Polyacrylic Acid Sodium Research Articles

Computation fluid dynamic simulation and experimental validation of shear induce dissociation coupling ultrafiltration technology for the treatment of lead contained wastewater

A novel technology, shear induced dissociation coupling with ultrafiltration (SID-UF), is used to for the treatment of lead contained wastewater for the first time. Two kinds of water soluble polymer, poly(acrylic acid) sodium (PAAS) and copolymer of maleic acid and acrylic acid (PMA), are used as complexants. The mass ratio of polymer to metal ions (P/M), pH and rotary speed are optimized by full recycle processes. The experimental results reveal that the critical shear rate of the PMA-Pb complex is less than that of the PAA-Pb complex at the same pH, that is to say, PMA-Pb complex is less stable than PAA-Pb complex in the shear field. The velocity field and shear field are simulated by CFD. Moreover, the quantum chemical computation and the frontier molecular orbitals also demonstrates that the PMA-Pb complex shows a lower energy gap than that of PAA-Pb complex. Furthermore, the reuse of complexant is achieved by shear enhance diafiltration. PMA is better for the treatment of lead contained wastewater by SID-UFdue to its higher load capacity of Pb (II) and easier regeneration.

Recovery of metals and complexant in wastewater by shear induced dissociation coupling with ultrafiltration

ABSTRACTHeavy metals (Pb (II), Hg (II), and Cd (II)) in ore dressing wastewater (ODW) were selectively separated by shear‐induced dissociation coupling with ultrafiltration (SID‐UF) using polyacrylic acid sodium (PAAS) as complexant. Metals (Pb (II), Hg (II), and Cd (II)) were complexed with PAAS and rejected by ultrafiltration membrane at first. The effects of pH and P/M (mass ratio of polymer to metal ions) on the rejection were investigated and the suitable pH and P/M were obtained, at which the rejection arrived at almost 100%. For the recovery of metals and polymer complexant from the retained, the shear stabilities of PAA‐metal (PAA‐M) complexes were studied, and the critical shear rates of PAA‐Pb, PAA‐Hg, and PAA‐Cd complexes at pH 7.0 were 2.72 × 10,5 2.42 × 105 and 2.01 × 105 s−1, respectively. According to the difference of the critical shear rates of the PAA‐M complexes, SID‐UF was used to recover Pb (II), Hg (II), Cd (II) and PAAS. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48854.

Supercooling characteristics of mannitol phase transition system under heterogeneous nucleation

Supercooling of phase change materials (PCMs) during solidification is a major problem in cold thermal energy storage (CTES), which reduces energy efficiency and aggravates energy waste. This study focuses on the supercooling characteristics of PCMs under heterogeneous nucleation, which provides a new idea for researching the influence of different dispersants on the supercooling degree of aqueous solution. The optimal ratios of CNTs water dispersant (TNWDIS) and polymer polyacrylic acid sodium (PAAS) to multi-walled carbon nanotubes (MWCNTs) in mannitol aqueous solution are determined through microstructure and cooling characteristics. How these two surfactants and MWCNTs with different concentrations and particle sizes influence the supercooling degree of nanofluids are investigated. The results indicate that the effect of PAAS is greater than that of TNWDIS. Furthermore, under the action of two dispersants and particle sizes of MWCNTs, the fitting equations of supercooling changing with the concentration of MWCNTs are obtained. In the light of the heterogeneous nucleation theory, with the enlargement of the particle size and the diminution of the contact angle affected by the dispersants, the interfacial free energy of heterogeneous nucleation of PCMs on the surface of nanoparticles is reduced. The supercooling degree therefore decreases. Specifically, the nucleation mechanism is deduced and analyzed through the contact angle and nucleation free energy formula.

