Xiaohong Cao

Self-assembled micellar nanoparticles of a novel star copolymer for thermo and pH dual-responsive drug release

An amphiphilic star block copolymer comprised of a hydrophobic PMMA block and a hydrophilic tri-arm poly(NIPAAm-co-DMAEMA) block was synthesized by copolymerization of NIPAAm and DMAEMA, with Ce(4+) ions and tris(hydroxymethyl)methylamine as a redox initiatory system. The star copolymer undergoes self-assembly to the micellar nanoparticles with a core-shell structure and the thermo/pH dual-response, originated from the thermo-sensitivity of PNIPAAm and the pH-sensitivity of PDMAEMA. A fluorescence probe study showed the pH-dependent low CMCs (7.5 to 11.2 mg/L) of the micelles, confirming the formation of stable micelles. Morphological investigations showed that the blank and drug-loaded micelles both had spherical and uniform shapes. The sizes of the blank and drug-loaded nanoparticles were between 80 and 120 nm, depending on the given pH. The LCSTs of the star copolymer were determined to be 32 degrees C, 36.6 degrees C and 39.5 degrees C, corresponding to pH 5, pH 7.4 and pH 9, respectively, demonstrating a pH-dependent thermo-response. As a drug delivery, the micellar nanoparticles showed the dual-responsive release profiles in vitro, which were confirmed by the drug release studies. The obtained results showed the thermo-triggered accelerated release at pH 7.4, and the pH-triggered accelerated release at 37 degrees C, indicating the micelles nanoparticles would be a promising site-specific drug delivery for enhancing the accumulation of drug in targeting pathological areas.

Adsorption of uranium from aqueous solution using biochar produced by hydrothermal carbonization

The ability of biochar produced by hydrothermal carbonization (HTC) has been explored for the removal and recovery of uranium from aqueous solutions. The micro-morphology and structure of HTC were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The HTC showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 50xa0min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, △G°(298xa0K), △H° and △S° were determined to be −14.4, 36.1xa0kJxa0mol−1 and 169.7xa0Jxa0mol−1xa0K−1, respectively, which demonstrated the sorption process of HTC towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed HTC could be effectively regenerated by 0.05xa0mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9xa0%) of U(VI) from 1.0 L industry wastewater containing 15.0xa0mg U(VI) ions was possible with 2.0xa0g HTC.

Sorption study of uranium from aqueous solution on ordered mesoporous carbon CMK-3

The ability of ordered mesoporous carbon CMK-3 has been explored for the removal and recovery of uraium from aqueous solutions. The textural properties of CMK-3 were characterized using small-angle X-ray diffraction and N2 adsorption–desorption, and the BET specific surface area, pore volume and the pore size were 1143.7xa0m2/g, 1.10xa0cm3/g and 3.4xa0nm. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The CMK-3 showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 35xa0min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir and Freundlich isotherm. The thermodynamic parameters, ∆G°(298xa0K), ∆H° and ∆S° were determined to be −7.7, 21.5xa0kxa0Jxa0mol−1 and 98.2xa0Jxa0mol−1xa0K−1, respectively, which demonstrated the sorption process of CMK-3 towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed CMK-3 could be effectively regenerated by 0.05xa0mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9xa0%) of U(VI) from 1.0 L industry wastewater containing 15.0xa0mg U(VI) ions was possible with 2.0xa0g CMK-3.

Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO3/Ca–U(VI)–CO3 complexes

The influence of U(VI)-CO3 and Ca-U(VI)-CO3 complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (qe) and distribution constant (Kd) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the qe and Kd values of NZVI were 5-10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0-3.5 times higher than the 100% red soil column. The U(VI)-CO3 complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO-UO2CO3(-) or SO-UO2 (CO3)2(3-). XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

Biosorption characteristics of uranium(VI) from aqueous solution by pummelo peel

The biomass pummelo peel was chosen as a biosorbent for removal of uranium(VI) from aqueous solution. The feasibility of adsorption of U(VI) by Pummelo peel was studied with batch adsorption experiments. The effects of contact time, biosorbent dosage and pH on adsorption capacity were investigated in detail. The pummelo peel exhibited the highest U(VI) sorption capacity 270.71xa0mg/g at an initial pH of 5.5, concentration of 50xa0μg/mL, temperature 303xa0K and contacting time 7xa0h. The adsorption process of U(VI) was found to follow the pseudo-second-order kinetic equation. The adsorption isotherm study indicated that it followed both the Langmuir adsorption isotherm and the Freundlich adsorption isotherm. The thermodynamic parameters values calculated clearly indicated that the adsorption process was feasible, spontaneous and endothermic in nature. These properties show that the pummelo peel has potential application in the removal of the uranium(VI) from the radioactive waste water.

Sorption study of uranium on carbon spheres hydrothermal synthesized with glucose from aqueous solution

The ability of oxygen-rich carbon spheres (CSs) produced by hydrothermal carbonization with the glucose has been explored for the removal and recovery of uranium from aqueous solutions. The micro-morphology and structure of CSs were characterized by FT-IR and SEM. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The CSs showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 25xa0min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, △G°(298xa0K), △H° and △S° were determined to be −16.88, 12.09xa0kJxa0mol−1 and 197.87xa0Jxa0mol−1xa0K−1, respectively, which demonstrated the sorption process of CSs towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed CSs could be effectively regenerated by 0.05xa0mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9xa0%) of U(VI) from 1.0xa0L industry wastewater containing 15.0xa0mg U(VI) ions was possible with 3.0xa0g CSs.

