Quaternary Ammonium Salt Groups Research Articles

Fabrication of dual functional marine antifouling coatings by infusing epoxy silicone oil modification of quaternary ammonium

Slippery liquid-infused porous surface (SLIPS) has attracted widespread attention in marine antifouling field, but it lacks the contact-killing ability, which limits its long-term anti-fouling efficiency. Herein, a SLIPS endowed with both resist and contact-killing antimicrobial performances is reported. Firstly, anodic aluminum oxides (AAO) with composite structures of the pores and pyramids were prepared and modified with siloxane. Then, a silicone oil containing quaternary ammonium salt (QAS-SO) groups was synthesized and infused into specially designed AAO, forming a QAS-SLIPS. The surface demonstrated remarkably anti-bacterial performances both Gram-positive Bacillus sp. and Gram-negative V. natriegens, and also maintained essential contact-killing antimicrobial activities from the grafted QAS groups. Biofouling testing suggested excellent antifouling performances of the QAS-SLIPS by declining the adhesion of 90.6 % Phaeodactylum tricornutum and 74.1 % of Chlorella pyrenoidosa. Overall, the antifouling performance of QAS-SLIPS comes primarily from two aspects, including physical isolation and contact-killing. Due to the easy of synthesis and excellent broad-spectrum antifouling effects, the QAS-SO could be potentially used for the development of antifouling coatings or as a lubricant for other devices.

Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration.

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447nm, branched fiber of 24.7nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4Pa) and a quality factor up to 0.083 Pa-1 on a 40µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.

Dynamic Antimicrobial Poly(disulfide) Coatings Exfoliate Biofilms On Demand Via Triggered Depolymerization.

Bacterial biofilms are notoriously problematic in applications ranging from biomedical implants to ship hulls. Cationic, amphiphilic antibacterial surface coatings delay the onset of biofilm formation by killing microbes on contact, but they lose effectiveness over time due to non-specific binding of biomass and biofilm formation. Harsh treatment methods are required to forcibly expel the biomass and regenerate a clean surface. Here, a simple, dynamically reversible method of polymer surface coating that enables both chemical killing on contact, and on-demand mechanical delamination of surface-bound biofilms, by triggered depolymerization of the underlying antimicrobial coating layer, is developed. Antimicrobial polymer derivatives based on α-lipoic acid (LA) undergo dynamic and reversible polymerization into polydisulfides functionalized with biocidal quaternary ammonium salt groups. These coatings kill >99.9% of Staphylococcus aureus cells, repeatedly for 15 cycles without loss of activity, for moderate microbial challenges (≈105 colony-forming units (CFU) mL-1, 1 h), but they ultimately foul under intense challenges (≈107 CFU mL-1, 5 days). The attached biofilms are then exfoliated from the polymer surface by UV-triggered degradation in an aqueous solution at neutral pH. This work provides a simple strategy for antimicrobial coatings that can kill bacteria on contact for extended timescales, followed by triggered biofilm removal under mild conditions.

Harnessing Renewable Lignocellulosic Potential for Sustainable Wastewater Purification.

Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development. However, the resulting by-products and the synthetic process characterized by complexity, high cost, and environmental pollution limit the further development of lignocellulose-based materials. Here, we developed a sustainable strategy that involved a new functional deep eutectic solvent (DES) to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups, lignin with carboxyl and quaternary ammonium salt groups, and DES effluent rich in lignin fragments. Subsequently, these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners, namely, photocatalyst prepared by carboxyl-modified cellulose residue, biochar-based adsorbent originated from modified lignin, and flocculant synthesized by self-catalytic insitu copolymerization of residual DES effluent at room temperature. Under the no-waste principle, this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality. These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water, including the removal of 99.81% of suspended solids, almost all various heavy metal ions, and 97.09% chemical oxygen demand, respectively. This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.

