Electrochemical degradation of tramadol hydrochloride: Novel use of potentiometric carbon paste electrodes as a tracer

The electrochemical removal of tramadol hydrochloride from aqueous solutions has been investigated under several operating conditions using a Pb/PbO₂ electrode. The optimum conditions of the treatment process are: current density of 1000 mA/cm⁻², pH ≈6, temperature of 10 °C and initial tramadol hydrochloride concentration of 100 mg/L. The time of electrolysis is 25 min for degradation rate of tramadol hydrochloride and chemical oxygen demeaned (COD) removal is 22 h. The results were obtained by UV–Vis spectrophotometer and the presently designed electrode was coincident.     

Preparation of quaternized dimethylaminoethylmethacrylate grafted nonwoven fabric for the removal of phosphate

Dimethylaminoethylmethacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fabric was prepared by radiation-induced graft polymerization. Grafting conditions were optimized and about 150% DMAEMA grafted samples were used for further experiments. DMAEMA graft chains were later quaternized with dimethyl sulphate for the removal of phosphate ions. Adsorption experiments were conducted with quaternized DMAEMA grafted fabric for phosphate removal at low (0.5–25 ppm) and high phosphate concentrations (50–1000 ppm). Adsorbed phosphate amounts at pH 7 were found to be 63 mg phosphate/g polymer and 512 mg phosphate/g polymer for low (25 ppm) and high phosphate concentrations (1000 ppm) respectively showing the efficiency of the adsorbent material in removing phosphate. The pH effect on phosphate adsorption showed that the quaternized DMAEMA grafted nonwoven fabric can adsorb phosphate over a wide pH range (5.00–9.00) indicating that adsorbent material can effectively remove different forms of phosphate ions, namely H₂PO₄^?, HPO₄^2? and PO₄^3? in aqueous solution at this pH range where the species exist. Competitive adsorption experiments were also carried out with two concentration levels at pH 7 to investigate the effect of competing ions. Phosphate adsorption on quaternized DMAEMA grafted nonwoven fabric was found to be higher than the other competing ions at two concentration levels. At high concentration level, the adsorption order was phosphate>nitrite>bromide>sulphate>nitrate whereas at low concentration level, the order was phosphate?sulphate>bromide>nitrite>nitrate.     

Amperometric determination of chemical oxygen demand using boron-doped diamond (BDD) sensor

A new application of boron-doped diamond (BDD) electrode was developed for detecting chemical oxygen demand (COD) by amperometric method. The effects of some basic experimental parameters including pH and applied potential on the response of the BDD electrode were investigated and the optimal operating conditions were obtained. In the COD tests of standard samples, a wide linear range of 20–9000 mg l⁻¹ COD and a low detection limit of 7.5 mg l⁻¹ COD were well established with the present approach. Additionally, the BDD sensor was successfully employed to determine the COD of real samples from various chemical or pharmaceutical wastewaters and the performance still kept stable after over 400 measurements. The results obtained indicated that, as compared with the conventional COD determination techniques, the proposed sensor was an environmentally friendly method with the advantages of short analysis period, simplicity, and no requirement of complicated sample pretreatment even for a sample containing relatively high concentration of organic pollutants.     

Novel metal-based pharmacologically dynamic agents of transition metal(II) complexes: Designing,synthesis, structural elucidation,DNA binding and photo-induced DNA cleavage activity

Novel Schiff base Cu(II), Ni(II), Co(II) and Zn(II) complexes have been designed and synthesized using the macrocyclic ligand derived from the condensation of diethylphthalate with Schiff base, obtained from benzene-1,2-diamine and 3-benzylidene-pentane-2,4-dione. The ligand and its complexes have been characterized by analytical and spectral techniques. DNA binding properties of these complexes have been investigated by UV–vis, viscosity measurements, cyclic voltammetric and differential pulse voltammogram studies. The intrinsic binding constants for Co(II), Ni(II), Cu(II) and Zn(II) complexes are 1.6 × 10⁶, 1.8 × 10⁶, 2.0 × 10⁶ and 1.5 × 10⁶ M^?1 respectively which are obtained from electronic absorption experiment. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder (distamycin) suggest the major groove binding tendency for the synthesized complexes. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), the synthesized complexes show chemical nuclease activity under dark reaction condition. The complexes also show efficient photo-induced DNA cleavage activity on irradiation with a monochromatic UV light of 360 nm in the presence of inhibitors. Control experiments show inhibition of cleavage in the presence of singlet oxygen quencher like sodium azide and enhancement of cleavage in D₂O, suggesting the formation of singlet oxygen as a reactive species in a type-II process.     

