Diallyldimethylammonium Chloride Research Articles

Removal of algae from ballast water by cationic flocculant-composite titanium xerogel coagulant: Differences in freshwater and seawater

The treatment of ballast water has been garnering increasing attention, with planktonic algae removal being a crucial part. Coagulation has been demonstrated as an effective method for algae removal, albeit few coagulants exhibit excellent coagulation performance in both freshwater and seawater. To address this issue, the cationic flocculant poly dimethyl diallyl ammonium chloride (PDADMAC) was composited with titanium xerogel coagulant (TXC), abbreviated as PT. Using the algae Cyclotella meneghiniana as the research object, the algal removal performance and mechanisms of PT in freshwater and seawater were investigated. Cell integrity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content of C. meneghiniana during floc storage were also evaluated. The PT composite coagulant exhibited excellent coagulation performance in both freshwater and seawater. Its algal removal ability was superior to TXC and the commercial coagulants polyaluminum chloride (PAC) and polymerized ferrous sulfate (PFS), with removal rates for C. meneghiniana reaching 98.3 % in freshwater and 98.4 % in seawater at a 80 mg/L dosage. PT also exhibited excellent removal performance over wide dosage and pH ranges. PT acted via distinct coagulation mechanisms in freshwater and seawater, with charge neutralization and bridging played major roles in freshwater and sweeping being important in seawater. The floc storage experiment indicated that the coagulation process did not directly lead to algal cell fragmentation, but PT accelerated and exacerbated oxidative stress and oxidative damage to algal cells during floc storage. Furthermore, PT also showed excellent removal performance for the marine diatom Skeletonema costatum and the freshwater cyanobacteria Cylindrospermopsis raciborskii. This work not only provides a novel approach for algae removal in ballast water, but also enhances our understanding of the coagulation behavior of titanium-based coagulants in different water environments.

Biomimetic Approach for Sustainable Magnetite Nanoparticle Synthesis Using Polycations

AbstractMagnetotactic bacteria produce magnetite nanoparticles called magnetosomes at ambient conditions via a protein‐stabilized transient amorphous precursor to obtain precise control over particle size and morphology. In a bioinspired approach, such biomineralization processes are emulated, mimicking proteins involved in magnetosome formation using the positively charged analog poly‐L‐arginine. While the additive is expensive, it remains elusive whether the change in magnetite formation mechanism arises solely from the polymer's cationic nature. This study uses different mass‐produced and sustainably sourced polycations to induce the biomineralization‐reminiscent formation of magnetite nanoparticles. These findings present how to achieve control over nanoparticle size (from 10 to 159 nm) and morphology (compact and sub‐structured) as well as magnetic properties (superparamagnetic, stable‐single‐domain, vortex state) at ambient temperature and pressure using these additives. Furthermore, the formation of large nanoparticles with the addition of poly(diallyldimethylammonium chloride) (PDADMAC) at low alkalinity highlights how magnetotactic bacteria may produce magnetite nanoparticles under similar conditions. Confirming the polycations' ability to electrostatic stabilize amorphous ferrihydrite, it is anticipated that parametric in vitro studies on polymer properties will provide valuable insights into magnetite biomineralization and aid in rationally designing magnetic nanomaterials.

Preparation of amphoteric polycarboxylate superplasticizer at low temperature and its application in cement-calcined kaolin blended system

