Cu(II) Ion Adsorption by Aniline Grafted Chitosan and Its Responsive Fluorescence Properties

Functionalization of a cast NaAl/binary ZnO/SiO2 nanohybrid with amine and Schiff base ligands as an adsorbent of divalent cations in water system

Casting method was used to synthesize a novel sodium alginate nanohybrid functionalized with aminated ZnO/SiO2 Schiff base for adsorption of nickel (Ni2+) and copper (Cu2+) divalent cations in single and binary water systems. The cast Schiff base nanohybrids were investigated using FESEM, XRD, BET, FTIR, TGA, and XPS analyses. The influence of unfunctionalized binary ZnO/SiO2 nano oxides and aminated Schiff base ligands formed by the reaction between salicylaldehyde and O-phenylenediamine on the adsorption of Ni2+ and Cu2+ cations was evaluated. The results confirmed that the aminated Schiff base ligands led to a higher adsorption ability of the cast nanohybrids containing interaction of divalent cations with nitrogen and oxygen atoms, as well as carboxyl and hydroxyl groups. The adsorption kinetics and isotherm for both cations followed a double-exponential model and the Redlich-Peterson model, respectively. The maximum monolayer capacity was found to be 249.8 mg/g for Cu2+ cation and 96.4 mg/g for Ni2+ cation. Thermodynamic analysis revealed an endothermic and spontaneous adsorption process with an increase in entropy. Furthermore, the synthesized Schiff base adsorbent could be easily reused over five times. The simultaneous adsorption in binary system exhibited a higher adsorption selectivity of the cast Schiff base nanohybrid for Cu2+ cation compared to Ni2+ cation. It was found that the removal percentages of Cu2+ and Ni2+ from industrial electroplating wastewater were 91.3 and 64.5%, respectively. Lastly, cost analysis of the synthesized nanohybrid was investigated.

Development of a novel chitosan-based two-photon fluorescent nanoprobe with enhanced stability for the specific detection of endogenous H2O2

Hydrogen peroxide (H₂O₂) acts as an important reactive oxygen species (ROS) and maintains the redox equilibrium in organisms. Imbalance of H₂O₂ concentration is associated with the development of many diseases. Traditional small molecular based fluorescent probes often show drawbacks of cytotoxicity and easily metabolic clearance. Herein, a chitosan-based two-photon fluorescent nanoprobe (DC-BI) was constructed and applied for H₂O₂ detection in live organisms. DC-BI was composed by chitosan nanoparticles and a two-photon fluorophore of naphthalimide analogues (BI) with H₂O₂-responsive property. The structure of DC-BI was characterized by NMR, FTIR, XPS, XRD, DLS and MLS analyses. As study shown, the nanoprobe DC-BI exhibited improved distribution stability and smaller cytotoxicity. In the presence of H₂O₂, both the absorption and emission spectra show dramatic changes, the fluorescence intensity at 580 nm obviously enhanced. Furthermore, fluorescence imaging results indicate that DC-BI is capable of imaging endogenous H₂O₂ in cells and zebrafish. The design and development of chitosan-based nanoprobe DC-BI has provided a general example of nanoprobe construction with excellent distribution stability, two-photon property, and biocompatibility.

Electrochemical detection of copper(II) in environmental samples using Penicillium sp. IITISM_ANK1 based biosensor

Detection of toxic metals at the lowest of their concentration in a variety of matrices has become a necessity due to the widespread and persistent nature of the contaminant. In this context, biosensors provide a viable alternative to the large sophisticated instrumentation. This study focuses on the development of a cost-effective fungal biomass-based biosensor that can be used for the detection of Cu(II). The fungal cells were pretreated with formaldehyde and studied with various spectroscopic studies. It was observed that the carbonyl groups along with amine groups played role in the sorption of copper ions which were stripped in an electrolytic solution to quantify the metal. Herein the dried fungal biomass was chemically activated and used to prepare a novel graphite paste electrode by repurposing a plastic pipette tip. The factors affecting the detection signal were optimized in further study. The electrochemical characterization revealed that the prepared bio-electrode was capable of detecting Cu in the range of 1 × 10^-7 M to 2 × 10^-5 M.

