Elimination Of Cyanide Research Articles

Synthesis of Stilbenes by Cyanide/Base-Mediated Coupling of Benzylic Chlorides and Alcohols

AbstractA straightforward procedure has been developed for the direct synthesis of stilbenes from benzylic chlorides and alcohols. The transformation employs a two-step one-pot protocol where the benzylic chloride is first subjected to a substitution with potassium cyanide in o-xylene. Without workup, the resulting arylacetonitrile is then reacted directly with the benzylic alcohol and potassium tert-butoxide to generate the stilbene framework. The condensation has been performed with a variety of commercially available benzylic chlorides and alcohols to afford substituted stilbenes as the pure E-isomers. A kinetic isotope effect of 5.2 has been measured for the overall transformation when comparing benzyl alcohol and α,α-d 2-benzyl alcohol. The release of cyanide during the final elimination to stilbene has been confirmed by a picrate test. Thus, the potassium tert-butoxide-mediated elimination of cyanide is believed to proceed by an E1cB mechanism where the deprotonation reaction constitutes the rate-determining step.

Cyanide removal from aqueous solution by oxidation with hydrogen peroxide in the presence of activated alumina-supported copper catalyst

<p>Cyanide compounds are widely used in some electroplating, chemical and metallurgical industries. They are often found in their liquid discharges. This work highlights the performance of an activated alumina-supported copper catalyst in the removal of cyanide by oxidation with hydrogen peroxide in aqueous solution. The influence of catalyst dose, initial molar ratio of hydrogen peroxide/cyanides, temperature, and catalyst reuse was studied. The activated alumina-supported copper significantly enhanced the reaction rate showing a good catalytic activity. The efficiency of cyanide elimination was increased after 30 minutes of oxidation from 48% to 98% by increasing the catalyst dose from 1 to 10 g/L. Rising the temperature from 30°C to 40°C promoted cyanide removal. The catalyst can be recycled four times and show good stability. The kinetics of cyanide oxidation was revealed to be pseudo-first order with regarding cyanides. The rate constants as well as the activation energy were determined.</p>

Effect of ozonation and UV-LED combination on simultaneous removal of toxic elements during electrocoagulation.

Cyanide and heavy metals pose significant risks as contaminants in certain industrial effluents. This study aims to concurrently eliminate cyanide and specific heavy metals from synthetic wastewater resembling gold processing effluent, employing an improved electrocoagulation method incorporating ozone and UV-LED. The investigation delves into the effects of pH, electrode type, current density, reaction time, and ozonation. The findings revealed notable removal efficiencies: 98% for cyanide, 76% for nickel, 85% for copper, and 84% for zinc when utilizing a stainless steel electrode as the cathode. Optimal removal rates were achieved at 94% for cyanide, 93% for copper, 92% for zinc, and 83% for nickel, employing the UV-LED-ozone technique with an ozonation flow rate of 4mg/s at pH = 10. Notably, when Al-Gr-SS-Fe electrodes and a current of 15mA/cm2 were applied, these removal efficiencies were observed. Therefore, the most favorable conditions for the concurrent removal of pollutants from synthetic wastewater involved maintaining a pH of 10, utilizing SS-Fe as anode and Al-Gr as cathode electrodes, and employing a current density of 15mA/cm2. The addition of ozonation with a flow rate of 4mg/s, along with UV-LED, further enhanced the removal process. In summary, it can be inferred that the enhanced electrocoagulation method outperformed conventional electrocoagulation, leading to increased elimination of cyanide and selected heavy metals.

Regioselective synthesis of some new pyrazole and isoxazole derivatives incorporating benzothiazole moiety: Experimental and theoretical studies

Nitrile imine derivative 3 added regioselectively to α-(benzothiazol-2-yl)cinnamonitrile derivatives 1a–c to afford 5-(benzothiazol-2-yl)-5-cyano-4,5-dihydro-1H-pyrazole derivatives 4a–c. Compound 4a underwent thermal elimination of hydrogen cyanide in sodium ethoxide solution to give the pyrazole derivative 6. The isoxazole derivative 10 was synthesized by reacting nitrile oxide 8 with cinnamonitrile derivative 1d. The structures of the synthesized compounds were characterized by FT-IR, NMR, and MS spectroscopic techniques. The reaction mechanism was studied via density functional theory (DFT) quantum chemical calculations at the B3LYP/6-31G (d) level of theory.

