Harnessing the power of polyethyleneimine in modifying chitosan surfaces for efficient anion dyes and hexavalent chromium removal.

In this investigation, synthesis of a surface-functionalized chitosan known as amino-rich chitosan (ARCH) was achieved by successful modification of chitosan by polyethyleneimine (PEI). The synthesized ARCH was characterized by a specific surface area of 8.35 m2 g-1 and a microporous structure, with pore sizes predominantly under 25 nm. The Zeta potential of ARCH maintained a strong positive charge across a wide pH range of 3-11. These characteristics contribute to its high adsorption efficiency in aqueous solutions, demonstrated by its application in removing various anionic dyes, including erioglaucine disodium salt (EDS), methyl orange (MO), amaranth (ART), tartrazine (TTZ), and hexavalent chromium ions (Cr(VI)). The adsorption capacities (Qe) for these contaminants were measured at 1301.15 mg g-1 for EDS, 1025.45 mg g-1 for MO, 940.72 mg g-1 for ART, 732.96 mg g-1 for TTZ, and 350.15 mg g-1 for Cr(VI). A significant observation was the rapid attainment of adsorption equilibrium, occurring within 10 min for ARCH. The adsorption behavior was well-described by the Pseudo-second-order and Langmuir models. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic in nature. Additionally, an increase in temperature was found to enhance the adsorption capacity of ARCH. The material demonstrated robust stability and selective adsorption capabilities in varied conditions, including different organic compounds, pH environments, sodium salt presence, and in the face of interfering ions. After five cycles of adsorption, ARCH maintained about 60% of its initial adsorption capacity. Due to its efficient adsorption performance, simple synthesis process, low biological toxicity, and cost-effectiveness, ARCH is a promising candidate for future water treatment technologies.

Efficient adsorption of selenium (Se(IV) and Se(VI)) from water using Acacia senegal polysaccharide with multiple amine groups: Synthesis and application.

In this study, an amine-rich gel (ARAS) was prepared by chemically altering Acacia senegal (AS). ARAS acts as an adsorbent for selenium. Owing to the introduction of amino functional groups and a remarkable specific surface area (91.89 g/m2), ARAS shows maximum adsorption capacities at 75 and 130 mg g-1 for Se(IV) and Se(VI), respectively. The removal efficiency of ARAS is higher (ωSeIV = 98.2 % and ωSeVI = 98.6 %) at lower concentrations (CSeIV = 100 ppm and CSeVI = 95 ppm) and the adsorption equilibrium is achieved within 60 min. The adsorption process of Se (IV) and Se (VI) via ARAS is elucidated using the Quasi-Second-Order kinetic and Langmuir models. The enhanced adsorption capacity of the adsorbent could be attributed to the synergistic effects of electrostatic attraction, hydrogen bonding, and specific physicochemical properties. Thermodynamic studies reveal that the surface adsorption process is spontaneous and exothermic. Notably, ARAS maintains remarkable adsorption stability under a variety of solution conditions, including variable pH (4-11), NaCl concentrations (0-1 M), and the presence of organic solvents. It retains approximately 60 % of its initial adsorption capacity for Se(IV) and Se(VI) after three adsorption cycles. Therefore, ARAS with its cost-effectiveness and exceptional performance shows considerable potential for applications in water treatment.

One-pot synthesis of robust dendritic sulfur quantum dots for two-photon fluorescence imaging and "off-on" detection of hydroxyl radicals and ascorbic acid.

The straightforward preparation of fluorescent sulfur quantum dots (SQDs) with good photostability and biocompatibility and multifunction remains a challenge. Herein, a simple method to improve the performance of SQDs is reported, that is, using hyperbranched polyglycerol (HPG) as a ligand to direct the synthesis of dendritic HPG-SQD nanocomposites from cheap elemental sulfur. Thanks to the protection of HPG, the HPG-SQDs show much better biocompatibility and photostability as compared with the widely reported polyethylene glycol (PEG) ligand-capped SQDs (PEG-SQDs). In addition, the HPG-SQDs also present excellent aqueous solubility, stable fluorescence against environmental variation, good cell uptake capability, and strong single- and two-photon fluorescence. Moreover, the HPG-SQDs display sensitive and selective fluorescence "off-on" behavior to hydroxyl radicals (˙OH) and ascorbic acid (AA), respectively, and thereby hold potential as a fluorescent switch to detect ˙OH and AA. For the first time, the utilization of two-photon fluorescence of HPG-SQDs to monitor ˙OH and AA in cells is demonstrated in this study.

Facile synthesis of carboxymethyl cellulose sulfur quantum dots for live cell imaging and sensitive detection of Cr(VI) and ascorbic acid.