Selective separation and recovery of heavy metals from electroplating effluent using shear-induced dissociation coupling with ultrafiltration

Shear-induced dissociation coupling with ultrafiltration (SID-UF) is an efficient and environment-friendly technology for the separation of heavy metal ions. In this paper, SID-UF was successfully employed for the selective recovery of nickel, zinc and copper from electroplating effluent using poly (acrylic acid) sodium (PAAS) and copolymer of maleic acid and acrylic acid (PMA) as complexants, respectively. The effects of the pH, mass ratio of polymer to metal ions (P/M) and the rotating speed on the metals removal efficiency are discussed in detail. The shear stabilities of the polymer-metal complexes were explored and the complexes critical shear rates (γc) were calculated. The results show that the order of the shear stabilities of PAA-metal complex is PAA-Zn > PAA-Cu > PAA-Ni, and that of PMA-metal complex is PMA-Cu > PMA-Ni > PMA-Zn. In addition, the construction of the stable structures of complexes and the calculation of the energies of the frontier molecular orbital by density functional theory method further predict and confirm the shear stabilities of the polymer-metal complexes.

Removal of Co(II) from aqueous solution by complexation−ultrafiltration and shear stability of PAA−Co complex

Abstract Removal of Co(II) from aqueous solutions by complexation−ultrafiltration was investigated using polyacrylic acid sodium (PAAS) as complexing agent with the help of rotating disk membrane, and the shear ability of PAA−Co complex was studied. The effects of the mass ratio of PAAS to Co(II) (P/M) and pH on the rejection of Co(II) were studied, and the optimum conditions were P/M=8 and pH=7. The rejection of Co(II) was over 97% when the rotating speed of the disk (n) was less than 710 r/min at the optimum P/M and pH. The distribution of the forms of cobalt on the membrane surface was established by the membrane partition model, and the critical shear rate, the smallest shear rate at which the PAA−Co complex begins to dissociate, was calculated to be 1.4×104 s−1, and the corresponding rotating speed was 710 r/min. The PAA−Co complex dissociated when the shear rate was greater than the critical one. The regeneration of PAAS and recovery of Co(II) were achieved by shear-induced dissociation and ultrafiltration.

Cobalt, copper and nickel-embedded chitosan/PAAS composite nanofiber mats as efficient heterogeneous catalysts for air oxidation of benzoin to benzil

We have applied electrospinning technique to embed cobalt, copper and nickel catalysts inside chitosan (CS) and polyacrylic acid sodium salt (PAAS) composite nanofiber mats (M@CS/PAAS) (M = Co2+, Cu2+ and Ni2+) as stable heterogeneous catalysts. Scanning electron microscopic analysis shows that the resultant M@CS/PAAS composite mats are bead-free and cylindrical nanofibers with mean diameter ranging from 474 to 504 nm, and the incorporated transition metal catalysts are homogeneously distributed inside the nanofibers in tight chelation with the chitosan amine groups. The M@CS/PAAS nanofiber mats exhibited excellent catalytic activity for atmospheric air oxidation of benzoin to benzil, and are much more stable than those prepared by conventional wetness impregnation (M-CS/PAAS nanofiber mats). Moreover, their catalytic activities and stabilities could be further enhanced by introduction of additional ligands through Schiff base transformation of the chitosan pendant amine groups. The free volume holes of the nanofibers were estimated to be considerably larger than the reactant and product molecules, allowing them to freely migrate around the internal catalytic sites. Taken together, we have demonstrated a straightforward approach to prepare efficient and recyclable heterogeneous catalysts derived from the first-row transition metal catalysts by entrapping them inside the chitosan/PAAS composite nanofibers.