Treatment of opium alkaloid containing wastewater in sequencing batch reactor (SBR)—Effect of gamma irradiation

Aerobic biological treatment of opium alkaloid containing wastewater as well as the effect of gamma irradiation as pre-treatment was investigated. Biodegradability of raw wastewater was assessed in aerobic batch reactors and was found highly biodegradable (83–90% degradation). The effect of irradiation (40 and 140 kGy) on biodegradability was also evaluated in terms of BOD₅/COD values and results revealed that irradiation imparted no further enhancement in the biodegradability. Despite the highly biodegradable nature of wastewater, further experiments in sequencing batch reactors (SBR) revealed that the treatment operation was not possible due to sludge settleability problem observed beyond an influent COD value of 2000 mg dm^?3. Possible reasons for this problem were investigated, and the high molecular weight, large size and aromatic structure of the organic pollutants present in wastewater was thought to contribute to poor settleability. Initial efforts to solve this problem by modifying the operational conditions, such as SRT reduction, failed. However, further operational modifications including addition of phosphate buffer cured the settleability problem and influent COD was increased up to 5000 mg dm^?3. Significant COD removal efficiencies (>70%) were obtained in both SBRs fed with original and irradiated wastewaters (by 40 kGy). However, pre-irradiated wastewater provided complete thebain removal and a better settling sludge, which was thought due to degradation of complex structure by radiation application. Degradation of the structure was observed by GC/MS analyses and enhancement in filterability tests.     

The preparation of an adsorbent from mixtures of sewage sludge and coal-tar pitch using an alkaline hydroxide activation agent

The increasing generation of sewage sludge and its subsequent treatment are very sensitive environmental problems. For the more stable and sanitary treatment of this sewage sludge, there have been many studies, including the recent attempt to prepare an adsorbent from sewage sludge via recycling. In this study, of the adsorbent preparation methods, chemical activation was utilized, and in order to find the optimum conditions, several variables were tested, such as the activation agent concentration, activation temperature and activation time. The activation agents used in this study were alkaline hydroxides: KOH and NaOH. The properties of prepared adsorbent were also measured by analyzing the iodine adsorptivity and surface area. In addition, the prepared adsorbent, the BOD, COD, SS, T-N and T-P removal efficiencies from the effluent water of a sewage treatment plant were examined via column test. From the test, the optimum conditions for KOH-activation were 1 mol/l, 800 °C and 1.5 h for the activation agent concentration, activation temperature and activation time, respectively; whereas those for NaOH-activation were 1.25 mol/l, 850 °C and 1.5 h. From the application of the prepared adsorbent to the effluent water of the sewage treatment plant, the measured BOD, COD, SS, T-N and T-P removal efficiencies, the P1-800 adsorbent had the highest efficiencies for BOD, COD and SS of 56.68, 57.76 and 81.45%, respectively.     

Wagner liquid–vapour pressure equation constants from a simple methodology

A methodology to determine the A, B, C, and D constants from the Wagner equation is presented. The constants for 274 pure substances were determined by minimization in the sum of the squares of the relative deviation in liquid vapour pressure. For 69 chemical compounds, vapour pressures exist over the range from 1 kPa to the critical pressure and an average absolute deviation in vapour pressure of 0.039% was calculated. Using Antoine equation coefficients and initial guesses for a correlation in terms of the acentric factor, Wagner constants were estimated for substances with limited data within the range from (1 to 200) kPa. To validate the proposed methodology, vapour pressure predictions from 1 kPa to the critical pressure were made for 52 substances using Wagner parameters estimated from limited data. A value of 0.27% in average absolute deviation results for those substances. Finally the Waring criterion was applied to check the constants presented in this paper.     

Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation

Pharmaceuticals in wastewater were treated by the combined method of activated sludge and ionizing radiation in laboratory scale. Oseltamivir, aspirin, and ibuprofen at 5 μmol dm^?3 in wastewater were decomposed by the activated sludge at reaction time for 4 h. Carbamazepine, ketoprofen, mefenamic acid, clofibric acid, and diclofenac were not biodegraded completely, but were eliminated by γ-ray irradiation at 2 kGy. The rate constants of the reactions of these pharmaceuticals with hydroxyl radicals were estimated by the competition reaction method to be 4.0–10×10⁹ mol^?1 dm³ s^?1. Decompositions of the pharmaceuticals in wastewater by ionizing radiation were simulated by use of the rate constants and the amount of total organic carbon as parameters. Simulation curves of concentrations of these pharmaceuticals as a function of dose described the experimental data, and the required dose for the elimination of them in wastewater by ionizing radiation can be estimated by this simulation.     

Electrokinetic pumping system based on nanochannel membrane for liquid delivery

Nonmechanical pumping of liquids is of key importance for applications from the biomedical microfluidic chip to drug delivery systems. In this paper, a new electrokinetic pump (EOP) system with polycarbonate nanochannel membrane sandwiched between two membrane holders was constructed. The pump was tested with water and phosphate buffer at 1-6 V applied voltage, the maximum pressure and flow rate are 0.32 MPa (3.2 atm) and 4.2 mL/min for phosphate buffer, respectively. This proof-of-concept pump shows its potential use for drugs or chemical agents delivery by the usage of different membrane materials.     

Chemical characteristics of aerosol insecticide deposition in indoor surfaces

We investigated the deposition rate of aerosol insecticide on through woollen surfaces inside a test chamber. Compared to floor surface, the deposition rate of aerosol insecticide active ingredient on table of 1 m high was up to 2.07 times for piperonyl butoxide, 1.64 times for tetramethrin and 2.95 times for permethrin represented by 0.51, 0.37 and 0.23 μg cm^?2 for the three molecules, respectively. Application of the household used cleaning to the woollen table surface decrease these concentrations by 61.32%, 45.01% and 59.80% for the three pesticides respectively, this cleaning procedure still not efficient for the floor surfaces. Moreover, indoor conditions permit the removal of 46.42%, 21.92% and 14.35% of the table surface deposition rate after one week, for the three pesticides, respectively. These conditions ensure the removal of only 28.72%, 20.69% and 24.05% of the three deposit molecules respectively on floor surface.     

Gamma radiation induced effects on slaughterhouse wastewater treatment

A preliminary study using gamma radiation on slaughterhouse wastewater samples was carried out. Chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) results were obtained at a dose rate of 0.9 kGy h⁻¹. A decrease of COD, BOD and colour was observed after irradiation at high absorbed doses. The microbiological results, following irradiation in the same conditions, correlated with the BOD results. The results obtained highlight the potential of this technology for wastewater treatment.     

Determination of formal potential of NADH/NAD+ redox couple and catalytic oxidation of NADH using poly(phenosafranin)-modified carbon electrodes

The electrochemical regeneration of NADH/NAD⁺ redox couple has been studied using poly(phenosafranin) (PPS)-modified carbon electrodes to evaluate the formal potential and catalytic rate constant for the oxidation of NADH. The PPS-modified electrodes were prepared by electropolymerization of phenosafranin onto different carbon substrates (glassy carbon (GC) and basal-plane pyrolytic graphite (BPPG)) in different electrolytic solutions. The formal potential was estimated to be ? 0.365 ± 0.002 V vs. SHE at pH 7.0. As for the bare carbon electrodes, the oxidation of NADH at the BPPG electrode was found to be enhanced compared with the GC electrode. For the PPS-modified electrodes, it was found that the electrocatalysis of PPS-modified electrodes for the oxidation of NADH largely depends on the carbon substrate and electrolyte solution employed for their preparation, i.e., the PPS-modified BPPG electrode prepared in 0.2 M NaClO₄/acetonitrile solution exhibits an excellent and persistent electrocatalytic property toward NADH oxidation in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 740 and 670 mV compared with those at the bare GC electrode and the PPS-modified GC electrode prepared in 0.2 M H₂SO₄ solution, respectively. A quantitative analysis of the electrocatalytic reaction based on rotating disk voltammetry gave the electrocatalytic reaction rate constants of the order of 10³–10⁴ M^?1 s^? 1 depending on the preparation conditions of the PPS-modified electrodes.     