Nowadays the synthesis of stable fluorescent sulfur quantum dots (SQDs) remains a big challenge. Herein, the utilization of carboxymethyl cellulose (CMC) to synthesis of SQDs is reported. Benefiting from the unique composition and structure of CMC macromolecule, the resulted CMC-SQDs simultaneously show high aqueous dispersibility and stability, tunable emission, stable fluorescence and low cytotoxicity, which make them promising for working as a fluorescent probe. Fluorescence detection experiments suggested that the CMC-SQDs could serve as a fluorescence on-off-on switch to sensitive and selective detection of Cr(VI) and ascorbic acid (AA) based on the inner filter effect (IFE). The limit of detection towards Cr(VI) and AA can reach 0.024 and 0.18 µM with linear range of 0.5-225 and 1-300 µM, respectively, which compares favorably to other reported fluorescent probes. In addition, the employment of fluorescent CMC-SQDs for practical detection of Cr(VI) and AA was also studied.

Facile synthesis of amphiphilic peach gum polysaccharide as a robust host for efficient encapsulation of methylene blue and methyl orange dyes from water.

Despite impressive progress of macromolecular encapsulation technique based on hyperbranched polymer (HP), the use of natural HP for guest encapsulation has rarely been reported. Herein, we present the simple synthesis of amphiphilic PGP-DC from natural peach gum polysaccharide (PGP) and demonstrate that the PGP-DC can be utilized as a robust host for encapsulation of dye molecules from water. The influences of initial dye concentration, dosage of PGP-DC, pH, ionic strength, and encapsulation mode on the encapsulation were systematically studied. The PGP-DC simultaneously exhibited fast encapsulation rate and superior encapsulation capability. Under optimal conditions, the encapsulation capacity of PGP-DC towards methylene blue (MB) (1 mM) can reach as high as 182.67 mg/g, which compares favorably to other separation techniques. Moreover, the MB-encapsulated PGP-DC could be well regenerated in acidic solution. Based on its simple synthetic process, excellent encapsulation performance and fine reusability, the PGP-DC holds great promise for using as a host for practical encapsulation applications.

Oxygen accelerated scalable synthesis of highly fluorescent sulfur quantum dots.

Here, we report a facile and efficient approach for the large-scale synthesis of highly fluorescent sulfur quantum dots (SQDs) from inexpensive elemental sulfur under a pure oxygen (O2) atmosphere. The important finding of this work is that the polysulfide (S x 2-) ions could be oxidized to zero-valent sulfur (S[0]) by O2, which is the accelerator of the reaction. The SQDs prepared by this method possess nearly monodisperse size (1.5-4 nm), high fluorescence quantum yield (21.5%), tunable emission, and stable fluorescence against pH change, ionic strength variation and long-term storage. Moreover, the reaction yield of SQDs reached as high as 5.08% based on the content of S element in SQDs, which is much higher than other reported approaches (generally <1%). The prepared SQDs could be easily processed for widespread applications thanks to their low toxicity and superior dispersibility both in water and common organic solvents. These high-quality SQDs may find applications similar to or beyond those of carbon QDs and silicon QDs.

Superior amine-rich gel adsorbent from peach gum polysaccharide for highly efficient removal of anionic dyes.

Herein, we demonstrated the potential of peach gum polysaccharide-based amine-rich gel (ARG) as an efficient adsorbent for removal of anionic dyes from water. The adsorption performance of ARG was systematically studied by choosing methyl orange (MO) and amaranth (ART) as representative anionic dyes. The effects of various parameters such as pH, ionic strength, temperature, initial dye concentration and contact time on the adsorption were investigated. The ARG exhibited superior adsorption selectivity and stable adsorption behaviors against variation of pH and ionic strength for anionic dyes. Adsorption process reached equilibrium within 10 min and showed good correlation with pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacity of ARG for MO and ART can reach 1949.5 and 1082.2 mg g-1, respectively. Based on its sustainable characteristic, low cost and excellent adsorption property, the ARG holds great promise for utilizing as an adsorbent for practical water treatment applications.

Facile Functionalization of Natural Peach Gum Polysaccharide with Multiple Amine Groups for Highly Efficient Removal of Toxic Hexavalent Chromium (Cr(VI)) Ions from Water.

The development of low-cost adsorbent with excellent adsorption property remains a big challenge. Herein, the functionalization of natural peach gum polysaccharide (PGP) with multiple amine groups for the removal of toxic Cr(VI) ions from water was studied. The obtained PGP-NH2 gel exhibited high-removal efficiency (>99.5%) toward Cr(VI) ions, especially with relatively low initial concentration of Cr(VI) ions (≤250 mg/L). The influences of pH, ionic strength, contact time, initial concentration, and temperature on the adsorption of Cr(VI) ions were systematically investigated. The PGP-NH2 gel showed rapid adsorption rate and could reach adsorption equilibrium within about 40 min. The Cr(VI) ion uptake process could be described by pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of PGP-NH2 gel could reach 188.32 mg/g. Thermodynamic investigation results indicated the spontaneous and exothermic characteristic of the uptake process. Moreover, the PGP-NH2 gel also exhibited favorable reusability, and 135.52 mg/g of adsorption capacity was retained even after being reused for five times. Considering its low cost and superior uptake property, the PGP-NH2 gel holds a great promise for employing as an adsorbent to treat Cr(VI) ion-containing wastewater.