to be applicable for other multiple applications.

Advances in Sorptive Removal of Hexavalent Chromium (Cr(VI)) in Aqueous Solutions Using Polymeric Materials

Sorptive removal of hexavalent chromium (Cr(VI)) bears the advantages of simple operation and easy construction. Customized polymeric materials are the attracting adsorbents due to their selectivity, chemical and mechanical stabilities. The mostly investigated polymeric materials for removing Cr(VI) were reviewed in this work. Assembling of robust functional groups, reduction of self-aggregation, and enhancement of stability and mechanical strength, were the general strategies to improve the performance of polymeric adsorbents. The maximum adsorption capacities of these polymers toward Cr(VI) fitted by Langmuir isotherm model ranged from 3.2 to 1185 mg/g. Mechanisms of complexation, chelation, reduction, electrostatic attraction, anion exchange, and hydrogen bonding were involved in the Cr(VI) removal. Influence factors on Cr(VI) removal were itemized. Polymeric adsorbents performed much better in the strong acidic pH range (e.g., pH 2.0) and at higher initial Cr(VI) concentrations. The adsorption of Cr(VI) was an endothermic reaction, and higher reaction temperature favored more robust adsorption. Anions inhibited the removal of Cr(VI) through competitive adsorption, while that was barely affected by cations. Factors that affected the regeneration of these adsorbents were summarized. To realize the goal of industrial application and environmental protection, removal of the Cr(VI) accompanied by its detoxication through reduction is highly encouraged. Moreover, development of adsorbents with strong regeneration ability and low cost, which are robust for removing Cr(VI) at trace levels and a wider pH range, should also be an eternally immutable subject in the future. Work done will be helpful for developing more robust polymeric adsorbents and for promoting the treatment of Cr(VI)-containing wastewater.

Fabrication of lanthanum/chitosan co-modified bentonite and phosphorus removal mechanism from low-concentration landscape water

It is essential to solve the problem of phosphorus pollution in urban landscape water and reduce the degree of eutrophication. In this paper, lanthanum-modified bentonite (La-B) was prepared by high-temperature calcination and liquid-phase precipitation. Then La-B was modified with chitosan to prepare a low-cost environment-friendly functional material: lanthanum/chitosan co-modified bentonite (La-BC). It can reach the adsorption equilibrium within 30 min, and the maximum adsorption capacity is 15.5 mg/g (initial phosphate concentration 50 mg/L); when the target concentration is 2 mg/L, the removal rate can reach 98.5%. La-BC has a stronger anti-interference ability to common coexisting anions SO₄^2-, HCO₃^-, NO₃^- and Cl^- in the urban landscape water body. La-BC has excellent performance in weakly acidic to neutral water, and its pH applicable range has been improved, making it possible to apply in practical water. The fitting results show that the adsorption behavior conforms to the pseudo-second-order kinetic model and the Freundlich model. After 5 regenerations, the removal efficiency remained around 80%. In the actual water test results, the phosphate concentration can be controlled below 0.1 mg/L and the removal rate is above 75%. Due to its low cost and reusability, it has great potential in the practical application of phosphate removal from landscape water.

Phosphate removal from actual wastewater via La(OH)3-C3N4 adsorption: Performance, mechanisms and applicability

In this study, La(OH)₃ nanoparticles were immobilized on C₃N₄ to effectively restrict their aggregation and subsequently enhance the La utilization efficiency to promote phosphate adsorption. The prepared La(OH)₃-C₃N₄ nanocomposite was characterized by SEM, XRD, FTIR, XPS, BET and Zeta potential analysis. Batch and continuously-fed (fixed-bed column) experiments to assess the adsorption performance of La(OH)₃-C₃N₄ showed that the composite exhibits superior utilization efficiency, resulting to relatively quick adsorption with a short equilibrium time of 30 min. The theoretical maximum P adsorption capacity reached the 148.35 mg·g^-1, efficiency that remained unaffected by the anions and HA present. The adsorption mechanism showed stability in a wide pH range (4.0-11.0) and is considered effective even after extensive use (five-cycles). The dynamics of the adsorption capacity and the half-penetration time values were estimated by 'Thomas' and 'Yoon-Nelson' models showed that are better represented from the experimental values obtained from the fixed-bed column trial. The adsorption mechanisms were attributed to surface precipitation, electrostatic attraction, and inner-sphere complexation via ligand exchange. Furthermore, La(OH)₃-C₃N₄ demonstrated high efficiency in scavenging phosphate from both diluted and concentrated wastewater (natural pond and swine wastewater respectively). The above confirm that La(OH)₃-C₃N₄ is a promising composite material for phosphate management in aqueous environments.

Smart Synthesis of Hollow Microporous Organic Capsules with a Polyaniline Modified Shell

In this work, novel hypercrosslinked polymer-based hollow microporous organic capsules with a polyaniline (PANI)-modified shell (PANI@S-HMOCs) are prepared by in-situ polymerization of aniline in the porous structure of the sulfonated hollow microporous organic capsules (S-HMOCs). PANI@S-HMOC1, PANI@S-HMOC2, and PANI@S-HMOC3 are made by adjusting S-HMOCs and aniline weight ratios of 4:1 and 3:1, and 2:1, respectively. The characterizations of PANI@S-HMOCs demonstrate that electrostatic interaction between aniline and sulfonic acid groups plays an important role in encapsulating PANI in the pores of the shell. The content of PANI showed an evident effect on the porosity of PANI@S-HMOCs, and an appropriate polyaniline loading amount may increase the surface area. PANI@S-HMOC1 and PANI@S-HMOC2 have higher BET surface areas (529 and 503 m² g^-1 ) than S-HMOCs (424 m² g^-1 ), but PANI@S-HMOC3 has lower BET surface area (380 m² g^-1 ). Based on the structural and textural features, PANI@S-HMOC2 shows good adsorption performance for Cr(VI) from aqueous media (156 mg g^-1 , pH = 2, and 27 mg g^-1 , pH = 7).