Desalination of whey by electrodialysis and ion exchange resins: analysis of both processes with regard to sustainability by calculating their cumulative energy demand

Desalination of whey is an important process in food technology and can be done either by electrodialysis (ED) or by ion exchange (IE) resins. The aim of the present paper is an assessment of the cumulative energy demand of both processes for a technical plant including production of the regeneration agents for the ion exchangers and treatment of waste water. A flow of 45 m³ per day of nanofiltered whey, which is three times concentrated and partially desalted, is assumed as feed for the plant. Data for the assessment was obtained from own laboratory experiments to be reported here, as well as from commercial plants. Applying IE, the final whey product is desalted to a degree of 99%. The IE process yields 3.7 m³ of waste water with 36.3 kg ash and an organic charge of 26 kg chemical oxygen demand (COD)/m³ feed whey. The energy demand of IE amounts to 0.15 kWh for pumping, 25.33 kWh for the production of the regenerants, and 9.75 kWh for the reduction of the organic charge/m³ whey. With ED, the final whey product is desalted to only 90%. ED yields 1.25 m³ of waste water with 8.1 kg ash and an organic charge of 8.4 kg COD/m³ whey. The energy demand of ED amounts to 4.2 kWh for pumping, 5.38 kWh for the electric current through the ED cells, and 3.16 kWh for the reduction of the organic charge/m³ whey.     

Enhanced Raman spectroscopy coupled to chemometrics for identification and quantification of acetylcholinesterase inhibitors

In this work, we present a new complete method using Surface Enhanced Raman Spectroscopy (SERS) and chemometrics for the qualitative and quantitative detection of pesticides by measuring the acetylcholinesterase (ACHE) activity. The Raman SERS is not only used for measuring the ACHE activity, but also for the direct detection of pesticides individually and for their identification. Gold nanoparticles (AuNPs) were used as dynamic SERS substrates for sensitive monitoring of ACHE activity in the presence of very low levels of organophosphate and carbamate pesticides, chemical warfare agents that are known to be ACHE inhibitors. The lowest detectable level for paraoxon was determined at 4.0 × 10⁻¹⁴ M and 1.9 × 10⁻⁹ M for carbaryl. The use of the enzyme allowed limits of detection for both pesticides that were much lower than the limits obtained by direct SERS analysis of the pesticides. The system shows a linear relationship between the intensity band at 639 cm⁻¹ and pesticide concentration. These results suggest that this biosensor could be used in the future for the non-selective detection of all ACHE inhibitors at very low concentrations with possible identification of the inhibitor.     

Photoelectrocatalytic activity of immobilized Yb doped WO_3 photocatalyst for degradation of methyl orange dye

Pure WO_3 and Yb:WO_3 thin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3 at% Yb:WO_3 film shows superior photoelectrochemical(PEC) performance than that of pure WO_3 film and it shows maximum photocurrent density(Iph= 1090 μA/cm~2) having onset potentials around +0.3 V/SCE in 0.01 M HClO_4. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange(MO) dye. Yb doping in WO_3 photocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand(COD) values.     

Asymmetric fluorination of β-keto esters catalyzed by chiral rare earth perfluorinated organophosphates

Novel chiral rare earth metal complexes bearing perfluorinated binaphthyl phosphate ligand RE[(R)-F₈BNP]₃ (RE = rare earth; F₈BNP = 5,5′,6,6′,7,7′,8,8′-octafluoro-1,1′-binaphthyl-2,2′-diyl phosphate) have been synthesized and used as a catalyst for the asymmetric electrophilic fluorination reaction of β-keto esters. The use of Sc[(R)-F₈BNP]₃ catalyst in combination with 1-fluoropyridinium triflate (NFPY–OTf) as a fluorinating agent was found to give the desired α-fluoro-β-keto esters in high chemical yields and enantiomeric excesses (up to 88% ee) under mild conditions.     

