Extraction of rare earth elements from monazite leach liquor using functionalized chitosan sorbents derived from shrimp waste.

With the growing need for high-purity rare-earth elements (REEs), the separation of these REEs has received much attention recently. The objective of this research is to produce chitosan from shrimp waste, then modify it with different functionality, and investigate the adsorption properties of chitosan adsorbents towards La(III) ions. First, from shrimp waste, chitosan (ch) with a significant degree of deacetylation, purity, and solubility was produced. The purified chitosan was cross-linked with epichlorohydrin (ep), and then, it was modified with 3,6,9,12-tetraazatetradecane-1,14-diamine (HA) to produce polyaminated chitosan (HA@ep@Ch). The polycarboxylated/imine chitosan (CM@HA@ep@Ch) was obtained by treating polyaminated chitosan with chloroacetic acid in isopropyl alcohol. The chitosan adsorbents were characterized and applied for lanthanum recovery from synthetic and monazite leach liquor samples. The factors controlling the recovery process were studied and discussed. The performance of the adsorbents was achieved through equilibrium, dynamic, and isothermal studies. HA@ep@Ch and CM@HA@ep@Ch showed good performance for lanthanum recovery with a maximum capacity of 114.52 and 141.76 mg/g at 330 K, respectively. The isotherm parameters refer to the monolayer of lanthanum adsorbed into the adsorbents through chelation and ion exchange mechanisms. A 0.5-M HCl solution was found effective to elute 95.8% of the adsorbed lanthanum on HA@ep@Ch, and 93.4% of the adsorbed lanthanum on CM@HA@ep@Ch. The adsorbents showed greater selectivity in extracting La, Ce, Pr, Nd, and Sm (62-75%) from REE leach liquid compared to extracting other REEs (20-41%).

Phosphonation of Alginate-Polyethyleneimine Beads for the Enhanced Removal of Cs(I) and Sr(II) from Aqueous Solutions.

Although Cs(I) and Sr(II) are not strategic and hazardous metal ions, their recovery from aqueous solutions is of great concern for the nuclear industry. The objective of this work consists of designing a new sorbent for the simultaneous recovery of these metals with selectivity against other metals. The strategy is based on the functionalization of algal/polyethyleneimine hydrogel beads by phosphonation. The materials are characterized by textural, thermo-degradation, FTIR, elemental, titration, and SEM-EDX analyses to confirm the chemical modification. To evaluate the validity of this modification, the sorption of Cs(I) and Sr(II) is compared with pristine support under different operating conditions: the pH effect, kinetics, and isotherms are investigated in mono-component and binary solutions, before investigating the selectivity (against competitor metals) and the possibility to reuse the sorbent. The functionalized sorbent shows a preference for Sr(II), enhanced sorption capacities, a higher stability at recycling, and greater selectivity against alkali, alkaline-earth, and heavy metal ions. Finally, the sorption properties are compared for Cs(I) and Sr(II) removal in a complex solution (seawater sample). The combination of these results confirms the superiority of phosphonated sorbent over pristine support with promising performances to be further evaluated with effluents containing radionuclides.

Electro-analytical sensing of anti-hypotensive agents: application to dosage forms and human urine.

A new and valid method was developed for the quantitative voltammetric analysis of midodrine hydrochloride (MID) in pharmaceutical tablets (Midodrine) and biological samples. The method is based on electro-oxidation of MID supported by both disposable pencil electrode (PE) and glassy carbon electrode (GCE). The analysis was carried out using cyclic voltammetry, differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. The proposed analytical method was validated according to ICH guidelines. MID was successively assayed at concentration ranges of 1.15-6.55 and 0.58-3.05 µg mL-1 at PE. Also, MID was successively assayed at concentration ranges of 1.15-5.28 and 2.86-27.6 µg mL-1 at GCE for DPV and SWV methods, respectively. The proposed method was successfully used for the analysis of MID in its dosage form and human urine with good recoveries of 99.66 ± 0.33, 99.8 ± 0.45 at PE and 99.8 ± 0.25, 98.7 ± 1.27 at GCE for the DPV and SWV methods, respectively. The suggested method could be applied to the studied drug in the quality control lab as well as in its pharmacokinetic studies.

Synthesis of Eco-Friendly Biopolymer, Alginate-Chitosan Composite to Adsorb the Heavy Metals, Cd(II) and Pb(II) from Contaminated Effluents.

Efficient removal of Cd(II) and Pb(II) from contaminated water is considered a fundamental point of view. Synthetic hydrogel biopolymers based on chitosan and alginate (cost-effective and eco-friendly) were successfully designed and characterized by highly efficient removal contaminants. The sorbents are characterized by FTIR, SEM-EDX, TGA, XPS analyses and textural properties which are qualified by N2 adsorption. The sorption properties are firstly investigated by the effect of pH, sorption isotherms, uptake kinetics, and selectivity from multi-metal solution with equi-molar concentration. The sorbent with 1:3 ratios (of chitosan and alginate respectively) is the most effective for metal removal (i.e., 0.81 mmol Cd g-1 and 0.41 mmol Pb g-1). Langmuir and Sip's models fitted better the adsorption isotherms compared to the Freundlich model. Uptake kinetics was well fitted by pseudo-first-order rate equation, while the saturation was achieved within 40 min. The sorbent shows good reproducibility through duplicate the experiments with negligible decreasing efficiency (>2.5%). The sorbent was applied for water treatment on samples collected from the industrial area (i.e., 653 and 203 times over the MCL for Cd(II) and Pb(II) respectively according to WHO). The concentration of Cd and Pb was drastically decreased in the effluents as pH increased with removal efficiency up to 99% for both elements at pH 5.8 and SD equivalent 1 g L-1 for 5 h.

