响应面法优化鹿血肽的制备工艺

采用碱性蛋白酶水解鹿血蛋白制备鹿血肽.应用响应面分析法选取温度、时间、pH值、酶量4个主要因素,以水解率为响应值,对其工艺进行了优化.得出了鹿血蛋白水解的最佳工艺条件为:温度(53％)、时间(5.5h)、pH(9.5)、酶量(1272U·g-1),在此条件下鹿血的实际水解率为22.13％.实验证明响应面法对鹿血肽的制备...     

响应面法优化阴香籽油制备生物柴油的研究

在单因素的基础上,通过响应面法优化阴香籽油制备生物柴油的工艺条件。结果表明,阴香籽油制备生物柴油的优化工艺条件为:油醇摩尔比1∶6.5,催化剂用量为油质量的1.0%,反应时间125 min,反应温度61℃,理论转化率为92.79%。实际验证值为93.10%。以阴香籽油为原料通过酯化反应制取的生物柴油与0#柴油及国标GB/T20828—2007主要性能相似,阴香籽油生物柴油可以全部或部分替代0#柴油,是一种安全的可再生绿色生物能源。     

Electrochemical oxidation of sulfide ion at a boron-doped diamond anode

The goal of the present research was the direct conversion of sulfide, an important contaminant in geothermal brines, to sulfate, whose discharge limits are much less stringent than those for sulfide. By the use of a novel anode material boron-doped diamond (BDD), we achieved near-quantitative electrochemical conversion of sulfide ions to sulfate with current efficiency of 90%. Kinetically, the reaction is first order in current density and zero-order in sulfide concentration. The current efficiency becomes essentially quantitative in the presence of chloride ion; under these conditions the reaction is chloride-mediated, at least in part, through the electrochemical formation of hypochlorite ion. Control experiments showed that hypochlorite oxidizes sulfide to sulfate quantitatively under the same conditions.     

响应面法优化阴香籽油制备生物柴油的研究

在单因素的基础上,通过响应面法优化阴香籽油制备生物柴油的工艺条件。结果表明,阴香籽油制备生物柴油的优化工艺条件为:油醇摩尔比1∶6.5,催化剂用量为油质量的1.0%,反应时间125 min,反应温度61℃,理论转化率为92.79%。实际验证值为93.10%。以阴香籽油为原料通过酯化反应制取的生物柴油与0#柴油及国标GB/T20828—2007主要性能相似,阴香籽油生物柴油可以全部或部分替代0#柴油,是一种安全的可再生绿色生物能源。     

Response surface methodology approach to optimize coagulation-flocculation process using composite coagulants

Response surface method and experimental design were applied as alternatives to the conventional methods for optimization of the coagulation test. A central composite design was used to build models for predicting and optimizing the coagulation process. The model equations were derived using the least square method of the Minitab 16 software. In these equations, the removal efficiency of turbidity and COD were expressed as second-order functions of the coagulant dosage and coagulation pH. By applying RSM, the optimum condition using PFPD₁ was coagulant dosage of 384 mg/L and coagulation pH of 7.75. The optimum condition using PFPD₂ was coagulant dosage of 390 mg/L and coagulation pH of 7.48. Confirmation experiment demonstrated a good agreement between experimental values and model predicted. This demonstrates that RSM and CCD can be successfully applied for modeling and optimizing the coagulation process using PFPD₁ and PFPD₂.     

Mineralization of clofibric acid by electrochemical advanced oxidation processes using a boron-doped diamond anode and Fe and UVA light as catalysts

This work shows that aqueous solutions of clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid), the bioactive metabolite of various lipid-regulating drugs, up to saturation at pH 3.0 are efficiently and completely degraded by electrochemical advanced oxidation processes such as electro-Fenton and photoelectro-Fenton with Fe²⁺ and UVA light as catalysts using an undivided electrolytic cell with a boron-doped diamond (BDD) anode and an O₂-diffusion cathode able to electrogenerate H₂O₂. This is feasible in these environmentally friendly methods by the production of oxidant hydroxyl radical at the BDD surface from water oxidation and in the medium from Fenton's reaction between Fe²⁺ and electrogenerated H₂O₂. The degradation process is accelerated in photoelectro-Fenton by additional photolysis of Fe³⁺ complexes under UVA irradiation. Comparative treatments by anodic oxidation with electrogenerated H₂O₂, but without Fe²⁺, yield much slower decontamination. Chloride ion is released and totally oxidized to chlorine at the BDD surface in all treatments. The decay kinetics of clofibric acid always follows a pseudo-first-order reaction. 4-Chlorophenol, 4-chlorocatechol, hydroquinone, p-benzoquinone and 2-hydroxyisobutyric, tartronic, maleic, fumaric, formic and oxalic acids, are detected as intermediates. The ultimate product is oxalic acid, which is slowly but progressively oxidized on BDD in anodic oxidation. In electro-Fenton this acid forms Fe³⁺–oxalato complexes that can also be totally destroyed at the BDD anode, whereas in photoelectro-Fenton the mineralization rate of these complexes is enhanced by its parallel photodecarboxylation with UVA light.     

