Wastewater containing polluting nanoparticles during purification is an emerging concern that has created the need to develop more efficient methodologies of wastewater treatment. Therefore, this ...contribution provides a study regarding the removal of gold and silver nanoparticles stabilized with poly(vinylpyrrolidone) (AuNP-PVP and AgNP-PVP) using flocculation at concentrations of 1.5 and 7.5–8 mg/L in kaolin aqueous dispersions. With this goal in mind, chitosan was grafted with poly(N-vinylcaprolactam)(PNVCL) and poly(acrylic acid)(PAAc) (CS-g-PNVCL, CS-g-PNVCL-PAAc), which was verified by characterization using NMR-spectroscopy, thermogravimetric analysis, dynamic light scattering, and zeta potential measurements. At pH 7, the graft copolymers presented a lower zeta potential than chitosan (close to zero), and the PVP-stabilized nanoparticles exhibited a negative surface charge (around −20 mV). The bridging mechanism during the flocculation process was discovered to be responsible for improving the performance of chitosan using chitosan-based graft polymers with low concentration (0.5 mg/L). CS-g-PNVCL-PAAc allowed higher turbidity reduction (82%), while CS-g-PNVCL was the best flocculant in nanoparticle removal (94% from 7.5 mg/L), at room temperature. The flocculants showed higher ability towards the removal of AgNP-PVP, as compared to AuNP-PVP. By increasing the temperature to 45 °C, the turbidity removal increased, while the nanoparticle removal only improved when the CS-g-PNVCL-PAAc flocculant was used. The effectiveness of chitosan-based flocculants for the removal of metallic nanoparticles as emerging contaminants is reported for the first time. Besides, the removal efficiency of metallic nanoparticles by flocculation is superior as compared to adsorption methods.
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•Flocculation performance of chitosan was surpassed by chitosan-based graft copolymers.•A low flocculant dosage of 0.5 mg/L was enough for removal of AuNP and AgNP.•The bridging mechanism was identified as being responsible for nanoparticles removal.•Flocculant CS-g-PNVCL allowed high AgNP-PVP removal: 94% from 7.5 mg/L in 60 min
Anion exchange ionomer (AEI) is a critical component used on anion exchange membrane fuel cell (AEMFC) and alkaline water electrolyzer (AWE). In this work, quaternized polysulfone with different ...functionalization degree were used as an ionomer to evaluate the performance in the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), both implied in the operation of AEMFC and AWE. The synthesized ionomer exhibited a better performance in both reactions in comparison to the commercial AEI Aemion®. PSf‐130 exhibited better performance, since IEC and surface area increases twice regarding the same parameters in the PSf‐60. The PSf‐130 conductivity increases three times regarding the value exhibited by PSf‐60. Finally, the Jlim and Jk increases 67% and 100% for ORR. On the other hand, the same catalytic parameter increased 44% and 35% for HOR comparing both polysulfone‐based ionomers. The Tafel slope values do not showed drastically changes for different ionomers indicating the same rate determining step (RDS) and the same mechanism in both reactions for all the ionomers.
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•Monomeric carbamoylcarboxylic ligands have great capacity to heavy metal ions removal.•Carbamoylcarboxylic ligands exhibit a good six-heavy metal ions simultaneous removal.•Chemical ...structure of carbamoylcarboxylic ligands influences their removal efficiency.•Instability phenomena in flocs evolution are the sedimentation and clarification.•Carbamoylcarboxylic ligands are biodegradable materials.
In this work, a library of new aniline and pyridyl functionalized carbamoylcarboxylic acids were synthesized, physicochemically analyzed and evaluated as ligands for the simultaneous removal of environmental interest cations. The effect of the structural characteristics of these functionalized ligands over the simultaneous removal performance of metal ions (Cr3+, Pb2+, Cd2+, Cu2+, Ni2+, Zn2+ and Ca2+) was established. The metal ion-ligand association constants calculated from zeta potential (102 to 104 M−1) and UV–vis (103 to 107 M−1) demonstrate a strong affinity of these ligands towards metal ions. The micro-Jar test for cation removal shows these new functionalized carbamoylcarboxylic acids L1-L12 show average removal efficiencies of 100 % Cr3+, 73 % Pb2+, 42 % Zn2+, 50 % Ni2+, 42 % Cd2+, 39 % Cu2+ and 30 % Ca2+. The quantification of destabilization phenomena through transmittance and backscattering measurements allowed to evaluate the mechanisms of colloidal instability to all ligands. Among the twelve ligands, L9 showed the best removal performance at pH = 4.0 with an overall removal capacity (19.28 mg Mn+ removed/mg of L9), clarification kinetics (55.99 T%/h) and sedimentation ratio (117.6 mm/h). The flocs recovered from the coagulation-flocculation tests were analyzed by scanning electron microscopy and dispersive energy spectroscopy with mapping finding the dispersion patterns of metals on the surface. A BOD5/COD = 0.44 indicates that L9 is a biodegradable compound. Based on the results, aniline and pyridyl functionalized carbamoylbenzoic acids have great potential to be applied in the wastewater treatment industry containing multiple cations.
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•Grafting with CCA changes solubility, porosity, ζ potential limits and IEP of chitosan.•CCA-chitosan displays a synergic performance for heavy metals removal from ...wastewater.•CCA-chitosan performs a fast clarification at lower doses than chitosan.•CCA-chitosan has potential for technological applications in wastewater treatment industry.
