External Catalyst- and Additive-Free Photo-Oxidation of Aromatic Alcohols to Carboxylic Acids or Ketones Using Air/O2.

We present an environment-friendly and highly efficient method for the oxidation of aromatic alcohols to carboxylic acids or ketones in air via light irradiation under external catalyst-, additive-, and base-free conditions. The photoreaction system exhibits a wide substrate scope and the potential for large-scale applications. Most of the desired products are easily obtained via recrystallization and separation from low-boiling reaction medium acetone in good yields, and the products can be subsequent directly transformed without further purification.

Effect of iron ion configurations on Ni2+ removal in electrocoagulation.

Electrocoagulation (EC) has been widely used to treat the heavy metal wastewater in industry. A novel process of sinusoidal alternating current electrocoagulation (SACC) is adopted to remove Ni2+ in wastewater in this study. The morphology of precipitates and the distribution of the main functional iron configurations were investigated. Ferron timed complex spectroscopy can identify the monomeric iron configurations [Fe(a)], oligomeric iron configurations [Fe(b)] and polymeric iron configurations [Fe(c)]. The optimal operating conditions of SACC process were determined through single-factor experiments. The maximum Ni2+ removal efficiency [Re(Ni2+)] was achieved under the conditions of pH0=7, current density (j) = 7 A/m2, electrolysis time (t) = 25 min, c0(Ni2+) = 100 mg/L. At pH=7, the proportion of Fe(b) and Fe(c) in the system was 50.4 at.% and 23.1 at.%, respectively. In the SACC process, Fe(b) and Fe(c) are the main iron configurations in solution, while Fe(c) are the vast majority of the iron configurations in the direct current electrocoagulation (DCC) process. Re(Ni2+) is 99.56% for SACC and 98.75% for DCC under the same optimum conditions, respectively. The precipitates produced by SACC have a high proportion of Fe(b) configurations with spherical α-FeOOH and γ-FeOOH structures which contain abundant hydroxyl groups. Moreover, it is demonstrated that Fe(b) has better adsorption capacity than Fe(c) through adsorption experiments of methyl orange (MO) dye. Fe(a) configurations in the homogeneous solution had no effect on the removal of nickel.

1,2-Dibutoxyethane-Promoted Oxidative Cleavage of Olefins into Carboxylic Acids Using O2 Under Clean Conditions.

Herein, we report the first example of an effective and green approach for the oxidative cleavage of olefins to carboxylic acids using a 1,2-dibutoxyethane/O2 system under clean conditions. This novel oxidation system also has excellent functional-group tolerance and is applicable for large-scale synthesis. The target products were prepared in good to excellent yields by a one-pot sequential transformation without an external initiator, catalyst, and additive.

Comparison between sinusoidal AC coagulation and conventional DC coagulation in removing Cu2+ from printed circuit board wastewater.

A new Electrocoagulation (EC) technique, sinusoidal AC coagulation (SACC), is creatively put forward for Cu2+ removal in the wastewater from the printed circuit board (PCB) production in this paper. The removal efficiency of Cu2+ from PCB wastewater and energy consumption are compared by SACC and conventional direct current coagulation (DCC). The optimal process parameters were established through analysis of response surface methodology (RSM). The coagulations containing Cu2+ was characterized by SEM, EDS, TEM，BET, XRD and FTIR. The nano-ferrum collosol, mainly composed of goethite (α-FeOOH) and magnetite (γ-Fe2O3), absorbs the Cu2+ and coagulates to remove Cu2+. The results show that the removal rates of Cu2+ by SACC and DCC are 99.86％ and 98.21％, respectively, and the energy consumption is 2.76 × 10-2 kWh⋅m-3 for SACC and 4.42 × 10-2 kWh⋅m-3 for DCC under the optimal process conditions of c0 (Cu2+) = 41.99 mg⋅dm-3, pH = 7.14, j = 0.293 A⋅m-2, t = 16.7 min. The pilot tests indicate that the SACC technique is feasible in industrial application. Cu2+ removal were completed through electrodeposition of Cu2+ on iron electrode, the deposition of Cu(OH)2 and the adsorption of Cu2+ by ferrum collosol. The adsorption follows the pseudo-second order kinetics model well. The maximum saturated adsorption capacity (qmax) of Cu2+ on ferrum collosol produced by SACC is larger than that by DCC. The adsorption of Cu2+ on the ferrum collosol prepared by SACC and DCC are in accordance with Langmuir's adsorption isotherms. The novel SACC technique is a promising technique for the highly-efficient treatment of Cu2+ from PCB wastewater.

