Electrostatic Complexation Research Articles

Adsorption Performance and Mechanism of H3PO4-Modified Banana Peel Hydrothermal Carbon on Pb(II)

This study investigated the adsorption performance of hydrothermal carbon derived from banana peel and modified with different concentrations of phosphoric acid solution, then used to adsorb lead ions in an aqueous solution. The surface structure and functional groups of the modified hydrothermal carbon were analyzed using XRD, SEM, FT-IR, elemental analysis, and BET. The results showed that the adsorption capacity of modified hydrothermal carbon derived from banana peel reached 40.64 mg/g at a hydrothermal temperature of 240 °C, a phosphoric acid solution of 2 mol/L, and a solid–liquid ratio of 2 g/L, with a removal efficiency of 82.74%. The adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm equation. The correlation coefficient of 0.99 for fitting the adsorption process using an artificial neural network, indicating that the artificial neural network could be used to predict adsorption. The adsorption of Pb(II) from an aqueous solution by phosphoric acid-modified hydrothermal carbon was dominated by monolayer chemical adsorption, and the adsorption mechanisms included electrostatic attraction, ion exchange, surface complexation, and physical adsorption.

Facile synthesis of δ-MnO2 biotemplated by waste tobacco stem-silks for enhanced removal of Sb(III).

The elimination of antimony pollution has attracted increasing concerns because of its high toxicity to human health and the natural environment. In this work, biomimetic δ-MnO2 was synthesized by using waste tobacco stem-silks as biotemplate (Bio-δ-MnO2) and used in the capture of Sb(III)from aqueous solution. The tobacco stem-silks not only provided unique wrinkled morphologies but also contained carbon element self-doped into the resulting samples. The maximum Sb(III) adsorption capacity reached 763.4mg∙g -1, which is 2.06 times higher than δ-MnO2 without template (370.0mg∙g -1), 4.53 times than tobacco stem-silks carbon (168.5mg∙g -1), and 10.39 times than commercial MnO2 (73.5mg∙g -1), respectively. The isotherm and kinetic studies indicated that the adsorption behavior was consistent with the Langmuir isotherm model and the pseudo-second-order kinetic equation. As far as we are aware, the adsorption capacity of Bio-δ-MnO2 is much higher than that of most Sb(III) adsorbents. FT-IR, XPS, SEM, XRD, and Zeta potential analyses showed that the main mechanism for the adsorption of Sb(III) by Bio-δ-MnO2 includes electrostatic attraction, surface complexation, and redox. Overall, this study provides a new sustainable way to convert agricultural wastes to more valuable products such as biomimetic adsorbent for Sb(III) removal in addition to conventional activated carbon and biochar.

Co-adsorption of tetracycline and copper by the thiourea-modified porous sodium alginate microspheres

The gradual increase of antibiotics and heavy metals in aquatic environments poses a serious threat to human health and ecosystems, and finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concern. In this study, a novel porous structure of thiourea-modified sodium alginate microspheres (UA-Ca) was synthesized by modification with thiourea, epichlorohydrin, and calcium chloride, and was applied for the simultaneous removal of tetracycline (TC) and Cu(II) from water. The results indicated that the UA-Ca material with 1:2 mass ratio of thiourea and sodium alginate showed the highest removal of TC and Cu(II) under the reaction condition of pH= 7. The removal process of both TC and Cu(II) follows the pseudo-second-order adsorption model and Langmuir isotherm model. UA-Ca had a high adsorption capacity toward TC and Cu(II) with the maximum value of 1.099 mmol/g and 2.793 mmol/g based on the Langmuir model at 298 K, respectively. Thermodynamical parameters revealed that TC and Cu(II) adsorption is spontaneous with endothermic nature. Competing ionic cations (Ca2+、Mg2+、NH4+) and organics (sulfamethoxazole, hygromycin) had a certain inhibitory effect on the removal of TC and Cu(II) by UA-Ca, whereas the anionic ions (CO32-、PO43-、SO42-) all had little effect on its removal. Fourier transform infrared spectra and X-ray photoelectron spectroscopy analyses showed that the removal of TC and Cu(II) by UA-Ca was mainly due to electrostatic adsorption and surface complexation. This work provides a promising UA-Ca material for the effective removal of TC and Cu(II) in contaminated water.