As one of supplementary cementitious materials (SCMs), calcined kaolin (CK) has received increasing attention in the development of green and sustainable SCMs. When CK was applied into cement, the regular anionic polycarboxylate superplasticizer (PCE) is insufficient to disperse the cement-calcined kaolin blended system (CMT-CK system). Herein, a novel amphoteric polycarboxylate superplasticizer (VDA-1) was synthesized with hydroxybutyl vinyl polyoxyethylene ether (VPEG), acrylic acid (AA) and dimethyl diallyl ammonium chloride (DMDAAC) at low temperature (10 °C). Among a series of synthesized PCE samples, VDA-1 (nVPEG:nAA:nDMDAAC = 1:2.25:0.75) exhibits the best performance in the CMT-CK system. Results showed that the fluidity of the CMT-CK mixed slurry with VDA-1 increased by 127.9 % compared with pure CMT-CK slurry. Meanwhile, the mixed slurry with VDA-1 had good flow retention. The great fluidity of the mixed slurry with VDA-1 is attributed to that VDA-1 can be adsorbed on the surface of cement and calcined kaolin, which was demonstrated by total organic carbon (TOC) adsorption amount analysis. Besides, compared with pure CMT-CK system, the compressive and flexural strength of blended cement with VDA-1 was enhanced 2.26% and 10.60%, respectively. Split Hopkinson Pressure Bar (SHPB) test showed that the CMT-CK system containing VDA-1 exhibited large stress value before instability stage and the maximum absorption energy in the whole process.

Development of a label-free, sensitive gold nanoparticles-poly(adenine) aptasensing platform for colorimetric determination of aflatoxin B1 in corn.

In this work, a sensitive colorimetric bioassay method based on a poly(adenine) aptamer (polyA apt) and gold nanoparticles (AuNPs) was developed for the determination of aflatoxin B1 (AFB1). The polyA apt, adsorbed on the AuNPs, especially can bind to the analyte while deterring non-specific interactions. This nano aptasensor uses cationic polymer poly(diallyl dimethyl ammonium chloride) (PDDA), as an aggregating agent, to aggregate gold nanoparticles. PolyA apt-decorated gold nanoparticles (AuNPs/polyA apt) show resistance to PDDA-induced aggregation and maintains their dispersed state (red color) with the optical absorbance signal at λ = 520 nm. However, in the presence of AFB1 in the assay solution, the specific aptamer reacts with high affinity and folds into its three-dimensional form. Aggregation of AuNPs induced by PDDA caused their optical signal shift to λ = 620 nm (blue color). AFB1 concentration in the bioassay solution determines the amount of optical signal shift. Therefore, optical density ratio in two wavelengths (A620/520) can be used as a sturdy colorimetric signal to detect the concentration of aflatoxin B1. AFB1 was linearly detected between 0.5 and 20 ng mL-1, with a detection limit of 0.09 ng mL-1 (S/N = 3). The fabricated aptasensor was applied to the detection of AFB1 in real corn samples.

Graphene oxide-DNA/graphene oxide-PDDA sandwiched membranes with neuromorphic function.

The behavior of polyelectrolytes in confined spaces has direct relevance to the protein mediated ion transport in living organisms. In this paper, we govern lithium chloride transport by the interface provided by polyelectrolytes, polycation, poly(diallyldimethylammonium chloride) (PDDA) and, polyanion, double stranded deoxyribonucleic acid (dsDNA), in confined graphene oxide (GO) membranes. Polyelectrolyte-GO interfaces demonstrate neuromorphic functions that were successfully applied with nanochannel ion interactions contributed, resulting in ion memory effects. Excitatory and inhibitory post-synaptic currents were tuned continuously as the number of pulses applied increased accordingly, increasing decay times. Furthermore, we demonstrated the short-term memory of a trained vs untrained device in computation. On account of its simple and safe production along with its robustness and stability, we anticipate our device to be a low dimensional building block for arrays to embed artificial neural networks in hardware for neuromorphic computing. Additionally, incorporating such devices with sensing and actuating parts for a complete feedback loop produces robotics with its own ability to learn by modifying actuation based on sensing data.

Photoresponsive arylazopyrazole surfactant/PDADMAC mixtures: reversible control of bulk and interfacial properties.