Degradation of the beta-blocker propranolol by electrochemical advanced oxidation processes based on Fenton's reaction chemistry using a boron-doped diamond anode

The electro-Fenton (EF) and photoelectro-Fenton (PEF) degradation of solutions of the beta-blocker propranolol hydrochloride with 0.5 mmol dm⁻³ Fe²⁺ at pH 3.0 has been studied using a single cell with a boron-doped diamond (BDD) anode and an air diffusion cathode (ADE) for H₂O₂ electrogeneration and a combined cell containing the above BDD/ADE pair coupled in parallel to a Pt/carbon felt (CF) cell. This naphthalene derivative can be mineralized by both methods with a BDD anode. Almost overall mineralization is attained for the PEF treatments, more rapidly with the combined system due to the generation of higher amounts of hydroxyl radical from Fenton's reaction by the continuous Fe²⁺ regeneration at the CF cathode, accelerating the oxidation of organics to Fe(III)-carboxylate complexes that are more quickly photolyzed by UVA light. The homologous EF processes are less potent giving partial mineralization. The effect of current density, pH and Fe²⁺ and drug concentrations on the oxidation power of PEF process in combined cell is examined. Propranolol decay follows a pseudo first-order reaction in most cases. Aromatic intermediates such as 1-naphthol and phthalic acid and generated carboxylic acids such as maleic, formic, oxalic and oxamic are detected and quantified by high-performance liquid chromatography. The chloride ions present in the starting solution are slowly oxidized at the BDD anode. In PEF treatments, all initial N of propranolol is completely transformed into inorganic ions, with predominance of NH₄⁺ over NO₃⁻ ion.     

Response surface methodology as a tool to study the lipase‐catalyzed synthesis of betulinic acid ester

BACKGROUND: The synthesis of betulinic acid ester using betulinic acid and oleyl alcohol catalyzed by Novozym 435 (immobilized Candida antarctica lipase) was carried out. Response surface methodology (RSM) based on a five‐level, three‐variable, central composite rotatable design (CCRD) was employed to evaluate the interactive effects of various parameters. The parameters were reaction time (8–16 h), temperature (20–60 °C) and enzyme amount (120–160 mg). RESULTS: Simultaneously increasing reaction time, temperature and amount of enzyme increased the yields of betulinic acid ester produced. CONCLUSION: The optimum conditions derived via RSM for the reaction were reaction time of 10.2 h, temperature of 53.1 °C and enzyme amount of 138 mg. The actual experimental yield was 48.5% under optimum conditions, which compared well with the maximum predicted value of 47.6%. Copyright © 2008 Society of Chemical Industry     

The improvement of boron-doped diamond anode system in electrochemical degradation of p-nitrophenol by zero-valent iron

Boron-doped diamond (BDD) electrodes are promising anode materials in electrochemical treatment of wastewaters containing bio-refractory organic compounds due to their strong oxidation capability and remarkable corrosion stability. In order to further improve the performance of BDD anode system, electrochemical degradation of p-nitrophenol were initially investigated at the BDD anode in the presence of zero-valent iron (ZVI). The results showed that under acidic condition, the performance of BDD anode system containing zero-valent iron (BDD-ZVI system) could be improved with the joint actions of electrochemical oxidation at the BDD anode (39.1%), Fenton's reaction (28.5%), oxidation–reduction at zero-valent iron (17.8%) and coagulation of iron hydroxides (14.6%). Moreover, it was found that under alkaline condition the performance of BDD-ZVI system was significantly enhanced, mainly due to the accelerated release of Fe(II) ions from ZVI and the enhanced oxidation of Fe(II) ions. The dissolved oxygen concentration was significantly reduced by reduction at the cathode, and consequently zero-valent iron corroded to Fe(II) ions in anaerobic highly alkaline environments. Furthermore, the oxidation of released Fe(II) ions to Fe(III) ions and high-valent iron species (e.g., FeO²⁺, FeO₄²⁻) was enhanced by direct electrochemical oxidation at BDD anode.     