Cu(II) inhibited the transport of tetracycline in porous media: role of complexation.

Tetracycline (TC) and Cu(II) coexist commonly in various waters, which may infiltrate into the subterranean environment through runoff and leaching, resulting in substantial ecological risks. However, the underlying mechanisms why Cu(II) affects the transport of TC in porous media remain to be further explored and supported by more evidence, especially the role of complexation. In this study, the transport of TC with coexisting Cu(II) was comprehensively explored with column experiments and density functional theory (DFT) calculation. At natural environmental concentrations, Cu(II) significantly inhibited the transport of TC in the quartz sand column. Cu(II) augmented the retention of TC in the column mainly via electrostatic force and complexation. The interaction between TC and TC-Cu complexes on the surface of SiO2 was investigated with first-principles calculations for the first time. There were strong van der Waals forces and coordination bonds on the surface of complexes and SiO2, leading to higher adsorption energy than that of TC and inhibiting its penetration. This study offers novel insights and theoretical framework for the transport of antibiotics in the presence of metal ions to better understand the fate of antibiotics in nature.

The preparation of spherical Dopamine/Carbon for the efficient removal of uranium

As Japan releases nuclear wastewater into the ocean, radioactive contamination has caused global concern. Among those radioactive contaminants, uranium(U) is one of the worst pollutants. This study prepares the spherical dopamine/carbon(DA/C) through a simple hydrothermal process to remove U(VI) from water. In adsorption, uranium ions are adsorbed on the material surface and gradually enter the material through the pores. U(VI) adsorption is a single molecule adsorption process, and the adsorption capacity of the DA/C is 30.4 mg/g at pH = 7.0 and 288 K. U(VI) adsorption depends on electrostatic attraction and complexation. The hydroxyl groups and amino groups of the DA/C can form complexes with U(VI) ions. The DA/C possesses excellent desorption and regeneration ability, which can be used for U(VI) removal and extract uranium from seawater. This study provides a new idea for enriching U(VI), which helps control radioactive pollution.

Novel modified semi-carbonized fiber prepared using discarded clothes for derisking Cu(II) and Pb(II) contaminated water

We report a novel modified semi-carbonized fiber (CF) prepared using cotton and acrylic clothes for derisking contaminated water to realize the resource utilization of discarded clothes in wastewater treatment. In this study, amphoteric and auxiliary modifiers were used to modify CFs for preparing amphoteric and amphoteric-auxiliary CFs. The basic physicochemical properties of different modified CFs were determined, and the microscopic morphology of modified CFs was detected. The isothermal adsorption characteristics of Cu(II) and Pb(II) on different modified CFs were investigated by the batch method, and the effect mechanisms of temperature, pH, ionic strength, and material dose were compared. Physicochemical properties and microscopic morphology results proved that amphoteric and auxiliary modifiers were modified on the CF surface and changed the surface properties of CF. The adsorption capacities of Cu(II) and Pb(II) on modified CFs increased with the increase in equilibrium concentration of Cu(II) and Pb(II), and the isotherm was more suitable for Freundlich model fitting than that of the Langmuir model. The maximum adsorption capacities (qm) of Cu(II) and Pb(II) on different modified CFs were 60.72–81.26 mg/g and 102.58–161.72 mg/g, respectively, and presented the trend of amphoteric-auxiliary CFs > amphoteric CFs > CFs. Increasing pH and temperature and decreasing ionic strength and material dose were beneficial to Cu(II) and Pb(II) adsorption. The Cu(II) and Pb(II) adsorption process was a spontaneous, endothermic, and entropy-increasing reaction, and the adsorption rate was controlled by chemisorption. The adsorption amount of amphoteric-auxiliary CFs maintained about 65% of original materials after 3 times of regeneration. Electrostatic attraction, precipitation, complexation, and ion exchange were the main adsorption mechanisms. The cation exchange capacity and total pore volume of modified CFs were key to determining qm of Cu(II) and Pb(II).