In many applications of polyelectrolyte/surfactant (P/S) mixtures, it is difficult to fine-tune them after mixing the components without changing the sample composition, e.g. pH or the ionic strength. Here we report on a new approach where we use photoswitchable surfactants to enable drastic changes in both the bulk and interfacial properties. Poly(diallyldimethylammonium chloride) (PDADMAC) mixtures with three alkyl-arylazopyrazole butyl sulfonates (CnAAP) with -H, -butyl and -octyl tails are applied and E/Z photoisomerization of the surfactants is used to cause substantially different hydrophobic interactions between the surfactants and PDADMAC. These remotely controlled changes affect significantly the P/S binding and allows for tuning both the bulk and interfacial properties of PDADMAC/CnAAP mixtures through light irradiation. For that, we have fixed the surfactant concentrations at values where they exhibit pronounced surface tension changes upon E/Z photoisomerization with 365 nm UV light (Z) and 520 nm green (E) light and have varied the PDADMAC concentration. The electrophoretic mobility can be largely tuned by photoisomerisation of CnAAP surfactants and P/S aggregates, which can even exhibit a charge reversal from negative to positive values or vice versa. In addition, low colloidal stability at equimolar concentrations of PDADMAC with CnAAP surfactants in the E configuration lead to the formation of large aggregates in the bulk which can be broken up by irradiation with UV light when the surfactant's alkyl chain is short enough (C0AAP). Vibrational sum-frequency generation (SFG) spectroscopy reveals changes at the interface similar to the bulk, where the charging state at air-water interfaces can be modified with light irradiation. Using SFG spectroscopy, we interrogated the O-H stretching modes of interfacial H2O and provide qualitative information on surface charging that is complemented by neutron reflectometry, from which we resolved the surface excesses of PDADMAC and CnAAP at the air-water interface, independently.

Multilayer coatings based on gold nanoparticles and polymers with bovine serum albumin as a functional layer for the chiral separation in capillary electrochromatography.

In this study, we developed physically adsorbed multi-layer coatings using poly-l-lysine or poly(diallyldimethylammonium chloride) and gold nanoparticles, which were functionalized with bovine serum albumin for the chiral separation in electrochromatography. The approach involves sequentially depositing positively charged polymers and negatively charged citrate-stabilized gold nanoparticles. By repeating this modification cycle, we created two- and four-layer coatings, which were sequentially functionalized with albumin forming three- and five-layer coatings that were finally applied for the separation of enantiomers of dl-tryptophan. The formed coatings exhibit stability across a pH range of 2-10 and feature a dense, uniform surface, as confirmed by scanning electron microscope images. The number of layers impacted nanoparticle deposition density, with five-layer coatings being denser than three-layer ones. Five-layer coatings enable baseline separation of dl-tryptophan enantiomers, whereas three-layer coatings require the presence of albumin in the background electrolyte for separation. Therefore, increasing the number of layers and gold nanoparticles density enhances albumin active center concentration on capillary walls, improving the separation of dl-tryptophan enantiomers. The five-layer coatings can be easily fabricated and possess good repeatability of analytes migration time.

High-precision Helicobacter pylori infection diagnosis using a dual-element multimodal gas sensor array.

Helicobacter pylori (H. pylori) is a globally widespread bacterial infection. Early diagnosis of this infection is vital for public and individual health. Prevalent diagnosis methods like the isotope 13C or 14C labelled urea breath test (UBT) are not convenient and may do harm to the human body. The use of cross-response gas sensor arrays (GSAs) is an alternative way for label-free detection of metabolite changes in exhaled breath (EB). However, conventional GSAs are complex to prepare, lack reliability, and fail to discriminate subtle changes in EB due to the use of numerous sensing elements and single dimensional signal. This work presents a dual-element multimodal GSA empowered with multimodal sensing signals including conductance (G), capacitance (C), and dissipation factor (DF) to improve the ability for gas recognition and H. pylori-infection diagnosis. Sensitized by poly(diallyldimethylammonium chloride) (PDDA) and the metal-organic framework material NH2-UiO66, the dual-element graphene oxide (GO)-composite GSAs exhibited a high specific surface area and abundant adsorption sites, resulting in high sensitivity, repeatability, and fast response/recovery speed in all three signals. The multimodal sensing signals with rich sensing features allowed the GSA to detect various physicochemical properties of gas analytes, such as charge transfer and polarization ability, enhancing the sensing capabilities for gas discrimination. The dual-element GSA could differentiate different typical standard gases and non-dehumidified EB samples, demonstrating the advantages in EB analysis. In a case-control clinical study on 52 clinical EB samples, the diagnosis model based on the multimodal GSA achieved an accuracy of 94.1%, a sensitivity of 100%, and a specificity of 90.9% for diagnosing H. pylori infection, offering a promising strategy for developing an accurate, non-invasive and label-free method for disease diagnosis.