Quaternized chitosan/oxidized bacterial cellulose cryogels with shape recovery for noncompressible hemorrhage and wound healing

Management of noncompressible torso hemorrhage is an urgent clinical requirement, desiring biomaterials with rapid hemostasis, anti-infection and excellent resilient properties. In this research, we have prepared a highly resilient cryogel with both hemostatic and antibacterial effects by chemical crosslinking and electrostatic interaction. The network structure crosslinked by quaternized chitosan and genipin was interspersed with oxidized bacterial cellulose after lyophilization. The as-prepared cryogel can quickly return to the original volume when soaking in water or blood. The appropriately sized pores in the cryogel help to absorb blood cells and further activate coagulation, while the quaternary ammonium salt groups on quaternized chitosan inhibit bacterial infections. Both cell and animal experiments showed that the cryogel was hypotoxic and could promote the regeneration of wound tissue. This research provides a new pathway for the preparation of double crosslinking cryogels and offers effective and safe biomaterials for the emergent bleeding management of incompressible wounds.

A quaternary ammonium salt grafted tannin-based flocculant boosts the conjugative transfer of plasmid-born antibiotic resistance genes: The nonnegligible side of their flocculation-sterilization properties

This study developed dual-function tannin-based flocculants, namely tannin-graft-acrylamide-diallyl dimethyl ammonium chloride (TGCC-A/TGCC-C), endowed with enhanced flocculation-sterilization properties. The impacts of these flocculants on proliferation and transformation of antibiotic resistance genes (ARGs) among bacteria during the flocculation-deposition process were examined. TGCC-A/TGCC-C exhibited remarkable flocculation capacities towards both Escherichia coli and Staphylococcus aureus, encompassing a logarithmic range of initial cell density (108–109 CFU/mL) and a broad pH spectrum (pH 2–11). The grafted quaternary ammonium salt groups played pivotal parts in flocculation through charge neutralization and bridging mechanisms, concurrently contributing to sterilization by disrupting cellular membranes. The correlation between flocculation and sterilization entails a sequential progression, where an excess of TGCC, initially employed for flocculation, is subsequently consumed for sterilization purposes. The frequencies of ARGs conjugative transfer were enhanced in bacterial flocs across all TGCC treatments, stemming from augmented bacterial aggregation and cell membrane permeability, elicited stress response, and up-regulated genes encoding plasmid transfer. These findings underscore the indispensable role of flocculation-sterilization effects in mediating the propagation of ARGs, consequently providing substantial support for the scientific evaluation of the environmental risks associated with flocculants in the context of ARGs dissemination during the treatment of raw water featuring high bacterial density.

Locally Administered Photodynamic Therapy for Cancer Using Nano-Adhesive Photosensitizer.

Photodynamic therapy (PDT) is a great potential anti-tumor therapy owing to its non-invasiveness and high spatiotemporal selectivity. However, systemically administered photosensitizers diffuse in the skin and the eyes for a long duration, which cause phototoxicity to bright light and sunlight. Therefore, following PDT, patients must avoid exposure of to light and sunlight to avoid this phototoxicity. In this study, we have developed a locally administered PDT using nano-adhesive porphyrin with polycations consisting of quaternary ammonium salt groups (aHP) as a photosensitizer. The aHP, approximately 3.0 nm in diameter, adhered the negatively charged cell membrane via electrostatic interaction. The aHP localized to the endosome via cell adhesion and induced apoptosis upon 635 nm light irradiation. On being administered subcutaneously on the tumor, 30% of the injected aHP remained in the administered sites. However, low-molecular-weight hematoporphyrin dihydrochloride (HP) disappeared due to rapid diffusion. PDT with locally administered aHP showed a higher anti-tumor effect after light irradiation at 635 nm for three days compared to low-molecular-weight HP. Intraperitoneal administration of HP caused severe phototoxicity upon irradiation with ultraviolet A at 10 J cm-2, whereas aHP did not cause phototoxicity because its diffusion into the skin could be suppressed, probably due to the high-molecular weight of aHP. Therefore, locally administered PDT with aHP is a potential PDT having high therapeutic efficacy without phototoxicity.

Spatiotemporally Responsive Hydrogel Dressing with Self-Adaptive Antibacterial Activity and Cell Compatibility for Wound Sealing and Healing.