Synthesis of ASB-CuO nanocomposite for efficient cyanide degradation from aqueous systems: Fundamentals and potential applications to tailings water from gold operations

Synthesis of nanoparticles through physical and chemical processes for several applications is common, but it is often expensive and involves inorganic chemicals. For the first time, in this study, a simple and novel approach for producing a CuO-loaded Alocasia macrorrhizos stem biomass (ASB–CuO) nanocomposite that is effective in cyanide degradation has been presented. The CuO nanoparticles (CuO NPs) synthesis was revealed by UV spectroscopy at a wavelength of 247 nm. The CuO NPs on the dried ASB surface were well scattered and mostly spherical, as revealed by SEM/EDX analysis. The crystalline structure of ASB–CuO was established by XRD investigations. For the elimination of cyanide from aqueous systems, it was shown that the nanocomposite of ASB–CuO had a higher removal performance than the raw ASB. A catalytic test on the efficacy of ASB–CuO in removing cyanide (100 mg/L) from wastewater revealed a removal efficiency of 90% within 60 min. Different factors, such as contact time, dosage, initial concentration, and temperature were examined. The cyanide removal followed pseudo-second-order kinetics with the ASB–CuO having higher rate constant than the raw ASB. Furthermore, the produced nanocomposite was able to remove 90% of cyanide from real wastewater samples, as demonstrated by removal studies on the tailings water samples of a gold cyanidation operation.

Characterization of the Oxazinomycin Biosynthetic Pathway Revealing the Key Role of a Nonheme Iron-Dependent Mono-oxygenase.

Oxazinomycin is a C-nucleoside natural product with antibacterial and antitumor activities. In addition to the characteristic C-glycosidic linkage shared with other C-nucleosides, oxazinomycin also features a structurally unusual 1,3-oxazine moiety, the biosynthesis of which had previously been unknown. Herein, complete in vitro reconstitution of the oxazinomycin biosynthetic pathway is described. Construction of the C-glycosidic bond between ribose 5-phosphate and an oxygen-labile pyridine heterocycle is catalyzed by the C-glycosidase OzmB and involves formation of an enzyme-substrate Schiff base intermediate. The DUF4243 family protein OzmD is shown to catalyze oxygen insertion and rearrangement of the pyridine C-nucleoside intermediate to generate the 1,3-oxazine moiety along with the elimination of cyanide. Spectroscopic analysis and mutagenesis studies indicate that OzmD is a novel nonheme iron-dependent enzyme in which the catalytic iron center is likely coordinated by four histidine residues. These results provide the first example of 1,3-oxazine biosynthesis catalyzed by an unprecedented iron-dependent mono-oxygenase.

Effectiveness and mechanism of cyanide remediation from contaminated soils using thermally activated persulfate

Persulfate (PS)-based advanced oxidation processes have been frequently employed for contaminant remediation, but the effectiveness of PS oxidation for the elimination of cyanide-bearing contaminants from soil, and the underlying mechanisms, have rarely been explored. This study investigated the degradation of two iron-cyanide (Fe–CN) complexes (ferricyanide and ferrocyanide) with thermally activated PS via two remediation strategies, namely one-step oxidation (direct PS oxidation) and two-step oxidation (alkaline extraction followed by PS oxidation). The two-step oxidation process was more effective for the elimination of cyanide pollutants from soil, reaching >94% remediation efficiency for both Fe–CN complexes studied. The presence of dissolved soil components, especially soil organic matter, increased consumption of PS during the remediation process. A combined analysis based on electron paramagnetic resonance (EPR), free radical scavenging, and degradation product identification revealed that SO4- and HO were the principal reactive radicals responsible for Fe–CN degradation. Based on the determination of radical species and identification of decomposition products, a transformation pathway for Fe–CN complexes during thermally activated PS oxidation is proposed. Overall, this study demonstrates the effectiveness of the thermally activated PS oxidation technique for cyanide elimination from polluted soil. Further study is required to verify the feasibility of this method for field applications.

Effect of ultrasonic pretreatment on eliminating cyanogenic glycosides and hydrogen cyanide in cassava

Traditional soaking method takes days to remove cassava cyanide. Ten minutes of ultrasonic pretreatment (UPT) was found to be a new effective method to eliminate both cyanogenic glycosides and hydrogen cyanide in cassava. Here, the parameters of UPT were optimized and the underlying mechanisms were investigated. 40.36% and 24.95% of hydrogen cyanide and cyanogenic glycosides in cassava juice were eliminated under 10 min of UPT (45℃, 81 W). UPT before boiling enhanced the total cyanide elimination to 41.94%. The degradation patterns of hydrogen cyanide and cyanogenic glycosides were different. Ultrasound directly eliminated hydrogen cyanide and indirectly degraded cyanogenic glycosides through promoting enzymatic hydrolysis. The β-glucosidase activity was increased by 17.99% induced by ultrasound. This was supported by the movement of hydrophobic residual and the rearrangement of the secondary structure of the molecular as found in fluorescence, CD, FTIR, DSC and TG analysis. This study revealed that UPT acted as a fast and simple technical way in improving cassava safety.