Customizing precise, tunable, and universal cascade charge transfer chains towards versatile photoredox catalysis.

The core factors dictating the photocatalysis efficiency are predominantly centered on controllable modulation of anisotropic spatial charge transfer/separation and regulating vectorial charge transport pathways. Nonetheless, the sluggish charge transport kinetics and incapacity of precisely tuning interfacial charge flow at the nanoscale level are still the primary dilemma. Herein, we conceptually demonstrate the elaborate design of a cascade charge transport chain over transition metal chalcogenide-insulating polymer-cocatalyst (TIC) photosystems via a progressive self-assembly strategy. The intermediate ultrathin non-conjugated insulating polymer layer, i.e., poly(diallyl-dimethylammonium chloride) (PDDA), functions as the interfacial electron relay medium, and simultaneously, outermost co-catalysts serve as the terminal "electron reservoirs", synergistically contributing to the charge transport cascade pathway and substantially boosting the interfacial charge separation. We found that the insulating polymer mediated unidirectional charge transfer cascade is universal for a large variety of metal or non-metal reducing co-catalysts (Au, Ag, Pt, Ni, Co, Cu, NiSe2, CoSe2, and CuSe). More intriguingly, such peculiar charge flow characteristics endow the self-assembled TIC photosystems with versatile visible-light-driven photoredox catalysis towards photocatalytic hydrogen generation, anaerobic selective organic transformation, and CO2-to-fuel conversion. Our work would provide new inspiration for smartly mediating spatial vectorial charge transport towards emerging solar energy conversion.

Dilution-controlled deposition of mixtures of a synthetic polycation and a natural origin polyelectrolyte with anionic surfactants on negatively charged surfaces

The cosmetics industry is constantly seeking sustainable and environmentally friendly ingredients for hair care formulations to replace those traditionally derived from the petrochemical industry. In this context, the substitution of traditional cationic polyelectrolytes, such as poly(diallyldimethylammonium chloride, PDADMAC), by others of natural origin, such as chitosan, is a key challenge to achieve new formulations with a higher degree of naturality and more environmentally friendly without compromising product efficacy. This work investigates the effect of dilution on the phase separation of concentrated binary mixtures of two anionic surfactants (sodium laureth sulfate, SLES, and sodium dodecyl sulfate, SDS) with PDADMAC or chitosan. PDADMAC is a polycation of petrochemical origin, whereas chitosan is obtained from natural resources. Also, how this phase separation affects the formation of conditioning deposits on surfaces that mimic the charge and wettability of damaged hair fibers has been studied. The results show that for polymers of similar molecular weight, the substitution of PDADMAC by a highly charged chitosan is a promising alternative. The deposition is greatly enhanced for model wash formulations containing chitosan after minimal dilution. The results obtained here may pave the way to an important line of research toward improving the sustainability profile of hair care formulations without compromising consumer satisfaction.

A bioinspired approach for the modulation of electroosmotic flow and protein-surface interactions in capillary electrophoresis using silylated amino-amides blocks and covalent grafting.