Preparation of epoxidized acrylonitrile butadiene rubber and its compatibilization effect on water‐swellable rubber composites

ABSTRACTIn this research, water‐swellable rubbers (WSRs) were prepared by the blending of acrylonitrile butadiene rubber (NBR) with epoxidized acrylonitrile butadiene rubber (ENBR), precipitated silica, vulcanizing agents, and polyacrylic acid sodium (PAAS) as superabsorbent polymers (SAPs). ENBR was prepared with a molybdenum trioxide catalyst and a tert‐butyl hydroperoxide oxidant through a free‐radical reaction under specific conditions and was used as a compatibilizer to improve the interfacial adhesion of the NBR matrix and hydrophilic components of the WSRs. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy were used to analyze the structure and properties of ENBR. The dispersion of silica and SAPs in the rubber matrix was investigated by transmission electron microscopy. The presence of ENBR enhanced the water‐absorption properties of the WSRs. The NBR–ENBR composites exhibited a higher mechanical performance after water absorption than that without ENBR. Both the swelling ratio and the absorption rate increased with the ENBR content. When the weight ratio of NBR–ENBR was 25/75, an equilibrium swelling ratio of 172% (13% higher than that of the sample without ENBR) was obtained. Scanning electron microscopy analysis revealed that the addition of ENBR improved the compatibility between the SAPs and the NBR matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47694.

Pretreatment of poly (acrylic acid) sodium by continuous diafiltration and time revolution of filtration potential

The pretreatment for the removal of small molecules from poly(acrylic acid) sodium (PAAS) solution by continuous diafiltration was investigated using ultrafiltration membrane. The effects of PAAS concentration, pH, trans-membrane pressure and pretreatment time on the permeate concentration and permeate flux were studied. The results show that the necessary pretreatment time (NPT) increases with PAAS concentration, decreases with TMP. The change trend of permeate flux with time is affected by pH. The permeate fluxes rapidly decrease from the start, and then increase gradually to stable values at pH 5.0, pH 7.0 and pH 9.3. However, it decreases gradually with time till a state value at pH 3.0 (iso-electric point, IEP). The removal of small molecules is easy at pH greater than iso-electric point (IEP). The change of filtration potential with time indicates the similar trend to that of permeation concentration, but the former is more convenient for indication of NPT.

Recyclable magnetic NiFe2O4/C yolk-shell nanospheres with excellent visible-light-Fenton degradation performance of tetracycline hydrochloride.

A photo-Fenton-like reaction was considered as an effective method for wastewater treatment because it could produce more oxidative species such as hydroxyl radicals (˙OH) to accelerate the reaction. In this paper, a NiFe2O4/C (abbr. as NFO/C) yolk-shell nanostructure was synthesized via one-step calcination using polyacrylic acid sodium salt (PAAS) NPs as a template. The nanocomposite was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption, among others. The magnetically separable nanocomposite exhibited a high activity and recyclability towards the photodegradation of tetracycline hydrochloride (TC). In addition, the factors affecting the photodegradation process were systematically investigated, including the dosage of the NiFe2O4/C catalyst, the pH of the solution, and the volume of H2O2. Notably, the degradation rate of tetracycline hydrochloride (TC) reached 97.25% in 60 min in the presence of H2O2 under visible light irradiation (λ > 400 nm) with NiFe2O4/C. This work provides a simple and novel method to construct NiFe2O4/C yolk-shell nanostructures, which may be applied to the photodegradation of tetracycline hydrochloride from wastewater. Finally, a photocatalytic and stability mechanism is proposed, which may help us more comprehensively understand the photo-Fenton mechanism.

Improved electrochemical performance of LiCoPO4 using eco-friendly aqueous binders

The electrochemical performance of LiCoPO4 (LCP) as a high-voltage positive electrode for lithium-ion batteries is significantly improved by using the aqueous binder sodium carboxymethyl cellulose (CMC). The CMC not only provides a uniform electrode surface as shown by scanning electron microscopy and elemental mapping, but also suppresses the degradation of LiCoPO4 by scavenging HF in the electrolyte solution as demonstrated by FT-IR. In comparison with other water-soluble binders such as sodium alginate (ALG) and polyacrylic acid sodium salt (PAA), the homogeneous distribution of CMC within the electrodes accompanied by high accessibility of carboxylate groups in CMC are shown to be crucial factors to achieve enhanced performance with an excellent capacity retention of 94% after 20 cycles at a rate of C/10.