Fabrication of poly(β-amino ester) and hyaluronic acid based pH responsive nanocomplex as an antibiotic release system

World Health Organization (WHO) warns about antimicrobial resistance (AMR) considered as the most serious threats to global health, food security, and development. There are various efforts for elimination of this serious issue. These efforts include education of individuals, new policies, development of new antimicrobials and new materials for effective delivery. Novel drug delivery systems with ability of local and on-demand delivery are one of the promising approaches for prevention of AMR. In this regard, a pH-responsive antibiotic delivery system based on pH-responsive poly(β-amino ester) (PBAE) and enzyme responsive hyaluronic acid (HA). The polymeric nanocomplexes were obtained via electrostatic complexation of PBAE and HA in the presence of a model antibiotics, colistin and vancomycin. The particle sizes at pH 7.4 were determined in the range of 131–730 nm and 120–400 nm by DLS and STEM, respectively. When pH was switched from 7.4 to 5.5, the hydrodynamic diameter increased 2.5–32 fold. The drug release performances were tested using FITC-labeled antibiotics via fluorescence spectroscopy. The nanocomplexes released the drugs more at pH 5.5 compared to pH 7.4. Antibacterial activity of the system was evaluated on various bacteria. The nanocomplex loaded with the antibiotics exhibited significantly greater efficacy against E. coli and S. aureus.

A convenient functionalization strategy of polyimide covalent organic frameworks for uranium-containing wastewater treatment and uranium recovery

The purpose of this research was to design and synthesize an adsorbent based on polyimide covalent organic frameworks (PICOFs) for uranium-containing wastewater treatment and uranium recovery. A modified solvothermal method was innovatively proposed to synthesize PICOFs with high specific surface area (1998.5 m2 g−1) and regular pore structure. Additionally, a convenient functionalization strategy of PICOFs was designed through polydopamine (PDA) and a well-dispersed polymer (MPC-co-AO) containing multiple functional groups, forming stable composite (PMCA-TPPICOFs) in which the hydrogen bonding and cation-π interactions between PDA and MPC-co-AO played a key role. The obtained PMCA-TPPICOFs as an adsorbent exhibited strong selectivity for uranyl ions (maximum adsorption capacity was 538 mg g−1). In simulated wastewater with low uranium concentrations, the removal rate reached 98.3%, and the concentration of treated simulated wastewater met discharge standards. Moreover, PMCA-TPPICOFs was suitable for fixed-bed column adsorption because of its favorable structure. According to the research about adsorption mechanism, the adsorption primarily relied on electrostatic interaction and complexation. In summary, PMCA-TPPICOFs exhibited good potential for uranium-containing wastewater treatment, expanding the application of PICOFs. And the proposed functionalization strategy and modified solvothermal method may promote research in the fields of material functionalization and COFs synthesis. Environmental ImplicationUranium is a raw material for nuclear energy applications, which is toxic and radioactive. If uranium is discharged with wastewater, it would not only pose a threat to the environmental protection and life safety, but also cause the loss of precious nuclear raw materials. Although adsorption was considered to be an effective way to remove uranium, many of the developed adsorbents were difficult to apply due to the harsh wastewater environment and complex preparation processes. This study reported a novel adsorbent and a new functionalization strategy, which was expected to solve the problem of uranium recovery in wastewater.