We explore a bioinspired approach to design tailored functionalized capillary electrophoresis (CE) surfaces based on covalent grafting for biomolecules analysis. First, the approach aims to overcome well-known common obstacles in CE protein analysis affecting considerably the CE performance (asymmetry, resolution, and repeatability) such as the unspecific adsorption on fused silica surface and the lack of control of electroosmotic flow (EOF). Then, our approach, which relies on new amino-amide mimic hybrid precursors synthesized by silylation of amino-amides (Si-AA) derivatives with 3-isocyanatopropyltriethoxysilane, aims to recapitulate the diversity of protein-protein interactions (π-π stacking, ionic, Van der Waals…) found in physiological condition (bioinspired approach) to improve the performance of CE protein analysis (electrochromatography). As a proof of concept, these silylated Si-AA (tyrosinamide silylation, serinamide silylation, argininamide silylation, leucinamide silylation, and isoglutamine silylation acid) have been covalently grafted in physiological conditions in different amount on bare fused silica capillary giving rise to a biomimetic coating and allowing both the modulation of EOF and protein-surface interactions. The analytical performances of amino-amide functionalized capillaries were assessed using lysozyme, cytochrome C and ribonuclease A and compared to traditional capillary coatings poly(ethylene oxide), poly(diallyldimethylammonium chloride), and sodium poly(styrenesulfonate). EOF, protein adsorption rate, protein retention factor k, and selectivity were determined for each coating. All results obtained showed this approach allowed to modulate the EOF, reduce unspecific adsorption, and generate specific interactions with proteins by varying the nature and the amount of Si-AA in the functionalization mixture.

Development of composite polyelectrolyte complex membranes as cathodes for aqueous zinc-ion batteries

Zinc-ion batteries (ZIBs) are an interesting alternative to lithium batteries due to their high specific capacity, eco-friendly properties, and ease of processing. Cathodes are an essential component of ZIBs that provide electron storage capacity. In this study, composite polyelectrolyte complexes (C-PECs) made from cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic poly(sodium-4-styrenesulfonate) (PSS), along with carbon blacks N550 and layer-structured δ-MnO2 were used to create ZIB cathodes. Interestingly, various salt ions content (0, 1, 2 M NaCl), used as plasticizer to induce softening of the C-PEC at the processing stage were found to strongly affects the cathode’s performance. Results show that the composite exhibited an optimum battery specific capacity of approximately 7.78 mA cm−2.

Smart Composite Coatings for Corrosion Protection

Corrosion is a major problem faced by the automobile industry. To overcome corrosion, the industry relies on surface coatings in which metallic (Zn, Cr etc.) and polymeric coatings (polyurethane, epoxy, etc.) are widely recommended. However, currently smart, self-healing coatings are considered to be the state of the art option to inhibit cut-edge corrosion and to enhance the life-time. The direct introduction of inhibitors into any matrix creates undesirable effects, majorly the integrity of the inhibitor with the matrix and spontaneous release. Hence, loading inhibitors into a suitable container and subsequent release of the same when the coating is damaged favors the self-healing property of a coating, which results in high durability.Such a smart coating can be achieved by the synthesis of porous silica particles, which can be an effective corrosion inhibitor container. They possess exceptional properties like nontoxicity, high surface area, and capability to be filled with different types of active materials, including organic, inorganic, and hybrid inhibitors. Hence, these can be the equivalent and non-toxic alternative to chromates which are toxic and carcinogenic to the environment and the living system.Among the different porous containers reported in the literature, mesoporous silica nanoparticles have large surface area which is beneficial to load the required quantity of corrosion inhibitors. The corrosion inhibitor-loaded porous silica containers are compatible with different matrices, including metals, polymers, and ceramics, to prepare the composite materials. To control the instant release of the loaded inhibitors, encapsulation with a polyelectrolyte is required. As a result, improved self-healing properties can be achieved as compared to the particles without encapsulation.Among the various types of porous silica, Santa Barbara Amorphous-15 (SBA-15) has several benefits, including the ease of preparation, nontoxic precursors, hexagonal structure to carry a high quantity of material, size range from micro to nanometer, controllable pore size (20-500Å), large specific surface area (∼1000m2/g), porosity, surface morphology and huge pore volume. This work describes the synthesis of mesoporous silica (SBA-15) using a three-step solvo-thermal process. The process includes template preparation (synthesis of mesoporous silica), loading with benzotriazole (BTA) an organic corrosion inhibitor, followed by Poly(diallyldimethylammonium chloride) (PDDA) encapsulation.The synthesised mesoporous silica was characterised for morphological features, porosity, and surface charge. Based on the BET analysis, successful modification of the mesoporous silica particles at different stages shows a reduction in the surface area and pore volume. The zeta (ζ)-potential measurements showed a significant variation in surface charge after the modification of the mesoporous silica particles. The releasing nature of BTA before and after the PDDA encapsulation was studied using UV-Visible technique at different pH levels. Based on the characterisation of the PDDA encapsulated inhibitor-loaded mesoporous silica particles, appropriate coating was prepared by incorporating these particles into eg. metallic (Zn coating) and/or polymeric (epoxy coating) matrices. The release and corrosion inhibition performance of these coatings were studied using electrochemical techniques. The multi-functional performance of these coatings would be highlighted.