Removal of Zn (II) by complexation-ultrafiltration using rotating disk membrane and the shear stability of PAA-Zn complex

Polyacrylic acid sodium (PAAS) was applied to remove Zn (II) from aqueous solutions by complexation-ultrafiltration using a rotating disk membrane module. As important factors, solution pH and the mass ratio of polymer to metal ions (P/M) on the rejection of Zn (II) were investigated, and the rejection could reach to 95.3% at pH=7, P/M=25 and 500 rpm. In addition, a partition model was proposed to reveal instability mechanism of the PAA-Zn complex in the shear field for the first time. The critical rotating speeds at which PAA-Zn complexes begin to dissociate were 1,460, 1,390, 1,280 rpm at pH 7.0, 6.0, 5.0, respectively. The corresponding critical shear rates (γc), the smallest shear rates at which PAA-Zn complex begins to dissociate, were 1.58×105, 1.45×105 and 1.25×105 s-1 at pH 7.0, 6.0, 5.0, respectively. In addition, the relationship between the critical radii and the critical rotating speed was obtained.

Removal of heavy metal chromium using cross-linked chitosan composite nanofiber mats

Uniform chitosan composite nanofiber mats (CS/PAAS) containing 4.0 wt% polyacrylic acid sodium loading have been prepared by electrospinning, followed by annealing at elevated temperature to improve solvent resistance and mechanical strength. The CS/PAAS nanofiber mats have been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and tensile strength analysis. The prepared nanofiber mats have been shown to be much better than the pristine chitosan powder to adsorb the chromium (VI) ion. SEM-Energy dispersive X-ray spectroscopic (SEM-EDS) and positron annihilation lifetime spectroscopic (PALS) analysis show that Cr(VI) ion can freely permeate into the composite nanofiber and coordinate with the internal chitosan chain molecules. The adsorption abilities of these cross-linked CS/PAAS nanofiber mats are dependent on the chitosan contents as well as N-atom basicity of the chitosan chain. The adsorption capacity toward Cr(VI) ion was improved to 78.92 mg/g after modification of the chelating ligands for the cross-linked CS/PAAS composite nanofibers.

Removal of Cd (II) from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane and the shear stability of PAA–Cd complex

Abstract Removal of cadmium (II) ions from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane was investigated. Polyacrylic acid sodium (PAAS) was used as complexation agent, as key factors of complexation, pH and the mass ratio of PAAS to Cd2 + (P/M) were studied, and the optimum complexation–ultrafiltration conditions were obtained. The effects of rotating speed (n) on the stability of PAA–Cd complex was studied with two kinds of rotating disk, disk I (without vane) and disk II (with six rectangular vanes) at a certain range of rotating speed. Both of the rejection could reach 99.7% when n was lower than 2370 r·min− 1 and 1320 r·min− 1, for disk I and disk II, respectively. However, when rotating speed exceeds a certain value, the critical rotating speed (nc), the rejection of Cd (II) decreases greatly. The distribution of form of cadmium on the membrane was established by the membrane partition model, and the critical shear rate (γc), the smallest shear rate at which the PAA–Cd complex begins to dissociate, was calculated based on the membrane partition model and mass balance. The critical shear rates (γc) of PAA–Cd complex were 5.9 × 104 s− 1, 1.01 × 105 s− 1, and 1.31 × 105 s− 1 at pH = 5.0, 5.5, and 6.0, respectively. In addition, the regeneration of PAAS was achieved by shear induced dissociation and ultrafiltration.