Investigations of electrochemical oxygen transfer reaction on boron-doped diamond electrodes

In this paper, the electrochemical oxygen transfer reaction (EOTR) is studied on boron-doped diamond electrodes using simple C₁ organic compounds (methanol and formic acid). The kinetics of both oxygen evolution (side reaction) and organics oxidation (main reaction) has been investigated using boron-doped diamond microelectrodes-array (BDD MEA). Oxygen evolution, in the high-potential region, takes place with a Tafel slope of 120 mV dec⁻¹ and zero reaction order with respect to H⁺. In the presence of organics, a shift of the polarization curves to lower potentials is observed while the Tafel slopes remain close to 120 mV dec⁻¹. A simplified model of C₁ organics oxidation is proposed. Both water discharge and organics oxidation are assumed to be fast reactions. The slowest step of the studied EOTR is the anodic discharge of hydroxyl radicals to oxygen. Further in this work, electrolysis of formic acid on boron-doped diamond macroelectrode is presented. In order to achieve 100% current efficiency, electrolysis was carried out under programmed current, in which the current density was adjusted to the limiting value.     

Electrochemical incineration of dyes using a boron‐doped diamond anode

The electrochemical oxidation of a synthetic wastewater containing the model dyes alizarin red (an anthraquinone) and Eriochrome black T (an azoic compound) has been studied on a boron‐doped diamond electrode (BDD) by both cyclic voltammetry and bulk electrolysis. The influence of the current density and dye concentration were investigated. The results obtained show that complete chemical oxygen demand (COD) and colour removal was obtained for both wastewaters. However, the nature of the pollutant, and specially the presence of functional groups (such as the azoic group) seems to strongly influence the performance and efficiency of the electrochemical process. The electro‐oxidation of alizarin red behaves as a mass‐transfer‐controlled process. In such a system, an increase in the current density leads to a decrease in the current efficiency. This can be explained by direct or hydroxyl radical mediated oxidation. The contrary tendency has been observed in Eriochrome black T electro‐oxidation. In this case, higher efficiencies were obtained working at high current densities. This may indicate that the mediated oxidation by electrogenerated reagent (such as peroxodisulphate) is the main oxidation mechanism involved in Eriochrome black T treatment. These compounds have a longer average lifetime than hydroxyl radicals, and it allows the reaction to be extended to the whole wastewater volume. This study has shown the suitability of the electrochemical process for completely removing the COD and total organic carbon and effectively decolourising of wastewaters containing synthetic dyes. Copyright © 2007 Society of Chemical Industry     

Efficient electrochemical decomposition of perfluorocarboxylic acids by the use of a boron-doped diamond electrode

The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant (k₁) of 2.4 × 10^− 2 dm³ h^− 1. Under the present reaction conditions, k₁ increased with increasing current density and saturated at values over 0.60 mA cm^− 2. Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C-C bond between the C₇F₁₅ and COOH in PFOA and generates a C₇F₁₅ radical and CO₂. The C₇F₁₅ radical forms the thermally unstable alcohol C₇F₁₅OH, which undergoes F⁻ elimination to form C₆F₁₃COF. This acid fluoride undergoes hydrolysis to yield another F⁻ and the perfluorocarboxylic acid with one less CF₂ unit, C₆F₁₃COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO₂ and F⁻. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface.     

Heat transfer resistance as a tool to quantify hybridization efficiency of DNA on a nanocrystalline diamond surface

In this article, we report on a label-free real-time method based on heat transfer resistivity for thermal monitoring of DNA denaturation and its potential to quantify DNA fragments with a specific sequence of interest. Probe DNA, consisting of a 36-mer fragment was covalently immobilized on a nanocrystalline diamond surface, created by chemical vapor deposition on a silicon substrate. Various concentrations of full matched 29-mer target DNA fragments were hybridized with this probe DNA. We observed that the change in heat transfer resistance upon denaturation depends on the concentration of target DNA used during the hybridization, which allowed us to determine the dose–response curve. Therefore, these results illustrate the potential of this technique to quantify the concentration of a specific DNA fragment and to quantify the hybridization efficiency to its probe.     

Response surface methodology to optimize enzymatic preparation of deapio-platycodin d and platycodin d from radix platycodi

In the present work, we reported the enzymatic preparation of deapio-platycodin D (dPD) and platycodin D (PD) optimized by response surface methodology (RSM) from Radix Platycodi. During investigation of the hydrolysis of crude platycosides by various glycoside hydrolases, snailase showed a strong ability to transform deapio-platycoside E (dPE) and platycoside E (PE) into dPD and PD with 100% conversion. RSM was used to optimize the effects of the reaction temperature (35-45 °C), enzyme load (5-20%), and reaction time (4-24 h) on the conversion process. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of dPD and PD conversion yield. The optimum preparation conditions were as follows: temperature, 43 °C; enzyme load, 15%; reaction time, 22 h. The biotransformation pathways were dPE→dPD3→dPD and PE→PD3→PD, respectively. The determined method may be highly applicable for the enzymatic preparation of dPD and PD for medicinal purposes and also for commercial use.     