Cr(VI) visualization via transmittance of electrorheological display medium with core/shell polystyrene/polyvinyltetrazole microspheres

In the course of time, significant amounts of heavy-ion pollutants have been dispersed into the environment. Rapid on-site detection of heavy metal ions is crucial to monitor their dispersion in the nascent stages. In this study, 2.2-μm-diameter polystyrene microspheres (PSM) were synthesized via emulsifier-free polymerization to coat polyacrylonitrile (PSM@PAN) and form core/shell-structured microspheres. Core/shell polystyrene/polyvinyltetrazole (PSM@PVT) microspheres were obtained after a cyano-to-tetrazole conversion reaction, loaded in an electrorheological device (ERD) display constructed using two indium tin oxide glasses with a spacer seal. The ERD loading dispersed the microsphere solution by scattering light through the ERD, resulting in a low transmittance in the absence of an alternating electric field (AEF). Particles in the fluid medium were polarized to induce negative and positive charges at each end of the particles under the AEF, and the resultant particle chains enhanced transmittance. The optimal frequency to generate the highest degree of particle chaining in the presence of an AEF is defined as its characteristic frequency (Fc), which also serves as an indicator to identify the shell materials. The Fc of PSM@PVT shifted from 350 kHz to 30 kHz after adsorbing Cr(VI) from the PVT coating. Transmittance of the ERD loading of PSM@PVT with Cr(VI) increased linearly with the concentration of Cr(VI). Approximately 40 ng mL^-1 of the limit of detection was calculated in the linear range of 10-540 ng mL^-1. The Fc of the PSM@PVT adsorbing the Cr(VI) was not influenced by Na(I), K(I), Ca(II), Mg(II), Fe(III), and Zn(II) coexisting in the ERD.

Removal and Separation of Heavy Metal Ions from Multicomponent Simulated Waters Using Silica/Polyethyleneimine Composite Microparticles

Composite solid surfaces with high content of functional groups (FGs) are useful materials in different types of applications requiring stimuli-responsive "hard/soft" architectures, their improved properties rising from the combination of organic-inorganic parts. Among different types of weak polyelectrolytes, poly(ethyleneimine) (PEI) is of great interest in the construction of composite systems with thin layer-by-layer (LbL) organic films due to the large number of amino groups per unit mass of polymer. Herein, the spherical silica microparticles were modified with linear (L) or branched (B) PEI chains using LbL deposition of a copper complex (PEIL-Cu²⁺ or PEIB-Cu²⁺) and poly(acrylic acid) (PAA), glutaraldehyde selective cross-linking, followed by copper and PAA extraction from the multilayer. The newly formed silica/(PEIL)₁₀ and silica/(PEIB)₁₀ composites were used in batch and column sorption/desorption experiments of four heavy metal ions (Cu²⁺, Ni²⁺, Co²⁺, and Cd²⁺). In noncompetitive conditions ([FG]/Σ[M²⁺] > 9), all heavy metal ions were retained on composites, demonstrating the potential application of the prepared functional microparticles in surface water treatment. However, in competitive conditions ([FG]/Σ[M²⁺] < 9), only Cu²⁺ is sorbed in high amount (∼2.5 mmol·g^-1 PEI) on composites, with simultaneous displacement of already sorbed ions, demonstrating the solid-phase extraction and chromatographic properties of the synthesized silica/(PEIL)_n and silica/(PEIB)_n composites.

Elaboration of novel polyaniline@Almond shell biocomposite for effective removal of hexavalent chromium ions and Orange G dye from aqueous solutions

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g^-1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Effective Adsorption of Hexavalent Chromium and Divalent Nickel Ions from Water through Polyaniline, Iron Oxide, and Their Composites

Water pollution caused by industrial wastes containing heavy metals and dyes is a major environmental problem. This study reports on the synthesis, characterization, and utilizations of Polyaniline (PANI) and its composites with Fe3O4 for the removal of hexavalent chromium Cr(VI) and divalent nickel Ni(II) ions from water. The adsorption data were fitted in Freudlich, Langmuir, Tempkin, Dubbanin–Ruddishkawich (D–R), and Elovich adsorption isotherms. The Freundlich isotherm fits more closely to the adsorption data with R2 values of 0.9472, 0.9890, and 0.9684 for adsorption of Cr(VI) on Fe3O4, PANI, and PANI/Fe3O4 composites, respectively, while for adsorption of Ni(II) these values were 0.9366, 0.9232, and 0.9307 respectively. The effects of solution pH, initial concentration, contact time, ionic strength, and adsorbent dosage on adsorption behavior were investigated. The adsorption ability of composites was compared with pristine PANI and Fe3O4 particles. Activation energy and other thermodynamic properties such as changes in enthalpy, entropy, and Gibbs free energy indicated spontaneous and exothermic adsorption.