Fe3S4 intercalated alkalized MXenes to enhancement of Au(III) and Cr(VI) removal by reduction and immobilization synergistic effect

Herein, Fe3S4 particles were introduced into an alkalized-Nb2CTx MXenes to construct Fe3S4@Alk-Nb2CTx composite for simultaneous reduction-immobilization of Au(III)/Cr(VI) from water aqueous. Spectrum analysis revealed that the –OH groups on the Alk-Nb2CTx surface assisted improving the dispersion and stability of Fe3S4, resulting in a favorable morphology and structure. The synthesized composites exhibited superior adsorptive property with a maximum adsorption values for Au(III) (2544.3 mg/g) and Cr(VI) (204.8 mg/g). Meanwhile, the removal of targeted pollutants on Fe3S4@Alk-Nb2CTx followed Pseudo-second order kinetics model and showed a good fit with the Langmuir isotherm model, indicating the nature of monolayer chemisorption. Besides, high adsorption selectivity of Fe3S4@Alk-Nb2CTx was still observed in the presence of interference ions, and it could be separated conveniently from solution by a magnet. More importantly, the model-fitting and characterization results manifested that high-density Fe, S and O groups were the main active factors in the as-prepared adsorbents, while the electrostatic attraction, complexation, redox and precipitation dominated the adsorption process. Hence, Fe3S4@Alk-Nb2CTx was a promising candidate employed for in situ environmental pollution incidents, especially competent for the reduction and removal of Au(III)/Cr(VI).

The evaluation of mixed-layer emulsions stabilized by myofibrillar protein-chitosan complex for delivering astaxanthin: Fabrication, characterization, stability and in vitro digestibility

Muscle protein based functional foods have been attracted great interests in novel food designing. Herein, myofibrillar protein (MP)-chitosan (CH) electrostatic complexes were employed to fabricate mixed-layer emulsions to protect and deliver astaxanthin. The MP/CH complex fabricated mixed-layer emulsions displayed higher stability against pH and temperature changes, exhibiting smaller droplet and homogenous distributions. After UV-light irradiation for 8 h, the mixed-layer emulsions had higher astaxanthin retention (69.11 %, 1:1 group). During storage, a lower degree of lipid oxidation, protein oxidation and higher astaxanthin retention were obtained, indicating desirable protections of mixed-layer emulsions. The vitro digestion reveled the mixed-layer emulsions could decrease the release of free fatty acids. Meanwhile, the bioaccessibility of astaxanthin was higher (30.43 %, 2:1 group) than monolayer emulsion. In all, the MP/CH prepared mixed-layer emulsions could protect and deliver fat-soluble bioactive compounds, and contributed to develop muscle protein based functional foods to meet the needs of slow and controlled release.

Hexavalent chromium removal using reduced graphene oxide-zinc oxide composite fabricated via simple pyrolysis method

The contamination of water by heavy metals from various industrial effluents is a significant factor contributing to the scarcity of clean water worldwide. To address this issue, there is a need to develop low-cost adsorbents to remove heavy metals from contaminated water reduced graphene oxide (rGO) based composites are efficient adsorbers of heavy metals. In this study, a green and rapid single-step heating process was utilized to prepare both rGO and rGO/ZnO composite materials, avoiding the use of any toxic reagents. The rGO/ZnO composite synthesized from sucrose and zinc acetate demonstrates a remarkable ability to adsorb hexavalent chromium (Cr(VI)). The Cr adsorption studies were carried out by varying adsorbent, contact time, initial pH, and concentration. The adsorption efficiency of the composite is five times higher than that of pure rGO. The adsorption mechanism of Cr(VI) onto the adsorbent is electrostatic interaction, complexation, pore filling, and reduction, identified through Zeta potential measurement, BET, EDX, and XPS analysis. These studies suggest that rGO/ZnO composite has great potency as a cost-effective and efficient adsorbent for removing Cr(VI) contaminants from industrial effluents.

Adsorption Behavior of Organoarsenicals over MnFe2O4-Graphene Hybrid Nanocomposite: The Role of Organoarsenic Chemical Structures.