Novel application of boron-doped diamond and related material to electrochemical generation of functional water

The performances of the electrogeneration of ClO⁻ on the different electrode materials, such as boron-doped diamond (BDD), Pt/BDD and Pt, were investigated at constant voltages of 10, 20 and 30 V as well as constant currents of 25, 50 and 75 mA. The BDD and Pt/BDD electrodes showed superior to platinum electrode for the ClO⁻ generation at both constant voltage and constant current conditions under respective room temperature (RT) and low temperature (LT) (2-5 °C). Both BDD and Pt/BDD electrodes exhibited high stability used under high voltage and current conditions.     

Effect of electronic structures on electrochemical behaviors of surface-terminated boron-doped diamond film electrodes

In order to analyze the electrochemical behaviors of hydrogen-terminated and oxygen-terminated boron-doped diamond film electrodes, experiments of the cyclic voltammetry and AC impedance spectroscopy have been performed. For the purpose of clarifying the detailed electronic structures of these diamond films, current–voltage spectroscopy curves and XPS spectra have been investigated by scanning probe microscopy and X-ray photoelectron spectroscopy, respectively. For the hydrogen-terminated boron-doped diamond film electrode, its potential window is narrower than that of the oxygen-terminated boron-doped diamond. The impedance results indicate that the diamond film resistances and capacitances corresponding to different surface-terminated boron-doped diamond electrodes vary significantly. The surface band gap of hydrogen-terminated diamond film is narrow with empty surface states in it. In contrast, the surface band gap of oxygen-terminated diamond film is wide and clean. Compared with hydrogen-terminated diamond film, the surface energy bands of oxygen-terminated diamond film bend downwards. Based on their electronic structures, the electrochemical behaviors of the two boron-doped diamond film electrodes have been discussed.     

掺硼金刚石阳极电催化降解新兴抗生素类污染物研究进展

抗生素类药物是目前水环境中出现的一类新兴有机污染物,具有难自然降解、环境刺激性、生物毒性及耐药性等特点,高效去除抗生素类污染物是近年来环境工作者重点探讨的内容。掺硼金刚石（boron-doped diamond,BDD）电极由于自身优异的物理和化学性质,被认作为目前电催化氧化水中有机污染物最为理想高效的阳极材料,但关于BDD阳极在新兴抗生素类污染物的研究情况尚未进行及时的总结。本文首先论述了BDD阳极在电催化氧化有机污染物的降解过程和基于强氧化性物种的电催化氧化机理,进而分析了BDD阳极在电催化降解水中新兴抗生素类污染物的研究进展,探讨了影响抗生素类污染物电催化降解过程的关键影响因素,总结了BDD阳极材料的开发情况,同时,总结了以BDD阳极电催化氧化为基础发展而来的其他水处理联合方法,最后,进一步展望了BDD阳极在未来电催化降解抗生素类污染物存在的问题及未来的重点发展方向。     

Response surface methodology study on electrochemical adsorption regeneration of water-based drilling fluid waste

ABSTRACT

This study explores an electrochemical adsorption method on the regeneration of aqueous drilling fluid waste. Response surface analysis was applied to investigating the electrochemical factors on the adsorption performance. The response surface polynomial model optimized the preferred electrochemical adsorption conditions with adsorption time of 20 min, spacing electrodes of 5 cm, adsorption concentration of 5% and NaCl concentration of 2 g/L. The model calculated electrochemical adsorption amount of drilling fluid showed only 1.3% deviation from the experimental results. Thus, the model could provide effective support for the device design and application of drilling fluid electrochemical adsorption process.     

On the changing electrochemical behaviour of boron-doped diamond surfaces with time after cathodic pre-treatments

The electrochemical response of the Fe(CN)₆^4−/3− redox couple on boron-doped diamond (BDD) electrodes immediately after a cathodic pre-treatment and as a function of time exposed to atmospheric conditions is reported here. After this pre-treatment the electrode exhibits a changing electrochemical behaviour, i.e., a loss of the reversibility for the Fe(CN)₆^4−/3− redox couple as a function of time. Raman spectra showed that neither important bulk structural differences nor significant changes in the sp²/sp³ content are introduced into the BDD film by the cathodic pre-treatment indicating that H-terminated sites play an important role in the electrochemical response of the electrodes. Thus, the changing behaviour reflected by a progressive decrease of the electron transfer rate with time must be associated to a loss of superficial hydrogen due to oxidation by oxygen from the air, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Moreover, it was also found that this changing electrochemical behaviour is inversely proportional to the doping level, suggesting that the boron content has a stabilizing effect on the H-terminated surface. These results point out the necessity of doing the cathodic pre-treatment just before the electrochemical experiments are carried out in order to ensure reliable and reproducible results.