Treatment of Zn2+ in wastewater by sinusoidal alternating current coagulation: response surface methodology and removal mechanism.

A novel sinusoidal alternating current coagulation (SACC) technique was used to remove the Zn2+ from wastewater in the present study. The response surface methodology was used to analyze the effect of current density, time, initial pH and initial Zn2+ concentration in order to obtain the optimum removal efficiency and to lower energy consumption. The results show that SACC with a current density of 0.31 A·m-2 applied to treat wastewater containing 120 mg·dm-3 Zn2+ at pH = 9 for 21.3 min can achieve a removal efficiency of Zn2+ of 98.80%, and the energy consumption is 1.147 kWh·m-3. The main component of flocs produced in SACC process is Fe5O7OH·4H2O (HFO). Large specific surface area and good adsorption performance of HFO are demonstrated. There is strong interaction between Zn2+ and HFO. Zn2+ is adsorbed and trapped by HFO and then co-precipitated. Freundlich adsorption isotherm model and pseudo-second order kinetics model explained the Zn2+ adsorption behavior well. The Zn2+ adsorption on HFO is an endothermic and spontaneous process.

Study on highly efficient Cr(VI) removal from wastewater by sinusoidal alternating current coagulation.

Cr(IV) pollution in water leads to serious environmental contamination and health risks. Among various wastewater treating methods, electrocoagulation (EC) is widely applied because of its high efficiency. However, there is still a problem of high energy consumption that has to be solved by direct current coagulation (DCC). In this paper, a sinusoidal alternating current coagulation (SACC) technique was used to reduce energy consumption and improve the efficiency of Cr(VI) removal. The effects of pH value, current density, initial concentration of Cr(VI) and reaction time are studied on the removal of Cr(VI). The response surface methodology (RSM) was used to optimize the parameters of SACC process. Compared with pulse direct current coagulation (PDCC) and DCC, SACC can greatly reduce the concentration polarization and prevent Fe electrodes from passivation so as to reduce energy consumption and improve the efficiency of Cr(VI) removal. When pH 5.6 wastewater containing 33.1 mg⋅dm-3 Cr(VI) was treated by applying 2.7 A⋅m-2 density for 20.5 min, the removal rate of Cr(VI) reached 99.73%, and the residual Cr(VI) in the effluent was <0.1 mg⋅dm-3. The power consumption of SACC process decreases by 14.98% compared to DCC process and the electrode loss is about 16.4% less than that of the DCC. The coagulation produced by SACC has a large specific surface area and better adsorption performance through analysis of SEM and EDS as well as adsorption dynamic analysis. FTIR and XRD patterns verified the strong interaction between Cr(VI) and iron sol. The Cr(VI) on the electrode can be deposited as a form of insoluble Cr(III) compounds. Langmuir adsorption isotherm model and the second-order kinetic model in SACC are more suitable to explain the adsorption behavior and characteristics of Cr(VI) in SACC.

Fluorescent Porous Carbazole-Decorated Copolymer Monodisperse Microspheres: Facile synthesis, Selective and Recyclable Detection of Iron†(III) in Aqueous Medium.