As a kind of emerging contaminant, organoarsenic compounds have drawn wide concern because of their considerable solubilities in water, and the highly toxic inorganic arsenic species formed during their biotic and abiotic degradation in the natural environment. Thus, the effective removal and studying of the adsorption mechanism of organoarsenic compounds are of significant urgency. In this work, MnFe2O4 and MnFe2O4/graphene were prepared through a facile solvothermal method. From the results of the Transmission Electron Microscope (TEM) characterization, it can be found that MnFe2O4 nanoparticles were uniformly distributed on the surface of the graphene. And the specific surface area of the MnFe2O4/graphene was about 146.39 m2 g-1, much higher than that of the MnFe2O4 (86.15 m2 g-1). The interactions between organoarsenic compounds and adsorbents were conducted to study their adsorption behavior and mechanism. The maximum adsorption capacities of MnFe2O4/graphene towards p-arsanilic acid (p-ASA) and roxarsone (ROX) were calculated to be 22.75 and 30.59 mg g-1. Additionally, the ionic strength, negative ions, and humus were introduced to investigate the adsorption performance of organoarsenic compounds. Electrostatic adsorption and surface complexation are the primary adsorption mechanisms on account of X-ray photoelectron spectroscopy (XPS) and the Fourier-transform infrared spectroscopy (FT-IR) analysis. This research extends the knowledge into studying the interaction between organoarsenic species and hybrid nanomaterials in the natural environment.

Insight into the humic acid/antibiotic complexation for boosting tetracycline degradation by heterogeneous persulfate activation

Little attention has been paid to the degradation of antibiotics in their bound states, although numerous ionizable organic micro-pollutants possessed a strong tendency towards complexing with natural organic matters (NOM) in aquatic ecosystems. This study systematically investigated the degradation kinetics of tetracycline (TCH) bound with humic acid (HA) versus free TCH in heterogeneous persulfate activation system. Contrary to the homogeneous UV/PS oxidation processes documented, the complexation with HA promoted the removal of TCH due to the adsorption behavior of TCH on the heterogeneous catalyst. The results displayed that higher first-order rate constants of HA-bound TCH degradation (up to 3.8 folds) were obtained compared to free TCH at varying TCH and HA concentrations. The presence of ionic strength, alkalinity and hardness had an inhibitory effect on the degradation of bound TCH, and the effect of pH was more significant due to the change of electrostatic complexation of TCH/HA. Differential absorbance spectra further identified that the degradation sensitivity followed the order of bound TCH ＞ free TCH in TCH/HA mixed systems. In addition, the enhanced interfacial electron transfer that played a dominant role in TCH oxidation may be responsible for the efficient removal of TCH in the bound state. Results of this study provide new insights into the NOM/antibiotics complexation for boosting the antibiotics degradation in heterogeneous catalysis.

Enhancing lead removal from wastewater and alleviating lead stress in soil-wheat systems using starch-stabilized Fe-Ni/biochar composites: Synthesis and physico-chemical investigations

In this study, starch-stabilized and Fe/Ni bimetal modified biochar composites of StFeNi-BC and StFeNi-BC-350 were successfully fabricated and applied in removing Pb(II) from aqueous solutions. The absorption of Pb(II) by StFeNi-BC and StFeNi-BC-350 were controlled by monolayer chemisorption and their maximum adsorption capacities were 122.767 and 148.043 mg/g, respectively. Mechanism studies showed that electrostatic attraction, ion exchange, complexation and physical adsorption occurred on the adsorbent surface. Studies on the influence of co-existing metal ions and water matrices on adsorption of Pb(II) demonstrated that StFeNi-BC-350 displayed high anti-interfering ability and promising application prospect for Pb(II) removal. In addition, StFeNi-BC-350 was applied in soil-wheat pot systems to further investigate its influence on reducing Pb induced oxidative stress on wheat. Compared with the control, the addition of StFeNi-BC-350 increased the biomass and total chlorophyll content in leaves, and decreased the activity of antioxidant enzymes (MDA, SOD, CAT, POD) together with ROS fluorescence intensity of wheat. The results indicated that StFeNi-BC-350 could alleviate Pb(II) stress of wheat. Furthermore, the addition of StFeNi-BC-350 improved the physicochemical properties of the soil, and increased the abundance as well as the number of soil microorganisms, thereby alleviating Pb stress on wheat. Therefore, StFeNi-BC-350 is suitable for the practical treatment of Pb-contaminated water and soil.