Water contamination by heavy metals is reported all over the world and requires strategic solutions to minimize its environmental impact. In this work, new materials based on chitosan (Q) were grafted with new mono carbamoylcarboxylic acids (mCCA) 1a and 1b were evaluated in the simultaneous removal of six metal ions by coagulation-flocculation process. The physicochemical properties and the interaction of carbamoylcarboxylic acid (CCA)-chitosans Q-1a and Q-1b, chitosan, 1a and 1b with metal ions were analyzed by zeta potential (ζ). CCA-chitosan Q-1a-5 shows significant removal of Cu2+ (99.8 %), Ni2+ (73.1 %) and Zn2+ (67.0 %) and optimal removal dose (ORD) of 20.0 mg/g of M2+, as well as Q-1b-10 performs the removal of Pb2+ (98.8 %), Cu2+ (99.1 %) and Ni2+ (81.1 %) with an ORD of 23.0 mg/g of M2+. The global metal ions removal is 81.2 % with Q-1a-5 and 79.3 % for Q-1b-10, highly superior than chitosan (42.3 % and ORD 34.3 mg/g of M2+). CCA-chitosan Q-1a-5 and Q-1b-10 show an improved clarification kinetics (18.3 and 56.8 T%/h, respectively), sedimentation ratio (10.6 and 48.5 mm/h, respectively) and a Turbiscan Stability Index (TSI) value (40.2 and 80.2, respectively) and the metal ions removal is associate to a sedimentation, flocculation and coalescence phenomena, displaying the best characteristics for the wastewater treatment containing different metal ions.
We prepared nanocrystalline mesoporous anatase-phase TiO
2
doped in the range from 0.0 to 1.0 at.% of Nd
3+
by the reverse microemulsion method (RMM). The analysis of electron microscopy of the ...nanocrystal revealed a truncated-tetragonal bipyramidal shape and agglomerates of spheroidal nanoparticles with inter-particle porosity. The inductively coupled plasma (ICP) technique corroborated the doping concentrations. The analysis of structural parameters by the Rietveld refinement technique indicated the variation of Ti–O
(1)
and Ti–O
(2)
bond lengths, suggesting the Nd
3+
insertion in the lattice. The microstructural analysis by the Williamson–Hall plot (WH) and whole powder pattern fitting (WPPF) revealed that the doping addition has a slight inhibition effect on the crystal size (6–8 nm) with a minor strain increment. The surface analysis from N
2
adsorption/desorption isotherms showed that the incorporation of the dopant in low amounts improved the mesoporous structure stability, increased the diameter of opening pores, and changed the pore structure network. The XPS analysis of the chemical states on the surface suggests that the Nd
3+
presence changed the Ti 2
p
region and the presence of the two chemical states of oxygen (O
I
and O
II
).
Polysulfone (PSF) and smart polymers (SRPs)—including polyacrylic acid (AAc), poly N-isopropylacrylamide (NIPA), and sulfonated poly(1,4-phenylene ether-ether-sulfone) (SPEES)—were used in the ...synthesis of responsive membranes (PSF-SRP) for application in sustainable desalination processes involving food industry effluents for water recovery and recycling. With the inclusion of SRPs, PSF-SRP membranes showed different characteristics when compared to the PSF membrane. AAc caused fibers to occur in the surface structure, increasing the MWCO of the PSF membrane, whereas NIPA and SPEES diminished the MWCO, resulting in ultrafiltration and nanofiltration membranes. Furthermore, NIPA and SPEES provided high mechanical and thermal resistance when incorporated into the PSF membrane. The performance of the membranes also showed important changes. In comparison with only PSF, PSF-SPEES and PSF-NIPA increased the water flux and salt rejection percentage by 20–30%. In addition, the highest membrane fouling resistance was observed with PSF-NIPA, while PSF-AAc and PSF-NIPA-AAc presented the lowest resistances. Therefore, PSF-NIPA and PSF-SPEES resulted in membrane improvement, including stimuli-responsive properties, allowing for effective saline effluent treatment.
In the present work, chemically modified graphene oxide (GO) was incorporated as a crosslinking agent into thin-film composite (TFC) nanofiltration (NF) membranes for water desalination applications, ...which were prepared by the interfacial polymerization (IP) method, where the monomers were piperazine (PIP) and trimesoyl chloride (TMC). GO was functionalized with monomer-containing groups to promote covalent interactions with the polymeric film. The composite GO/polyamide (PA) was prepared by incorporating amine and acyl chloride groups into the structure of GO and then adding these chemical modified nanomaterial during IP. The effect of functionalized GO on membrane properties and performance was investigated. Chemical composition and surface morphology of the prepared GO and membranes were analyzed by thermogravimetric analysis (TGA), Raman spectroscopy, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The fabricated composite membranes exhibited a significant increase in permeance (from 1.12 to 1.93 L m−2 h−1 bar−1) and salt rejection for Na2SO4 (from 95.9 to 98.9%) and NaCl (from 46.2 to 61.7%) at 2000 ppm, when compared to non-modified membranes. The amine- and acyl chloride-functionalized GO showed improved dispersibility in the respective phase.
A Gamma irradiation and photochemical crosslinking/grafting of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(2-hydroxyethyl methacrylate-co-poly(ethylene glycol) methacrylate) ...(poly(HEMA-co-PEGMA)) hydrogels onto polyethyleneterephtalate fabric (PET) surfaces were evaluated, in order to obtain a hydrophilic homogeneous coating onto PET fabrics. The materials were characterized by FTIR-ATR, SEM, EDS, and thermal analysis. Furthermore, silver nanoparticles (AgNPs) were loaded by in situ reduction of AgNO3, and its antibacterial activity against Staphylococcus aureus and Escherichia coli was determined. Results showed a ticker coating of hydrogel using gamma radiation and stronger in deep modification of the fibers; however, by the photochemical method, a thin coating with good coverage of PET surface was obtained. The differences in hydrophilicity, thermal properties, and antibacterial activity of the coated fabrics by using both methods were rather small.
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