Adhesive hydrogels containing quaternary ammonium salt (QAS) moieties have shown attractive advantages in treatment for acute wounds, attributed to their high performances in wound sealing and sterilization. However, the introduction of QAS commonly leads to high cytotoxicity and adhesive deterioration. Herein, aimed to solve these two issues, a self-adaptive dressing with delicate spatiotemporal responsiveness is developed by employing cellulose sulfate (CS) as dynamic layers to coat QAS-based hydrogel. In detail, due to the acid environment of wound in the early stages of healing, the CS coating will quickly detach to expose the active QAS groups for maximum disinfectant efficacy; meanwhile, as the wound gradually heals and recovers to a neutral pH, the CS will remain stable to keep QAS screened, realizing a high cell growth-promoting activity for epithelium regeneration. Additionally, attributed to the synergy of temporary hydrophobicity by CS and slow water absorption kinetics of the hydrogel, the resultant dressing possesses outstanding wound sealing and hemostasis performance. At last, this work anticipates this approach to intelligent wound dressings based on dynamic and responsive intermolecular interaction can also be applied to a wide range of self-adaptive biomedical materials employing different chemistries for applications in medical therapy and health monitoring.

Biodegradable and Cytocompatible Hydrogel Coating with Antibacterial Activity for the Prevention of Implant-Associated Infection.

Implant-associated infection (IAI) caused by pathogens colonizing on the implant surface is a serious issue in the trauma-orthopedic surgery, which often leads to implant failure. The complications of IAI bring a big threat to the clinical practice of implants, accompanied by significant economic cost and long hospitalization time. In this study, we propose an antibiotics-free strategy to address IAI-related challenges by using a biodegradable and cytocompatible hydrogel coating. To achieve this, a novel hydrogel system was developed to combine the synergistic effects of good cell affinity and antibacterial properties. The hydrogel material was prepared by modifying a photocross-linkable gelatin-based polymer (GelMA) with cationic quaternary ammonium salt (QAS) groups via a mild and simple synthesis procedure. By engineering the length of the hydrophobic carbon chain on the QAS group and the degree of functionalization, the resulting GelMA-octylQAS hydrogel exhibited an integration of good mechanical properties, biodegradability, excellent bactericidal activity against various types of bacteria, and high cytocompatibility with mammalian cells. When coated onto the implant via the in situ cross-linking procedure, our hydrogel demonstrated superior antimicrobial ability in the infective model of femoral fracture of rats. Our results suggest that the GelMA-octylQAS hydrogel might provide a promising platform for preventing and treating IAI.

Cationic Pullulan Derivatives Based Flocculants for Removal of Some Metal Oxides from Simulated Wastewater

Modified polysaccharides have been increasingly used as flocculants in wastewater treatment due to their non-toxicity, low price, biodegradability, etc. However, the pullulan derivatives are less used in wastewater purification processes. Therefore, this article presents some data regarding FeO and TiO2 particle removal from model suspensions by some pullulan derivatives with pendant quaternary ammonium salt groups, trimethylammonium propyl carbamate chloride (TMAPx-P). The influence of the polymer ionic content, dose, and initial solution concentration as well as of the dispersion pH and composition (metal oxide content, salts, and kaolin) on the separation efficacy were considered. UV-Vis spectroscopy measurements have shown a very good removal efficacy of TMAPx-P for the FeO particles (around 95% and more), irrespective of the polymer and suspension characteristics; a lower clarification of the TiO2 particles suspension (removal efficiency between 68% and 75%) was noticed. Both the zeta potential and the particle aggregates size measurements revealed the charge patch as the main mechanism which governs the metal oxide removal process. The surface morphology analysis/EDX data provided supplementary evidence regarding the separation process. A good removal efficiency (90%) of the pullulan derivatives/FeO flocs for the Bordeaux mixture particles from simulated wastewater was found.

Cationic Conjugated Microporous Polymers Coating for Dual‐Modal Antimicrobial Inactivation with Self‐Sterilization and Reusability Functions

AbstractCOVID‐19 pandemic outbreak poses a great threat to human health. Face masks have been considered as important personal protective equipment to prevent the COVID‐19 transmission. However, pathogens can survive up to several days on the fabrics of commercial masks, which increases the risk of direct/indirect microbial transmission. Herein, new cationic conjugated microporous polymers (CCMPs)‐based coating is developed, which possesses extended π‐conjugated skeletons and massive quaternary ammonium salt (QAS) groups, exhibiting dual‐modal antimicrobial inactivation, including sunlight‐driven photodynamic sterilization through the generation of reactive oxygen species and contact sterilization through QAS groups. As a result, the CCMPs coatings can rapidly and efficiently eradicate 99% of model microbes, such as Escherichia coli and Staphylococcus aureus under solar illumination, and also ensure the great antimicrobial effect in the absence of light. More importantly, the CCMPs coatings exhibit excellent durability, reusability as well as antimicrobial stability in humid environment. Contributing to the outstanding processability and formability, CCMPs can be in situ synthesized and coated over fibers through a simple spray procedure. Taken together, the design provides a promising strategy for developing reusable and self‐sterilizing antimicrobial fabrics, particularly for the application of face masks to tackle infectious pathogen and viruses in daily protection and medical applications.