We demonstrate an environmentally friendly one-step soap-free emulsion polymerization strategy to develop fluorescent carbazole-based copolymer monodisperse microspheres for highly sensitive and selective detection of Fe3+ . The copolymer microspheres feature a stable spherical morphology with a narrow size distribution through regulating N-vinylcarbazole (NVCz) content (1.25-10.0 wt.%). Notably, the as-made microspheres exhibit a strong luminescence, tunable emission intensity and specific surface areas. Interestingly, the fluorescence of the copolymer microspheres can be selectively quenched by trace amounts of Fe3+ due to the oxidation of carbazole, and the quenching fluorescence can be facilely recovered by reduction with NaBH4 . Its excellent sensing performance is shown in terms of high sensitivity (low limit of detection, 1.3 µm), excellent selectivity, and rapid response rate, due to the porous nature of the copolymer microspheres. These results illustrate the copolymer microspheres obtained by simple preparative procedure without using expensive or toxic raw materials would serve as a high performance sensor for highly selective and recyclable detection of Fe3+ in aqueous medium.

Influence of the AC field intensity and frequency on composition and growth mechanism of Au-Pd alloy nanowires.

Au-Pd alloy nanowires with controllable morphology and composition are useful sensing materials for chemical and biological sensors. This report describes the preparation of such Au-Pd alloy nanowires from an aqueous solution by alternating current (AC) varied-frequency method, focusing on determining the dependence of the composition and morphology of the alloy nanowires on the electric field intensity and frequency. An electric field varied from 0.1 V x m(-1) to 0.4 x 10(6)V x m(-1) at 300 Hz frequency was used for the nucleation, followed by variation of the frequency between 1 and 20 MHz for the growth of the nanowires. The results showed that the Pd content in the alloy nanowires increased with the field intensity and frequency. The nanowire morphology with a less branching and better alignment was obtained at the increased frequency. XRD results showed that the phase structure of the alloy nanowires was face-centered cubic lattice. The nanowire compositions were shown controllable by changing the AC field intensity, frequency, as well as the metal ion ratio in the solution. The growth of the nanowires was shown to obey the Maxwell-Wanger (M-W) law.

Study on removal of phosphorus and COD in wastewater by sinusoidal AC Fenton oxidation-coagulation.

In order to treat domestic wastewater containing phosphorus and chemical oxygen demand (COD), the new technology of Sinusoidal Alternating Current (AC) Fenton Oxidation-Coagulation (SACFOC) was used to improve the removal efficiency (Re) and reduce energy consumption (EEC). The morphology, elemental composition, crystal structure and functional groups of the sludge were characterised by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The results show that total phosphorus removal efficiency {Re(TP)} and removal efficiency of organic matter {Re(COD)} can reach 97.56% and 87.77%, respectively, but EEC is only 0.09 kWh·m-3 under the optimum conditions of pH0 = 3, current density (j) = 0.5 A·m-2, c0(TP) = 18 mg·dm-3, c0(COD) = 300 mg·dm-3, c0(H2O2) = 0.06 mol·dm-3, t = 45 min. As compared with direct current (DC) Fenton Oxidation-Coagulation (DCFOC), the COD removal efficiency of SACFOC treatment was improved by 37%, but the energy consumption was reduced by 45%. The degradation process of total phosphorus and COD by SACFOC abides by the quasi-first-order kinetic model. The process of SACFOC includes double effects of electrocoagulation of iron sol by electrolysis and degrade COD by oxidation of formed hydroxyl radicals (·OH) in wastewater, which improves removal efficiency of total phosphorus and COD in wastewater. Our research findings will provide technical guidance and a theoretical basis for the simultaneous treatment of wastewater containing phosphorus and COD applying SACFOC process.

Removal of phosphorus in wastewater by sinusoidal alternating current coagulation: performance and mechanism.