Removal of Cu (II) From Aqueous Solution by Rotating Disk Shear Enhanced Complexation-Ultrafiltration

The polyacrylic acid sodium (PAAS) has been applied into the removal of Cu (II) from aqueous solutions by a rotating disk shear enhanced complexation-ultrafiltration process. As important factors, solution pH and polymer/metal mass ratio (P/M) on the rejection of Cu(II) have been investigated, the removal rate of Cu (II) can reach 99.6% at suitable condition, pH=6.0, P/M=25. The permeate flux increases from 38.5 to 47.2 L m·2kPa·1h·1 with the increase of rotating speed from 0 to 3000 rpm. However, the rejections of Cu (II) decrease sharply when the rotating speeds are more than 700, 900, 1000 rpm at pH values 4.0, 5.0, 6.0, respectively. Thus, only at suitable rotating speed, can high permeate flux and removal rate be obtained for shear enhanced complexation-ultrafiltration.

Removal of copper(II) ions from aqueous solutions by complexation–ultrafiltration using rotating disk membrane and the shear stability of PAA–Cu complex

The stability of polymer–metal complex in the shear field is of great significance for the industrial applicaion of complex-ultrafiltration. The shear stability of PAA–Cu complex was investigated for the first time. Polyacrylic acid sodium (PAAS) was applied to remove Cu(II) from aqueous solutions by complexation–ultrafiltration using a rotating disk membrane. As important factors, solution pH and P/M (the mass ratio of polymer to metal ions) on the rejection of Cu(II) were investigated, and the rejection of Cu(II) could reach 99.6% at pH=6.0, P/M=25. The rotating disk was applied to generate shear rate on the membrane surface, and the radial distribution of shear rate on the membrane surface was calculated. The critical rotating speeds at which the rejection of Cu(II) begins to decrease were 1000, 900, 700rpm at pH values 6.0, 5.0, 4.0, respectively, and the corresponding critical shear rates (γc) at which the PAA–Cu complex begins to dissociate were 8.0×104, 6.6×104 and 4.2×104s−1, respectively. Furthermore, the critical shear radius and the radial distribution of substances on the membrane surface were obtained using a segmentation model. The shear stability, especially the critical shear rate of the polymer–metal complex, can give guidance to the selection of the delivery pumps so that high removal efficiency can be obtained in the industrial application of complexation–ultrafiltration. In addition, shear induced dissociation and ultrafiltration was first applied to regenerate PAAS.

Zn(II) porphyrin-based photocatalytic synthesis of Cu nanoparticles for electrochemical reduction of CO2

Copper nanoparticles frequently exhibit unique electrocatalytic activity for the electrochemical reduction of carbon dioxide. However, the synthesis of Cu nanoparticles in aqueous systems remains rare. Herein, we report the synthesis of copper nanoparticles by using a zinc(II) porphyrin-based photocatalytic method in the presence of polyacrylic acid sodium salt (PAA) in water under visible light irradiation, leading to a series of Cu nanoparticles with relatively small average sizes ranging from 69 to 97 nm. PAA molecules adsorbed on Cu nanoparticles were simply removed by washing with copious amount of water. The purified Cu nanoparticles show some activity toward the electrochemical reduction of carbon dioxide as evidenced by linear sweep voltammetry (LSV) and gas chromatography (GC).

A Highly Flexible Supercapacitor Based on MnO₂/RGO Nanosheets and Bacterial Cellulose-Filled Gel Electrolyte.

The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO2) and reduced graphene oxide (RGO) nanosheet-piled hydrogel films and a novel bacterial cellulose (BC)-filled polyacrylic acid sodium salt-Na2SO4 (BC/PAAS-Na2SO4) neutral gel electrolyte. Apart from being environmentally friendly, this BC/PAAS-Na2SO4 gel electrolyte has high viscosity and a sticky property, which enables it to combine two electrodes together. Meanwhile, the intertangling of the filled BC in the gel electrolyte hinders the decrease of the viscosity with temperature, and forms a separator to prevent the two electrodes from short-circuiting. Using these materials, the total thickness of the fabricated device does not exceed 120 μm. This SC device demonstrates high flexibility, where bending and even rolling have no obvious effect on the electrochemical performance. In addition, owing to the asymmetric configuration, the cell voltage of this flexible SC has been extended to 1.8 V, and the energy density can reach up to 11.7 Wh kg−1 at the power density of 441 W kg−1. This SC also exhibits a good cycling stability, with a capacitance retention of 85.5% over 5000 cycles.