Electrochemical oxidation of vanillic acid by electro-Fenton process: Toward a novel route of protocatechuic acid electrosynthesis

The electrochemical oxidation of vanillic acid (VA) in acetone–water mixtures, was studied by electro-Fenton (EF) process in an undivided electro-chemical cell equipped with a carbon fiber cloth as cathode and Pt anode. The objective was the conversion of VA into protocatechuic acid (PCA) well known by its high added value. To our knowledge, the EF method was not used in organic electrosynthesis. The influence of several operating parameters, such as applied current, initial VA concentration and volumic percentage of acetone was investigated. The evolution of the concentrations of VA and its main oxidation product PCA during electrolyses was monitored by means of high performance liquid chromatography (HPLC). The experimental data indicated that the kinetics of VA disappearance follow a pseudo first and zero orders for initial VA concentrations respectively equals to 6.5 and (10, 20, 30) mmol L⁻¹. The maximum PCA concentration increases with volumic percentage of acetone and initial VA concentration. Under optimal experimental conditions of applied current (20 mA) and volumetric percentage of acetone (20%), the increase in the initial VA concentration leads to a linear increase in the maximum of PCA concentration. The very good selectivity rate of the oxidation of VA to PCA by the EF process, was interpreted by the stabilizing effects of acetone and especially the complexation of PCA by the iron ions.     

Na4Co2.4Mn0.3Ni0.3(PO4)2P2O7: High potential and high capacity electrode material for sodium-ion batteries

Na₄Co_2.4Mn_0.3Ni_0.3(PO₄)₂P₂O₇ has been evaluated as a positive electrode for sodium-ion batteries. The novel material has two redox couples around 4.2 V and 4.6 V and can deliver the high capacity of ca. 103 mAh g^− 1 at the high current density of 850 mA g^− 1 (5 C). X-ray absorption spectroscopy (XAS) results show that the redox reactions of Co, Mn and Ni ions proceed simultaneously in the charge process and it is indicated the novel material provide high mixed potential by the redox reactions of Co, Mn and Ni ions. These findings suggest that the derivatives of Na₄Co₃(PO₄)₂P₂O₇ should be employed as high potential and high capacity electrode materials.     

Stability constants of mixed ligand complexes of lead(II) with 1-(aminomethyl) cyclohexane acetic acid and α-amino acids

Formation of binary and ternary complexes of lead(II) ions with 1-(aminomethyl) cyclohexane acetic acid and some biologically important α-amino acids, such as glycine, l-alanine, l-valine, l-leucine, l-isoleucine, l-phenylalanine and l-proline was investigated using the potentiometric technique at 32 °C. The properties of mixed ligands were investigated and discussed. The acidity constants of the ligands and their stability constants were determined in 50% (v/v) DMSO-water medium under experimental conditions. The ternary complex formation was found to occur in a stepwise manner. The stability of ternary complexes was investigated and compared with that of the corresponding binary complex in terms of the parameters, Δ log K and log X. The concentration distribution of various species formed in the mixed ligand systems was evaluated.     

Thermodynamic studies on complexation of divalent transition metal ions with some zwitterionic buffers for biochemical and physiological research

The interaction between the zwitterionic buffers (3-[N-bis(2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid, N-(2-actamido)-2-aminoethane sulfonic acid, and 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid) with some divalent transition metal ions (Cu^II, Ni^II, Co^II, Zn^II, and Mn^II) were studied at different temperatures (298.15 to 328.15) K at ionic strength I = 0.1 mol · dm⁻³ NaNO₃ and in the presence of 10%, 30%, and 50% (w/w) dioxene by using potentiometry. The thermodynamic stability constants were calculated as well as the free energy change for the 1:1 binary complexation. The protonation constants of the zwitterionic buffers were also determined potentiometrically under the above conditions.