Layered Nanocomposites of Polymer-Functionalized Reduced Graphene Oxide and Borocarbonitride with MoS2 and MoSe2 and Their Hydrogen Evolution Reaction Activity

Two dimensional heterostructure have been widely investigated for various applications in electrochemistry such as water splitting and battery storage. These heterostructures are mainly formed due to vander waals interaction, covalent cross-linking and electrostatic interactions. Herein, we have prepared nanocomposite of positively charged poly (diallyldimethylammonium chloride) (PDDA, shown as P)-functionalized reduced graphene oxide (RGO) and borocarbonitride (BC6N, shown as BCN for simplicity) sheets with layers of negatively charged MoS2 and MoSe2 by electrostatic interaction in solution phase. The nanocomposites exhibit superior photocatalytic hydrogen evolution reaction (HER) activity compared to the individual components, and the value increases with the MoS2/MoSe2 content. The highest photocatalytic HER activity obtained is 11230 μmol h–1 g–1 in the nanocomposite P.RGO-MoS2, with a P.RGO-MoS2 ratio of 1:5. The P.RGO-MoSe2 (1:5) and P.BCN-MoS2 (1:5) nanocomposites exhibit somewhat lower activities of 9540 and 8593 μmol h–1 g–1, respectively. Prompted by literature reports that carbon-rich BCNs are efficient HER electrocatalysts, we have examined the electrocatalytic HER activity of P.BCN-MoS2 (1:1, 1:5, and 1:7) nanocomposites. The electrocatalytic HER activity of P.BCN-MoS2 (1:5) is found to be extraordinary, with an onset potential of −50 mV (vs RHE), comparable to that of platinum.

Solar driven thermal responsive polyionic liquid/PDDA semi-IPN hydrogel for near-room temperature membrane-free osmotic desalination

The designed thermally responsive polyionic liquid (TPIL)/ poly (diallyl dimethylammonium chloride) (PDDA) hydrogel with a semi-interpenetrating (semi-IPN) structure, containing highly charged chloride anions, was fabricated to explore the comprehensive capabilities of solar driven membrane-free osmotic desalination. Introducing linear PDDA polyelectrolyte with higher charge density has effectively excluded salt ions from entering the TPIL hydrogel matrix due to the strong charge concentration gradient established between the hydrogel and the saline reservoir. Meanwhile, the thermo-sensitivity of the polyionic liquid/PDDA semi-IPN (PNCl) hydrogel enabled the release of absorbed salt-depleted water at a temperature above the Lower Critical Solution Temperature (LCST). The multiple purification process established by partial submersion of PNCl hydrogel in saline enabled continual reduction of the salt ion concentration during the upwards transportation of water along the polyelectrolyte network. Moreover, a mushroom-shaped hydrogel demonstrated enhanced the effectiveness in long-term cyclic desalination. The “mushroom cap” was loaded with photo-thermal conversion fillers (Ti3C2Tx MXene) to achieve higher photo-thermal conversion efficiency for water recovery. A record high salt rejection rate of more than 93% was obtained for membrane-free osmotic desalination. More importantly the whole desalination/water absorption/release process was solely supported by gently heating the PNCl hydrogel under the illumination of renewable solar energy.