Solution Blowing Spinning Technology towards Green Development of Urea Sensor Nanofibers Immobilized with Hydrazone Probe.

Cellulose has been one of the most widespread materials due to its renewability, excellent mechanical properties, biodegradability, high absorption ability, biocompatibility and cheapness. Novel, simple and green colorimetric fibrous film sensor was developed by immobilization of urease enzyme (U) and tricyanofuran hydrazone (TCFH) molecular probe onto cellulose nanofibers (CNF). Cellulose acetate nanofibers (CANF) were firstly prepared from cellulose acetate using the simple, green and low cost solution blowing spinning technology. The produced CANF was exposed to deacetylation to introduce CNF, which was then treated with a mixture of TCFH and urease enzyme to introduce CNF-TCFH-U nanofibrous biosensor. CNF were reinforced with tricyanofuran hyrazone molecular probe and urease enzyme was encapsulated into calcium alginate biopolymer to establish a biocomposite film. This CNF-TCFH-U naked-eye sensor can be applied as a disposable urea detector. CNF demonstrated a large surface area and was utilized as a carrier for TCFH, which is the spectroscopic probe and urease is a catalyst. The biochromic CNF-TCFH-U nanofibrous biosensor responds to an aqueous medium of urea via a visible color signal changing from off-white to dark pink. The morphology of the generated CNF and CNF-TCFH-U nanofibrous films were characterized by different analytical tools, including energy-dispersive X-ray patterns (EDX), polarizing optical microscope (POM), Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). SEM images of CNF-TCFH-U nanofibers demonstrated diameters between 800 nm and 2.5 µm forming a nonwoven fabric with a homogeneous distribution of TCFH/urease-containing calcium alginate nanoparticles on the surface of CNF. The morphology of the cross-linked calcium alginate nanoparticles was also explored using transmission electron microscopy (TEM) to indicate an average diameter of 56-66 nm. The photophysical performance of the prepared CNF-TCFH-U was also studied by CIE Lab coloration parameters. The nanofibrous film biosensor displayed a relatively rapid response time (5-10 min) and a limit of detection as low as 200 ppm and as high as 1400 ppm. Tricyanofuran hydrazone is a pH-responsive disperse dye comprising a hydrazone detection group. Determination of urea occurs through a proton transfer from the hydrazone group to the generated ammonia from the reaction of urea with urease.

Modeling climatic effect on physiochemical parameters and microorganisms of Stabilization Pond Performance.

The present study was carried out to evaluate the relationship between physiochemical parameters, microorganisms, wastewater and climate in Stabilization Pond Performance. This study performed as a post-treatment after the secondary wastewater treatment using extended aeration in Rashid city, Egypt. The model of the extended aeration as secondary wastewater treatment was developed based on the combination with lagoon after the secondary sedimentation basin. The Climatic functions have an important impact on the mechanism of ponds as it actuates vertical mixing of the pond contents. The interaction between bacteria, algae and other organisms are the main idea of oxidation pond treatment beside the relationship between the climatic functions, physiochemical parameters and microorganisms biomass. The removal of biodegradable organic loads specially nitrogen and phosphorous are perfectly happens in oxidation maturation ponds which reflects a higher treatment efficiency of the sewage by 98%-99% of Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and heavy metals. The study included some recommendations aiming at improving both water quality and its recycling in plants irrigation.

Nanomaterial-Based Carbon Paste Electrodes for Voltammetric Determination of Naproxen in Presence of Its Degradation Products.

The present work describes a novel, simple, and fast electroanalytical methodology for naproxen (NAP) determination in pharmaceutical formulations and biological fluids in the presence of its degradation products. Carbon paste electrodes (CPEs) modified with different carbon nanomaterials, namely, glassy carbon powder (GCE), multiwall carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), graphene nanosheets (Gr), and graphene oxides (GO) were tested. Comprehensive studies were performed on the electrode matrix composition including the nature of the pasting liquids, pH, carbon nanomaterials, and mode of electrode modification. Two anodic oxidation peaks were recorded at 0.890 and 1.18 V in 1 × 10-1 mol·L-1 phosphate buffer solution at pH 6. Oxidation of naproxen (NAP) is an irreversible diffusion-controlled process. Calibration plots were rectilinear in the concentration ranging from 0.067 to 1.0 µg·mL-1 with correlation coefficient 0.9979. Photodegradation of NAP resulted in disappearance of the oxidation peak at 1.18 V, allowing simultaneous determination of NAP in presence of its degradation product. The achieved high sensitivity and selectivity suggest the application of the proposed protocol for naproxen determination in pharmaceutical preparations and human blood plasma.

Voltammetric Assay of Metformin Hydrochloride Using Pyrogallol Modified Carbon Paste Electrode.

The electrooxidative behavior and determination of metformin hydrochloride, anti-hyperglycemic drug, on a pyrogallol modified carbon paste electrode were investigated using cyclic voltammetry and differential pulse voltammetry. Metformin hydrochloride shows an irreversible oxidation behavior over a wide interval of pH (Britton-Robinson buffers, pH 2-9). The peak current varied linearly in the range comprised between 8.0 × 10(-7) and 6.0 × 10(-6) mol/L with detection limit of 6.63 × 10(-8) mol/L and limit of quantification of 2.21 × 10(-7) mol/L. The method was proposed for the determination of metformin hydrochloride in dosage forms and urine.