Anti-biofouling property and anti-leaching investigation of modifier for PVDF ultrafiltration membrane by incorporating antibacterial graphene oxide derivatives

To improve the anti-biofouling property of polyvinylidene fluoride (PVDF) membrane, three kinds of antibacterial graphene oxide (GO) derivatives were prepared, including imidazole-functionalized GO (Im-GO) and quaternized GO (Q-GO) synthesized by chemical grafting method, and GO loaded with silver nanoparticles (GO-Ag) synthesized by in-site reduction method. The structural characteristics and antibacterial abilities of three kinds of GO derivatives were characterized and investigated. It was demonstrated that GO could be used as a good carrier to prepare the anti-biofouling modifiers. Correspondingly, Im-GO/PVDF, Q-GO/PVDF, and GO-Ag/PVDF ultrafiltration membranes were fabricated using the phase inversion method. In contrast with the blank PVDF membrane, all the GO derivatives/PVDF membranes showed greatly improved permeability and anti-biofouling property. Significantly, the inhibition zone test and fluorescence staining experiment were carried out to investigate the differences between Im-GO, Q-GO, and GO-Ag in the antibacterial mechanisms. The corresponding results suggest that the imidazole and quaternary ammonium salt groups grafted on Im-GO and Q-GO possess great anti-leaching characteristics, while the loss of Ag+ from GO-Ag is relatively obvious. Therefore, Im-GO and Q-GO synthesized by chemical grafting method have greater potential as the anti-biofouling membrane modifiers, considering the accumulation of harmful ions in water and possible reduction in antibacterial stability for GO-Ag.

Improvement of Antibacterial and Antifouling Properties of a Cellulose Acetate Membrane by Surface Grafting Quaternary Ammonium Salt.

Through etherification reaction, epoxy propyl dimethyl dodecyl ammonium chloride (EPDMDAC) was grafted onto the surface of a cellulose acetate (CA) membrane to prepare a stable nonleaching antibacterial antifouling membrane (QCA-X). The results showed that with the extension of grafting reaction time, the quaternary ammonium salt groups on the membrane surface increased and the hydrophilicity was enhanced. Compared with those of the CA membrane, the filtration capacity and antifouling performance of the QCA-X membrane are improved. When the grafting time is 4 h, the water permeability and flux recovery rate of the QCA-4 membrane are increased by 139 and 21.5%, respectively. The QCA-X membrane showed excellent antibacterial performance, and the sterilization rate against S. aureus and E. coli was more than 99.99%. After four repeated antibacterial cycles, the bactericidal rates against S. aureus and E. coli were maintained at about 99.69 ± 0.02 and 99.98 ± 0.02%, respectively, with good antibacterial persistence. Moreover, the QCA-X membrane can effectively inhibit bacterial adhesion. Mild and simple EPDMDAC grafting modifications improve the antibacterial, antifouling, and antibioadhesion properties of the CA membrane, showing its application potential in long-term water treatment, especially in biofouling water treatment.

Ionic aqueous quaternized Poly(amide-imide) sizing on CF for improving interface and mechanical performance of CFRTP

With the rapid development of automotive, aviation, and aerospace, Carbon fiber reinforced thermoplastic polymer (CFRTP) has been widely used. However, massive commercial surfactants were used in present aqueous sizings for CF in high-performance CFRTP since thermoplastic polymers in sizing were all hydrophobic, which resulted in thermal instability and mechanical performance decrease. To solve this problem, herein, quaternary ammonium salt groups were introduced to poly (amide-imide)(PAI) via click-reaction, a novel quaternized PAI with excellent solubility and thermal stability was synthesized. An aqueous thermoplastic CF sizing was prepared via self-emulsifying of quaternized PAI without surfactants for the first time, which was stable after 12-month-storage. Furthermore, PAI-sized CF with appropriate processability was obtained for the manufacture of CF/PEI (polyether-imide) and CF/PEEK (polyether-ether-ketone) composites. Mechanical performances and hydrothermal aging resistance of composites were all significantly improved. Especially, quantum chemical calculations were employed to reveal the mechanisms of interface strengthening in composites, there were hydrogen bonding and π-π stacking between PAI sizing and PEI, PEEK matrix.