Enhancing encapsulation of curcumin by pH-driven and sodium alginate blending with ovalbumin as a carrier

Curcumin is a hydrophobic polyphenol with various health benefits, but its poor water solubility and stability limit its application in the food and pharmaceutical industries. In this study, a pH-driven method was developed to prepare ovalbumin (OVA)-curcumin nanocomplexes without organic solvents, reducing the environmental impact. The results showed that curcumin was encapsulated in OVA with a high efficiency of over 95% and remained in an amorphous state within the protein molecules. Molecular docking and spectroscopic analyses revealed that curcumin was mainly bound and stabilized by hydrogen bonds and hydrophobic interactions in the hydrophobic core of OVA. The binding strength of the intermediate stage of the pH-driven method was stronger than that of the final stage, due to the exposure of OVA molecular binding sites and the involvement of electrostatic attraction. Furthermore, the potential of polysaccharide blending to enhance the stability of the nanocomplexes was investigated. The results showed that sodium alginate effectively enhanced the photostability and thermal stability of the OVA-curcumin nanocomplexes by co-solubilization and electrostatic complex formation. In addition, simulated in vitro digestion also demonstrated that the pH-driven method combined with polysaccharide blending increased the bioaccessibility of curcumin in nanocomplexes from 17.79% to 52.54%. Therefore, the pH-driven method coupled with polysaccharide blending ensures the encapsulation and stabilization of hydrophobic bioactive substances for use in their delivery systems to improve bioaccessibility.

Emulsifying properties of O/W emulsion stabilized by soy protein isolate and γ-polyglutamic acid electrostatic complex.

In order to improve the emulsifying properties of soy protein around isoelectric point, soy protein isolate (SPI) and γ-polyglutamic acid (γ-PGA) complexes were prepared by electrostatic interaction. The formation of SPI-γ-PGA electrostatic complex and emulsifying properties were investigated by monitoring turbidity, zeta potential, intrinsic fluorophores, emulsion characterization, and microstructure observation. The results showed that the formation of SPI-γ-PGA electrostatic complex was identified through turbidimetric analysis and zeta-potential measurement. Intrinsic fluorescence spectrum indicated internal structure changes of electrostatic complexes. Furthermore, SPI-γ-PGA complex-stabilized emulsions showed better stability with small droplet sizes and slow growth as well as the uniform microstructure around the isoelectric point (pH 4.0-5.0) than SPI-formed emulsions. Under the different thermal treatments and ionic strengths, emulsions stabilized by SPI-γ-PGA-soluble complex resulted in improved emulsion stability to environmental stresses. This may be attributed to the increased steric repulsion and electrostatic repulsion by SPI-γ-PGA complexes at oil-water interfaces. The findings derived from this research would provide theoretical reference about SPI-γ-PGA electrostatic complex that can be applied in acid beverages and developed a novel plant-based sustainable stabilizer for emulsions. PRACTICAL APPLICATION: The electrostatic interaction between SPI and γ-PGA improved the emulsifying characteristics of soy protein around isoelectric point. The results derived from this research would expand applications of SPI-γ-PGA-soluble electrostatic complex that can be applied in acid beverages, as well as a novel plant-based sustainable stabilizer for emulsions.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Cu2O/Ag-coated wood-based biochar composites for efficient adsorption/photocatalysis synergistic degradation of high-concentration azo dyes