Fabrication and Characterization of Zein/PDADMAC Nanoparticles to Encapsulate Tebuconazole by Antisolvent Precipitation Method**

AbstractIn order to improve the sustained release effect and antifungal activity of tebuconazole (TEB), zein /poly dimethyl diallyl ammonium chloride (PDADMAC) nanoparticles (NPs) were prepared in this study. The hollow zein NPs were made by anti‐solvent precipitation method in which sodium carbonate was chosen as sacrificial template, and PDADMAC was combined with zein NPs via electrostatic self‐assembly after loading TEB. The NPs were characterized through particle size, Zeta potential, scanning electron microscopy (SEM), sustained release effect, contact angle, encapsulation efficiency (EE), loading efficiency (LE) and antifungal activity. In this study, TEB/zein/PDADMAC NPs were stable for at least 28 days at room temperature. The release of TEB showed lower release in NPs compared with technical concentrate (TEB TC, 98 %). In addition, NPs also significantly influenced performance such as wetting performance and antifungal activity. The developed functional TEB/zein/PDADMAC NPs with excellent properties can be promising for antifungal pesticide applications.

Detection of emerging disinfection by-products by reversed-phase ion-pair chromatography electrospray-ionization mass spectrometry in drinking water

A sensitive and specific methodology that allows unequivocal identification of polydiallyldimethylammonium chloride (PDADMAC) disinfection by-product it monomer diallyldimethylammonium chloride (DADMAC) in drinking water samples based on reversed-phase ion-pair chromatography–electrospray ionization – mass spectrometry was optimized. Ion-pair reagent heptafluorobutyric (HFBA) was found to play a crucial role in the optimization of chromatographic parameters. The chromatographic retention time was optimized by varying concentrations of ion-pair reagent, flow rate, and column temperature to enable good chromatographic retention and sensitivity of disinfection by-product of interest DADMAC in positive electrospray ionization and using selected ion monitoring (SIM) mode. The method was validated and showed good linear regression of 0.99 and a detection limit of 0.008 mg L−1. The developed method was applied in a drinking water treatment plant operated by Mgeni Water in Durban, South Africa, to detect trace levels of the disinfection by-product of interest (DADMAC) at various points of the treatment process. The concentration of DADMAC in the water treatment plant ranged from not detected up to 0.65 mg L−1. In addition, this work through mass spectrometry provides the first evidence of ion-pairing (465 m/z peak) between DADMAC and the reagent, which is a confirmation of online derivatization. Also, the use of ion-pair prevented dimerization of DADMAC (286 m/z peak) inside the ionization chamber leading to high sensitivity.

Synergistic enhancement of coal slurry water sedimentation and dehydration process using PDMDAAC/PAM

Currently, most coal processing plants use a single pharmaceutical system with large dosage and poor sedimentation effect, resulting in poor subsequent dehydration effect. In this study, poly dimethyl diallyl ammonium chloride (PDMDAAC) as coagulant, and polyacrylamide (PAM) as flocculant, were used for synergistic enhancement of the coal slurry water sedimentation and dehydration process. The best pharmaceutical system was determined by integrating the evaluation indexes in the sedimentation and dehydration process. The mechanism of synergistic enhancement of coal slurry water sedimentation and dehydration process using PDMDAAC/PAM was revealed by analyzing zeta potential, SEM, XPS and FTIR spectroscopy results. Moreover, the Box–Behnken response surface methodology was used to determine the order of significance of coagulant dosage (Cc), flocculant dosage (Cm), and coal slurry water concentration (Cs) on the combined sedimentation and dehydration indexes, and Cm > Cs > Cc. Further, the correlation models between the combined sedimentation and dehydration indexes and each factor were established, the pharmaceutical system was further optimized, and model accuracy was verified. The optimal dosage of PDMDAAC10040 was 2.96 mg/L, and that of PAM2610 was 2.31 mg/L. Then, the industrial trials were conducted at the Tara Trench coal processing plant. Interestingly, after replacing the chemical regime, the efficiency of the thickener and filter press has been significantly improved, resulting in a 33.33% reduction in cost. This research can provide significant theoretical guidance and technical support for industrial applications.