Engineering DNA-Guided Hydroxyapatite Bulk Materials with High Stiffness and Outstanding Antimicrobial Ability for Dental Inlay Applications.

Programmable base pair interactions at the nanoscale make DNA an attractive scaffold for forming hydroxyapatite (HAP) nanostructures. However, engineering macroscale HAP mineralization guided by DNA molecules remains challenging. To overcome this issue, a facile strategy is developed for the fabrication of ultrastiff DNA-HAP bulk composites. The electrostatic complexation of DNA and a surfactant with a quaternary ammonium salt group enables the formation of long-range ordered scaffolds using electrospinning. The growth of 1D and 2D HAP minerals is thus realized by this DNA template at a macroscale. Remarkably, the as-prepared DNA-HAP composites exhibit an ultrahigh Young's modulus of ≈25GPa, which is comparable to natural HAP and superior to most artificial mineralized composites. Furthermore, anew type of dental inlay with outstanding antibacterial properties is developed using the stiff DNA-HAP. The encapsulated quaternary ammonium group within the dense HAP endows the composite with long-lasting and local antibacterial activity. Therefore, this new type of super-stiff biomaterial holds great potential for oral prosthetic applications.

Long-Term Fluorescent Tissue Marking Using Tissue-Adhesive Porphyrin with Polycations Consisting of Quaternary Ammonium Salt Groups.

Localization of tumors during laparoscopic surgery is generally performed by locally injecting India ink into the submucosal layer of the gastrointestinal tract using endoscopy. However, the location of the tumor is obscured because of the black-stained surgical field and the blurring caused by India ink. To solve this problem, in this study, we developed a tissue-adhesive porphyrin with polycations consisting of quaternary ammonium salt groups. To evaluate the ability of tissue-adhesive porphyrin in vivo, low-molecular-weight hematoporphyrin and tissue-adhesive porphyrin were injected into the anterior wall of the exposed stomach in rats. Local injection of low-molecular-weight hematoporphyrin into the anterior wall of the stomach was not visible even after 1 day because of its rapid diffusion. In contrast, the red fluorescence of the tissue-adhesive porphyrin was visible even after 7 days due to the electrostatic interactions between the positively-charged moieties of the polycation in the tissue-adhesive porphyrin and the negatively-charged molecules in the tissue. In addition, intraperitoneal injection of tissue-adhesive porphyrin in rats did not cause adverse effects such as weight loss, hepatic or renal dysfunction, or organ adhesion in the abdominal cavity. These results indicate that tissue-adhesive porphyrin is a promising fluorescent tissue-marking agent.

Influence of cationic groups on the antibacterial behavior of cationic nano-sized hyperbranched polymers to enhance bacteria-infected wound healing.

With the continuous emergence of drug-resistant pathogens, new strategies with high antibacterial efficacy are urgently needed. Herein, five cationic nano-sized hyperbranched polymers (CNHBPs) with cationic functional groups have been constructed, and their antibacterial mechanism has been studied in detail. CNHBPs bearing secondary ammonium salt groups and long alkyl chains (S12-CNHBP) exhibited weak antibacterial and antibiofilm ability, while CNHBPs bearing quaternary ammonium salt groups and long alkyl chains (Q12-CNHBP) showed the highest antimicrobial and strongest antibiofilm activities. ζ potential and isothermal titration microcalorimetry (ITC) results suggest that the negatively charged surfaces of bacterial cells provided Q12-CNHBP with a higher intrinsic electrostatic driving force for bacterial killing than that with S12-CNHBP. Fluorescent tracing and morphological observations indicate that the bacterial genome might be another antibacterial target for S12-CNHBP in addition to the cell wall and membrane, which are mainly antibacterial targets for Q12-CNHBP, making it less likely to induce bacterial resistance. Surprisingly, Q12-CNHBP exhibited superior in vivo therapeutic efficacy in a mouse wound model of methicillin-resistant Staphylococcus aureus (MRSA) infection with low toxicity during treatment. These advantages and ease of preparation will undoubtedly distinguish Q12-CNHBP as a new class of suitable candidates to combat multidrug-resistant pathogen infections. This study opens up a new avenue for exploiting antibacterial biomaterials to treat infections caused by drug-resistant bacteria.

