The enhancement effect of polycarboxylic acids on reductive dechlorination transformation of pentachlorophenol (PCP) reacting with iron oxides was studied in anoxic suspension. Batch experiments were performed with three species of iron oxides (goethite, lepidocrocite and hematite) and four species of polycarboxylic acids (oxalate, citrate, succinate, and tartrate) through anoxic abiotic reactors. The chemical analyses and morphological observation from scanning and transmission electron microscopy showed that different combinations between polycarboxylic acids and iron oxides produced distinct contents of Fe(II)-polycarboxylic ligand complexes, which significantly enhanced PCP transformation. Generation of the surface-bound Fe(II) depended on concentration of polycarboxylic acids. The optimal concentration for the enhancement was 2.0 mM oxalic acid. The dechlorination mechanism was further demonstrated by generation of chloride ions. The results suggest that surface-bound Fe(II) formed on the iron oxides surface appears to be a key factor in enhancing PCP transformation, and the mole ratio of oxalate to surface-bound Fe(II) (oxalate/Fe(II)) acted as an indicator of the enhancement effect. The enhancement mechanism attributes to strong nucleophilic ability and low reductive potential of the equivalent Fe(II)-polycarboxylate complexes. Therefore, the enhancement effects might be helpful for understanding the natural attenuation of reducible organic pollutants at the interface of contaminated soil in anoxic condition. 相似文献
An improved method for the simultaneous determination of 20 amino acids and 7 carbohydrates using one-valve switching after injection, ion chromatography, and integrated pulsed amperometric detection is proposed. The resolution of the amino acids and carbohydrates in the cation trap column was investigated. In addition, parameters including flow liquid type, flow rate, concentration, and valve-switch timing were optimized. The method is time-saving, effective, and accurate for the simultaneous separation of amino acids and carbohydrates, with a mean correlation coefficient of >0.99 and repeatability of 0.5–4.6% for eight replicates. The method was successfully applied in the analysis of amino acids and carbohydrates in aseptic media and in extracellular culture media of three phenotypes of Clostridium thermocellum. 相似文献
Well-dispersed resorcinol-formaldehyde-based carbon spheres (RFCs) have been prepared by the polycondensation of resorcinol and formaldehyde with ammonia as catalyst and subsequent carbonization of the obtained polymer. In situ polymerization of the aniline occurred in the suspension of the RFC, and RFC was surrounded by the polyaniline (PANI) wires. The PANI and RFC hybrid network (PRFC) formed gradually. In a three-electrode mode, the specific capacitance (Csp) of PRFC reaches 315 F g?1 at a current density of 1 A g?1 in 2 M H2SO4, much higher than that of pure PANI (225 F g?1) and RFC (121.7 F g?1). Furthermore, the Csp of PRFC retains 80.0 % after 1000 charge-discharge processes at a current density of 5 Ag?1. The enhanced electrochemical performance of the PRFC came from its homogeneous three-dimensional hierarchical network structure, good electric conductivity of the PANI around the RFC, and the synergistic effect between the RFC and PANI. 相似文献
Thiourea aldehyde resin-based heteroatom doping carbon and graphene composites (RHDC/GN) were prepared by an in situ polymerization and carbonization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that thiourea aldehyde resin deposited on lamellar GO flakes during the polymerization and RHDC/GN composites had a hierarchical structure. The specific capacitance of the RHDC/GN composites was high up to 355 F g?1, much higher than that of the pure thiourea aldehyde resin-based heteroatom doping carbon (RHDC) with specific capacitance of 135 F g?1 at a current density of 1.0 A g?1 in 6-M KOH electrolyte. And the hetroatoms in RHDC/GN composites increase the specific capacitance, and GN enhances the conductivity of the electrodes which is beneficial to improving electrochemical cycling stability of the electrode significantly. The specific capacitance retains 90.97% after 5000 charge-discharge processes at 10 A g?1, which provides potential as supercapacitors. 相似文献
Clay adsorbents are considered an inexpensive and readily available solution for removing heavy metals, including cadmium, from the environment to reduce pollution. In this study, thiol-modified bentonite (SH-Bent) was prepared by grafting cysteamine hydrochloride onto natural bentonite (Bent). The effects of pH, equilibrium contact time, and temperature on the adsorption–desorption behavior of Cd2+ were studied, and adsorption isotherm models were applied to examine the adsorption behavior of SH-bent. SH-Bent demonstrated better performance and stability for Cd2+ adsorption than Bent. SH-Bent exhibited an enhanced adsorption capacity for Cd2+ at equilibrium of 49.3 mg/g at pH 6, 120 min, and 303 K, which was 42-fold higher than that of Bent under the same conditions. An investigation of the desorption behavior of Cd2+ adsorbed on Bent and SH-Bent in simulated acid rain revealed that SH-Bent has high stability, with a desorption rate of 5.73% at pH 4.5, 60 min, and 303 K, which was much lower than that demonstrated by Bent under the same conditions (45.68%). The Langmuir equation was the best-fitted adsorption isotherm model, closely followed by the Freundlich, Tempkin, and Dubinin–Radushkevich models. A significant difference in diffusion was observed between the two types of clay according to the intraparticle diffusion model. The adsorption–desorption processes of SH-Bent and Bent fit the pseudo-second-order model best among the five kinetic models examined. The information provided in this study can be used to apply thiol-modified clay for wastewater treatment or for the removal of cadmium from soil.
Journal of Solid State Electrochemistry - Nitrogen and sulfur porous co-doped carbonized materials were successfully prepared from polyurethane (PU) using KOH as an activating agent with promising... 相似文献