Efficient adsorption of heavy metals from wastewater on nanocomposite beads prepared by chitosan and paper sludge

Chitosan was commonly used with inorganic salt and organic compounds to prepare adsorption material for water treatment. Different materials were mixed for the preparation, leading to a high cost for water treatment. Sludge from papermaking has abundant fiber and inorganic salt, which can reduce the addition of raw materials in preparing the adsorption material and thus lower the cost. This work used recycled industrial paper sludge to prepare adsorption material to remove heavy metals from wastewater. The adsorption properties of the prepared sludge-chitosan material for Cu²⁺ and Cr³⁺ in wastewater were investigated. The impacts of adsorption time, pH, and initial concentrations of Cu²⁺ and Cr³⁺ on adsorption amount were studied and optimized. The saturated adsorption capacity of sludge-chitosan material for Cu²⁺ and Cr³⁺ can reach 114.6 and 110.3 mg/g. The adsorption kinetics satisfied the pseudo-second-order model, indicating two modes, physical diffusion, and chem-sorption, in the heavy metal adsorption by the sludge-chitosan materials. Physical distribution has little Effect on chemical adsorption. The materials can be applied to treating Cu²⁺ and Cr³⁺ containing wastewater with the proposed cheap and readily available sludge-chitosan material. The results confirmed that sludge-chitosan material possessed good regeneration performance and was an ideal adsorbent.

Fluorescent dialdehyde-BODIPY chitosan hydrogel and its highly sensing ability to Cu2+ ion

Fluorescent hydrogel with proper hydrophilicity and thermal stability, excellent sensitivity and high selectivity has important practical and scientific significance, especially in heavy metal ion detection. In this work, by adjusting the content of [2, 6-Bis-[4-formylthiophene]]-1,3,5,7-tetramethyl-8-phenyl-4, 4-difluoroborazaindoloene (B3), as a cross-linking agent, a series of chitosan- fluoroboron dipyrrole-chitosan-based fluorescent hydrogels (CBC) with large stokes shift were designed and prepared. The hydrogels can be used as fluorescent probes for identifying Cu²⁺ in aqueous solution. The linear quenching range of Cu²⁺ is 0-50 μM, and the detection limit and quenching constant are 4.75 μM and 3.52 × 10⁴ M^-1, respectively. Under the interaction of Cu²⁺, the imine bond CN was converted to C- N bond, which causes the phenomenon of fluorescence quenching. In addition, relatively high crosslink density improves hydrophilicity and thermal stability of initial chitosan, and made the swelling ability better.

Poly (Amidehydrazide) Hydrogel Particles for Removal of Cu2+ and Cd2+ Ions from Water

Poly(amidoamine)s (PAMAM) are very effective in the removal of heavy metal ions from water due to their abundant amine and amide functional groups, which have a high binding ability to heavy metal ions. We synthesized a new class of hyperbranched poly(amidehydrazide) (PAMH) hydrogel particles from dihydrazides and N,N'-methylenebisacrylamide (MBA) monomer by using the A2 + B4 polycondensation reaction in an inverse suspension polymerization process. In Cd2+ and Cu2+ ion sorption tests, the synthesized dihydrazide-based PAMH hydrogel particles exhibited sorption capacities of 85 mg/g for copper and 47 mg/g for cadmium. Interestingly, the PAMH showed only a 10% decrease in sorption ability in an acidic condition (pH = 4) compared to the diamine-based hyperbranched PAMAM, which showed a ~90% decrease in sorption ability at pH of 4. In addition, PAMH hydrogel particles remove trace amounts of copper (0.67 ppm) and cadmium (0.5 ppm) in water, below the detection limit.

Modified Biopolymer Adsorbents for Column Treatment of Sulfate Species in Saline Aquifers

In the present study, variable forms of pelletized chitosan adsorbents were prepared and their sulfate uptake properties in aqueous solution was studied in a fixed-bed column system. Unmodified chitosan pellets (CP), cross-linked chitosan pellets with glutaraldehyde (CL-CP), and calcium-doped forms of these pellets (Ca-CP, Ca-CL-CP) were prepared, where the removal efficiencies and breakthrough curves were studied. Dynamic adsorption experiments were conducted at pH 4.5 and 6.5 with a specific flow rate of 3 mL/min, fixed-bed height of 200 mm, and an initial sulfate concentration of 1000 mg/L. Breakthrough parameters demonstrated that Ca-CP had the best sulfate removal among the adsorbents, where the following adsorption parameters were obtained: breakthrough time (75 min), exhaust time (300 min), maximum sulfate adsorption capacity (q_max; 46.6 mg/g), and sulfate removal (57%) at pH 4.5. Two well-known kinetic adsorption models, Thomas and Yoon-Nelson, were fitted to the experimental kinetic data to characterize the breakthrough curves. The fixed-bed column experimental results were well-fitted by both models and the maximum adsorption capacity (46.9 mg/g) obtained was for the Ca-CP adsorbent. A regeneration study over four adsorption-desorption cycles suggested that Ca-CP is a promising adsorbent for sulfate removal in a fixed-bed column system.