The effects of initial total phosphorus (TP) concentration, current density, conductivity and initial pH value on the removal rate of TP and energy consumption, as well as the behaviour and mechanism of phosphorus removal, were investigated by sinusoidal alternating current coagulation (SACC). The flocs produced by SACC were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy FTIR and X-ray photo electron spectroscopy. The thermodynamic and kinetic behaviours of phosphorus removal by iron sol adsorption were also studied in detail. In a self-made SACC reactor equipped with five sets of parallel iron electrodes spacing 10 mm, the removal rate of TP reached 90.9% for a pH 7.0 wastewater with 5 mg dm-3 TP (κ = 800 µS cm-1) after being treated for 60 min by applying 2.12 mA cm-2 sinusoidal alternating current. Compared with direct current coagulation (DCC), SACC exhibits a higher removal efficiency of phosphorus due to the stronger adsorption of the produced flocs. It was found that the adsorption in the SACC process follows pseudo-second-order kinetic with the involvement of the intra-particle model. The adsorption of iron sol to phosphorus was an endothermic and spontaneous process, and its adsorption behaviour can be characterized with Langmuir and Redlich-Peterson isothermal adsorption models. SACC may be employed for the treatment of more complex wastewater combined with biological and/or electrochemical techniques.

Study on the treatment of Cu2+-organic compound wastewater by electro-Fenton coupled pulsed AC coagulation.

Electro-Fenton (EF) coupled with Pulsed alternating current coagulation (PACC) is an effective technology for the treatment of Cu2+-organic wastewater. In this study, the removal efficiency (Re), electrical energy consumption (EEC) and removal mechanism of Cu2+-organic were analyzed and the optimal operation parameters were determined. SEM, EDS, XRD and FTIR were used to characterize the morphology, elemental composition, crystal structure, function groups of sludge produced in the EF-PACC. UV, ESR and GC-MS were employed to determine concentration of organic matter, existence of OH, middle products of decomposed organic matter in EF-PACC, respectively. The results show that under the optimal conditions of initial pH = 2.5, current density (j) = 2 A/m2, initial c(Cu2+) = 50 mg/L, c(chemical oxygen demand, COD) = 500 mg/L, c[H2O2] = 10 mL/L, frequency (f) = 1 Hz, t = 20 min, the Re(Cu2+) can reach 99.59%. Re(COD) is 90.21%, EEC 1.695 × 10-1 kWh/m3, and the amount of produced sludge (Ws) is 0.9283 kg/m3. Compared with single EF and PACC processes, the order of treatment efficiency is EF-PACC > EF > PACC. EF-PACC technique was a highly effective method in the treatment of Cu2+-organic compound wastewater. The EF-PACC coupled process includes that electrolyzed Fe3+ produces electrocoagulation and OH produces degradation of organic compounds. The combined action of the two effects can effectively remove Cu2+-organic from wastewater.

A novel technique of COD removal from electroplating wastewater by Fenton-alternating current electrocoagulation.

The present study employs a novel technique combining Fenton reaction with sinusoidal alternating current electrocoagulation (FSACEC), which is used to remove chemical oxygen demand (COD) in the simulated electroplating wastewater with the advantages of low energy consumption and small sludge. Fe2+, produced from the dissolution of Fe anodes in the FSACEC process, reacts with H2O2 to generate more ·OH and forms the iron hydroxide precipitates. The higher efficiency of COD removal is achieved through both effects of the oxidation reaction and the physical adsorption. The scanning electron microscopy (SEM) analysis shows that the particle size of FSACEC products is between 30 and 40 nm, which is less than the Fenton-direct current electrocoagulation products. The effect of the current concentration (IV), initial pH (pH0), and the addition of hydrogen peroxide (30% H2O2) was discussed on the optimal process parameters. In pH0 2.0 wastewater, applying current concentration of 1 A dm-3, the addition 20 cm3 dm-3 30% H2O2, the removal efficiency of COD reached 94.21% and the residual COD in wastewater was only 60 mg dm-3 after 90 min of operation. In order to investigate the maximum removal efficiency in a certain period of operation, the larger current concentration is applied to remove COD. The FSACEC process exhibits the higher removal COD efficiency and wider operation range of pH0 than the single Fenton technique. The FSACEC process is in accordance with the kinetic law of the pseudo-second-order kinetic adsorption model.

Gold-platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide.

The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold-platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.