Peptidoglycan-inspired peptide-modified injectable hydrogels with enhanced elimination capability of bacterial biofilm for chronic wound healing

Majority of human infectious diseases is related to bacterial biofilm formation, especially the wound infection and delayed healing. Herein, recognizing peptide-modified polysaccharide based injectable hydrogel has been synthesized for effective anti-biofilm and infected wound healing. Inspiration from similar compatibility principle, the peptide (Alanine-glutamate-lysine-alanine), which is a part of the peptidoglycan, is grafted into the quaternized carboxymethyl chitosan （HTCC）for the first time. Afterwards, the quaternary ammonium salt groups in the synthetic injectable hydrogel cross-linked by the peptide modified quaternized carboxymethyl chitosan (HTCC-P) and oxidized dextran (OD), which can penetrate the bacterial cell wall and membrane under the recognition of peptide. Furthermore, the synergistic effect of quaternary ammonium salt groups and the peptide significantly enhance the anti-biofilm property of the hydrogels. In addition, the injectable hydrogel (HTCC-P/OD) cross-linked by Schiff base exhibits an excellent self-healing property and can completely cover the irregular wound shape. The cytotoxicity and in vivo wound healing also confirm the biocompatibility and capacity to accelerate tissue reconstruction of the hydrogels. Therefore, the hydrogels are expected to become competitive multifunctional dressings in biomedical field, including chronic wound infection and other bacterial biofilm related tissue repair.

The separation of kreutzonit particles by cationic pullulan derivatives from model suspension

In the present work the flocculation properties of some cationic derivatives based on pullulan have been tested in a synthetic suspension of zirconium silicate (kreutzonit). The flocculants contain either quaternary ammonium salt groups (grafted chains, poly[(3-acrylamidopropyl)-trimethylammonium chloride] onto the pullulan (P-g-pAPTAC)) or tertiary amine groups (3-dimethylamino-1-propylamine-pullulan) (DMAPAX-P). The impact of polymer dose, the charge content and type (tertiary amine or quaternary ammonium salt groups), the grafted chains length and the suspension pH on the flocculation efficiency have been taken into consideration. The separation of mixtures consisting of kreutzonit, K-feldspar, kaolin, hematite (Fe2O3) particles by some of the above mentioned cationic derivatives was also followed. The addition of different doses of pullulan derivatives to kreutzonit dispersion as well as to particles mixture led to the increase of particles removal efficiency up to 95–99% in the optimum dose intervals. The charge patch and bridging mechanisms played an important role in the flocculation process, as revealed by zeta potential measurements. Flocs resulting from the flocculation process have been used successfully in removal of fungicide Bordeaux mixture particles from synthetic wastewater; a removal efficiency higher than 95% has been found for the optimum amount of flocs (10 g flocs per liter of fungicide suspension).

Impacts of degree of substitution of quaternary cellulose on the strength improvement of fiber networks

The degree of substitution (DS) of cellulose derivative is significantly associated with its properties. In this paper, a series of quaternary cellulose (QC) samples with different DS (ranging from 0.16 to 0.51) were synthesized with assistance of microwave and their relationship with strength improvement of fiber networks was investigated systematically. QCs were characterized by elemental analysis, FT-IR, 1H NMR, and TGA, etc. The results showed that the cationic quaternary ammonium salt group was successfully grafted onto the backbones of cellulose chains and the thermal stability was associated inversely with the DS of QCs. However, the results of strength test for the fiber networks from secondary fiber of old corrugated containers showed that the tensile and burst strength was enhanced by addition of QCs, and their performance was positively correlated their DS. The best result achieved in this investigation was in the case of QC with DS of 0.51, with increments of tensile and burst strength 6.17% and 11.68%, respectively, at a dosage of 1.0 wt% based on oven-dry pulp. This investigation highlights the importance of DS of QC to its application in strength improvement for fiber networks.