Sustainable operation of osmotic microbial fuel cells through effective reproduction of polyelectrolyte draw solutes facilitated by cathodic pH increase

Osmotic microbial fuel cells (OsMFCs) take advantages of synergy between forward osmosis (FO) and microbial fuel cells (MFCs) for simultaneous wastewater treatment, bioenergy production, and water recovery. A unique feature for healthy operation of OsMFCs is an appropriate draw solute (DS) that can also act as a catholyte. Herein, polyelectrolytes (polyacrylic acid sodium salts, PAA-Na) was investigated as a DS/catholyte and reproduced with the aid of the high catholyte pH. Such a reproduction method is innovative, because it turns a drawback (high catholyte pH) into a useful resource, thereby reducing the demand for external input and leading to a clean production process. The results have showed that the OsMFC achieved a current density of 159 ± 6 A m−3, water flux of 12.7 ± 0.2 LMH, and low reverse salt flux of 0.05 ± 0.00 gMH with 32 wt% PAA-Na (2000 Da) as the DS. The DS recovery efficiency could be as high as 99.86 ± 0.04%, and the reproduced DS was successfully applied in the subsequent operation. With this reproduction method, the highest total operation cost was estimated at 0.104 $ m−3. Those results have demonstrated a new approach based on pH-dependent PAA DS reproduction towards further development of OsMFC technology for sustainable water/wastewater treatment and resource recovery.

Efficient recovery of polyelectrolyte draw solutes in forward osmosis towards sustainable water treatment

Forward osmosis (FO) technology has long been constrained by the slow development of appropriate draw solutes (DS) and the relatively high cost associated with DS recovery. In this study, a series of polyelectrolytes, polyacrylic acid sodium salts (PAA-Na) with different molecular weights, were explored as DS for FO applications with a focus on the recovery using combined pH and microfiltration (MF). The FO system achieved a high water flux of 18.02±0.51LMH, low reverse salt flux (RSF) of 0.110±0.004gMH, and the JS/JW of 6.1±0.3mgL−1 with 25wt% PAA-Na (2000Da) as the DS and DI water as the feed. The DS recovery efficiency by the combined pH+MF approach was 99.68% at pH of 4.35, and the operation cost was estimated at 0.037$m−3. Dynamic light scattering revealed that the hydrodynamic diameter of PAA increased with decreasing pH, resulting in PAA polymers precipitated as aggregates at the pH response point. The 25wt% 2000 PAA-Na achieved the water flux of 11.56±0.32LMH from synthetic seawater and 17.19±0.52LMH from the treated wastewater. These results have demonstrated efficient and cost-effective recovery of PAA DS for FO-based applications.

Preparation, characterization and application of PS/SPEES–PES UF membranes for removal of ppm Cd2+ from aqueous media

Ultrafiltration membrane prepared from hydrophobic polymers like polysulfone or polyethersulfone (PES) suffers heavy membrane fouling during cross-flow filtration. Inclusion of hydrophilic polymer like SPEES in the membrane will increase the hydrophilicity of the membrane surface, this in turn would slow down the membrane fouling process and thus prolong the service life time of the polymeric membrane. This work involves the fabrication and characterization of nine KC-series ultrafiltration membranes containing various weight percent of sulfonated polymer (SPEES) via phase-inversion process; basic characteristics of these membranes like pure water flux, water content, surface charge density, molecular weight cut-off were determined. Application of KC-series UF membranes, containing various amounts of hydrophilic polymer [sulfonated polyetherethersulfone/polyethersulfone (SPEES/PES)], for the removal of Cd2+ in ppm concentrations from aqueous media via cross-flow filtration operation was investigated. Rejection of Cd2+ from the feed containing 50 ppm in Cd2+ and 100 ppm in polyacrylic acid sodium (225 kDa) salt achieved ~100%.