Adsorptive removal of U(VI) from aqueous solution by hydrothermal carbon spheres with phosphate group

The phosphorylated hydrothermal carbon spheres (HCS-PO4) were developed by functionalizing hydrothermal carbon spheres (HCS) with o-phosphoethanolamine, and the structure and textural property were characterized by SEM and FT-IR. The parameters that affect the uranium(VI) sorption, such as solution pH, initial U(VI) concentration, contact time, and temperature, had been investigated. The HCS-PO4 showed the highest uranium sorption capacity at initial pH 6.0 and contact time of 120xa0min. The adsorption kinetics was better described by the pseudo-second-order model, and the adsorption process could be well defined by the Langmuir isotherm and the maximum monolayer adsorption capacity increased from 80.00 to 434.78xa0mg/g after phosphorylation. The thermodynamic parameters, ∆G° (298xa0K), ∆H° and ∆S°, demonstrated shown that the sorption process of U(VI) onto HCS-PO4 was feasible, spontaneous and endothermic in nature. The spent HCS-PO4 could be effectively regenerated by 0.1xa0mol/L EDTA solution for the removal and recovery of U(VI) and reused for ten cycles at least. Selective adsorption studies showed that the HCS-PO4 could selectively remove U(VI), and the selectivity coefficients of HCS in the presence of co-existing ions, Mg(II), Na(I), Zn(II), Mn(II),Co(II), Ni(II), Sr(II), Cs(I) and Hg(II) improved after functionalization.

Removal of uranium(VI) from aqueous solutions by new phosphorus-containing carbon spheres synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid

The novel phosphorus-rich hydrothermal carbon spheres (HCSs–PO4) have been synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid. The textural and surface chemistry properties were characterized using Boehm titrations, scanning electron microscopy and Fourier transform infrared spectrometer. The content of oxygen-containing functional groups on the surface of HCSs increased from 0.053 to 1.009xa0mmolxa0g−1 by phosphate group modification. The adsorption ability of HCSs–PO4 has been explored for the removal of uranium from aqueous solutions. The adsorption kinetic data were best described by the pseudo-second-order equation. Adsorption process could be well defined by the Langmuir isotherm, the adsorption capacity of HCSs increased from 80.00 to 285.70xa0mgxa0g−1 after phosphate group modification. And thermodynamic parameters indicated the adsorption process was feasible,endothermic and spontaneous. Selective adsorption studies showed that the HCSs–PO4 could selectively remove U(VI), and the selectivity coefficients had been improved in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). Complete removal (99.9xa0%) of U(VI) from 1.0xa0L industry wastewater containing 15.0xa0mg U(VI) ions was possible with 12.0xa0g HCSs–PO4.

Pre-concentration and determination of trace uranium (VI) in environments using ion-imprinted chitosan resin via solid phase extraction

The uranyl-ion-imprinted and non-imprinted cross-linked chitosan resins possessing quinoline-8-ol moiety have been prepared. In all the cases, a significant imprinting effect was noticed on comparing percent extraction of uranium (VI). The resulting ion-imprinted resin was used for solid phase extractive preconcentration of uranium (VI) prior to its determination by spectrophotometry. Experimental variables that influence the quantitative extraction of uranium (VI) were optimized by both static and column methods. The retention capacity found for uranium (VI) was 218 mg g-1 of resin which is higher than the corresponding non-imprinted resins and other solid phase extraction sorbents possessing quinoline-8-ol moiety. The optimum pH range was 4.5-7.0. Uranium adsorbed was easily and quantitatively eluted with 1 mol L-1 HCl (10 mL) at a flow rate of 2 mL min-1. Interference studies showed a high tolerance of diverse ions and electrolyte species. The limit of detection was 2 µg L-1 and the dynamic linear range was 5-100 µg L-1. The accuracy of the developed method was tested with one uranium ore standard reference material. Furthermore, the proposed method was successfully applied for the determination of uranium in contaminated soil and sediment samples.

Recycle of U(VI) from aqueous solution by situ phosphorylation mesoporous carbon

A new phosphorylated mesoporous carbon (CMK-3-PO4) was synthesized by situ phosphorylation of concentrated phosphoric acid (85xa0%) using mesoporous carbon (CMK-3) as a template. The maximum monolayer adsorption capacity of adsorbents increased from 133.5xa0mgxa0g−1 (CMK-3) to 485.4xa0mgxa0g−1 (CMK-3-PO4) due to the extended oxygen functional groups, and the U(VI) adsorption on CMK-3-PO4 was endothermic and spontaneous in nature. The selective sorption ability of U(VI) was significantly improved after phosphorylation. The U(VI) in the CMK-3-PO4 could been eluted by 1.0xa0molxa0L−1 HCl and also had good reusing property, and this may offer the CMK-3-PO4 very promising application prospects.