In order to effectively eliminate organic azo dyes with high concentrations from aqueous environments, novel adsorption/photocatalysis composites were prepared using Cu2O/Ag-coated carriers based on renewable wood-based biochar (MBC). The adsorption process of the prepared MBC@Cu2O/Ag-3 under electrostatic attraction, hydrogen bonding, and complexation effects was conformed to the proposed second-order kinetic model, and the total sorption capacity of Congo red (CR) and methyl orange (MO) reached 264.55 and 178.63 mg g−1, respectively. Moreover, the coordinated interaction of MBC, Cu2O, and Ag enhanced the visible light absorptivity, which further facilitated the effective dissociation of light-generated electrons from holes. The removal rates of CR and MO by MBC@Cu2O/Ag-3 in the presence of visible light were up to 98.4 % and 97.8 %, respectively. In addition, free radical capture and electron spin resonance (ESR) spectroscopy analyses indicated that superoxide (·O2-) and hydroxyl (·OH) radicals were major activators during the photocatalytic progression, and the adsorption/photocatalysis mechanism was elucidated through a series of characterization experiments. This work shows that the utilization of natural biomass materials for the preparation of adsorption/photocatalysis composites with high added value can significantly contribute to water environmental protection and sustainable development.

Hybrid mesoporous silica materials templated with surfactant polyion complex (SPIC) micelles for pH-triggered drug release

New Surfactant PolyIon Complex (SPIC) micelles were assembled by electrostatic complexation of an antibacterial cationic surfactant, cetylpyridinium chloride (CPC), and a double hydrophilic block copolymer (DHBC) containing a neutral comb block of poly(oligo(ethylene glycol)) methyl ether acrylate (PEOGA) and a weak polyacid block of poly(acrylic acid) (PAA). The corresponding SPIC micelles, with a CPC/PAA core and a PEOGA corona, were successfully used as structure directing and functionalizing agents in a soft and sustainable sol-gel strategy, yielding hybrid mesoporous silica (MS) materials with a monomodal pore size distribution centred at 2.8 nm. The influence of synthesis parameters, including the pH, concentrations and ratios of components, was systematically investigated. The obtained hybrid MS materials were intrinsically functional, with PEOGA blocks anchored in silica walls via H-bonding, while weak polyacid blocks, complexed with CPC, were confined within the mesopores. The response of the materials to pH changes (pH 7.4, 4.2 and 3) indicated remarkable stability of the anchored DHBC, while CPC was selectively released under the acidic conditions typical of orodental biofilm microenvironments. This result is noteworthy, since the release of encapsulated amphiphilic drugs into water is less favorable than that of hydrophilic drugs. Owing to the control of their pore and functionality properties, ordered hybrid silica materials templated and functionalized with SPIC systems will be materials of choice for developing pH-responsive biomedical devices using wet processing techniques.

Enhanced Antibacterial Efficiency and Anti-Hygroscopicity of Gum Arabic-ε-Polylysine Electrostatic Complexes: Effects of Thermal Induction.

The aim of this investigation was to scrutinize the effects of a thermal treatment on the electrostatic complex formed between gum arabic (GA) and ε-polylysine (ε-PL), with the goal of improving the antibacterial properties and reducing the hygroscopicity of ε-PL. The heated complex with a ratio of 1:4 exhibited an encapsulation efficiency of 93.3%. Additionally, it had an average particle size of 350.3 nm, a polydispersity index of 0.255, and a zeta potential of 18.9 mV. The formation of the electrostatic complex between GA and ε-PL was confirmed through multispectral analysis, which demonstrated the participation of hydrogen bonding and hydrophobic and electrostatic interactions, as well as the enhanced effect of heat treatment on these forces within the complex. The complex displayed a core-shell structure, with a regular distribution and a shape that was approximately spherical, as observed in the transmission electron microscopy images. Additionally, the heated GA-ε-PL electrostatic composite exhibited favorable antibacterial effects on Salmonella enterica and Listeria monocytogenes, with reduced minimum inhibitory concentrations (15.6 μg/mL and 62.5 μg/mL, respectively) and minimum bactericidal concentrations (31.3 μg/mL and 156.3 μg/mL, respectively) compared to free ε-PL or the unheated electrostatic composite. Moreover, the moisture absorption of ε-PL reduced from 92.6% to 15.0% in just 48 h after being incorporated with GA and subsequently subjected to heat. This research showed a way to improve the antibacterial efficiency and antihygroscopicity of ε-PL, reducing its application limitations as an antimicrobial substance to some extent.