Enhanced separation and antifouling performance of ultrafiltration for surface water based on coagulation pretreatment by zirconium salts

Membrane fouling is the main challenge that limits ultrafiltration (UF) membrane long-term application. Coagulation, as an effective pretreatment method, not only reduces the pollutants loaded on the membrane surface, but also transforms membrane-pollutant contact into pollutant-floc reaction. Zircon (Zr) salts have drawn wide attention as a novel metal-based coagulant because of their excellent coagulation performance. In present study, three types of Zr coagulants zirconium tetrachloride (ZrCl4) and polyzirconium chloride (PZC), polyzirconium chloride/Poly dimethyl diallyl ammonium chloride (PZC/PDMDAAC) were estimated in terms of the coagulation removal of organic pollutants and the mitigation of membrane fouling. Results showed that the combination of PZC with alkalinity of 1.5 and PDMDAAC with molecular weight of 2.0–3.5 × 105 (abbreviated as PZC1.5/P2) presented the best coagulation performance under acidic and neutral conditions due to its better bridging affinity and sweeping ability. 8 mg/L dosage of PZC1.5/P2 could effectively remove turbidity (98.27%) and dissolved organic carbon (DOC) (59.04%) during the coagulation process. Furthermore, pre-coagulation by PZC1.5/P2 induced the transformation from cake filtration into thoroughly intermediate blocking and the removal of particulate matter would prevent reversible fouling-induced flux decline, whereas elimination of organic matter was beneficial for promoting UF efficiency by mitigating irreversible fouling. Besides, Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis showed that the foulants became more hydrophilic coagulated by PZC1.5/P2, and the adhesion between foulants and membrane surface was greatly weakened. All the improvement originated from the flocs structure contributed to the better UF performance with the improved normalize flux (J/J0) from 0.50 to 0.75, larger decrease in reversible and irreversible fouling by 82.27% and 91.27%, respectively. More importantly, PZC1.5/P2 exhibited excellent coagulation and membrane performances in the treatment of actual water from Wolf Mushan reservoir, which demonstrated that Zr-based coagulant is a promising coagulant for practical application in surface water purification.

PDDA coating method on surface of catalyst to form carbon shell for enhancing durability of polymer electrolyte membrane fuel cells

Construction of a physical protective layer on the catalyst surface of platinum-based catalysts in fuel cells to increase their durability has attracted attention of researchers. In particular, the carbon shell is suitable as a coating material because it covers relatively few active sites of Pt compared to other coating materials. However, the conventional carbon shell formation method is complex, time-consuming, and does not form a uniform layer easily. In this study, a new method for attaching a poly(diallyldimethylammonium chloride)(PDDA) polymer to the catalyst surface and forming a carbon shell through heat treatment was proposed. This method can easily forms a thin and uniform carbon shell with a thickness of ≤1 nm, minimizes performance reduction, and maintains superior durability of catalyst. For the 120-h single cell durability test, the current density at 0.6 V and maximum power density of Pt/C without carbon shell decreased by 32.3 % and 26.5 %, respectively, compared to the initial performance, whereas it was confirmed that 5.9 % and 9.0 % were reduced, respectively, in the case of carbon-shelled Pt/C manufactured in this study. This new method of carbon shell formation is expected to be easily applicable to various nanoparticle-based catalysts that require a physical protective layer to ensure durability.