Phytoremediation potential of water hyacinth (Eichhornia crassipes) for phenol and cyanide elimination from synthetic/simulated wastewater

Water pollution is increasing due to urbanization and industrialization. Waste water pollution raised concern because of its influence on plants and humans. Water hyacinth (Eichhornia crassipes) is used for the removal of pollutants because of its phytoremediation efficiency. In this study, water hyacinth (Eichhornia crassipes) has been tested for simultaneous elimination of phenol and cyanide from mono and binary component aqueous solution in batch systems. The plant was grown at six concentrations of phenol and cyanide in the ratio of (10:1), i.e. 100:10, 200:20, 300:30, 500:50, 700:70 and 1000:100 mg/L in aqueous solution. The effect of process parameters such as initial concentration of phenol and cyanide and pH was evaluated. The plant was found capable of eliminating up to 96.42% of phenol (300 mg/L) and 92.66% of cyanide (30 mg/L) during the 13 days cultivation time at pH 8. The calculated Km of the root length elongation for phenol was 5.20 mm and the Vmax was 12.52 μg phenol/g root/h. However, the calculated Km of the root length elongation for cyanide was 0.39 mm and the Vmax was 14.99 μg cyanide/ g root/h. In the Eichhornia crassipes plant, the biochemical parameters such as chlorophyll, protein and sugar content have been indicated a decreasing trend due to uptake of phenol and cyanide throughout cultivation. Toxicity to 100–1000 mg/L of phenol and 10–100 mg/L of cyanide was measured by measuring the relative transpiration over 13 days. At 100 mg/L of phenol and 10 mg/L of cyanide, only a small reduction in transpiration but no morphological changes were noticed. Both pollutants are absorbed through the root of the Eichhornia crassipes plant by plasmalemma and become accumulated into the root cells and stem of a plant. Thus, this study will be beneficial for the decontamination of highly polluted waste water.

Degradation of cyanide from gold processing effluent by H2O2, NaClO and Ca(ClO)2 combined with sequential catalytic process

This work investigates the removal of cyanide as a noxious pollutant in the gold processing effluent (Aq-Dara mine, Takab, Iran) using H2O2, H2O2+Fe(II) (Fenton), H2O2+Cu(II), NaClO and Ca(ClO)2 oxidants. Implementation of purification operation was carried out by varying the parameters including pH, oxidant dosage, temperature and time of the reaction. The results show that the oxidants have the highest efficacy at pH 10-12, while the Fenton process has the highest efficiency at pH 8. The results confirm that Ca(ClO)2 is the best oxidant due to the shorter time, low reaction rate, high degradation of cyanide and low cost. The obtained results of response surface methodology optimization show that cyanide degradation has a direct relation to temperature, amount of oxidant, time and catalyst dosage parameters and has an inverse relation to pH. Also, the cyanide elimination efficiency is more than 99.5% and residual cyanide less than Environmental Protection Agency standards and 40% of the consumed water can be compensated by the effluent treatment and its return to the factory's processing circuit. Keywords: Oxidation Process; Gold Processing Effluents Treatment; Cyanide Degradation; Non-linear Kinetic Modeling, Response Surface Method.

Extension of pilot tests of cyanide elimination by ozone from blast furnace gas washing water through Aspen Plus® based model

For improving wastewater quality, one of the dare of steelworks is reducing cyanide in wastewater of gas washing treatment of blast furnaces. Costs of existing treatments, stringent environmental regulations and changeable composition of water from gas treatment, have led to study how available treatments can be modified and to examine new ones. Ozonation is one of cyanide treatments, tested within a European project. A process model was set up with Aspen Plus®, to assess operating conditions and wastewater distinctive characteristics and to demonstrate treatment robustness. Process was modeled by theoretical reactors, taking into account all more affecting reactions. A genetic algorithm was exploited to find kinetic parameters of these reactions. After validation, the model was used to analyse scenarios, by considering also real contexts. Pilot tests were extended, process knowledge was enhanced and suggestions were obtained. To promote cyanide removal with ozone, temperature and pH values were 30°C and 10, respectively. With an ozone (mg/h)/ water (L/h) ratio of 100 mg/L, batch mode ensure reaching cyanide regulation limit (0.2 mg/L) after maximum 4.5 h, if initial amount was less than 20 mg/L. Higher removal was obtained than in continuous mode due to constraints related to this last run. Higher wastewater contamination needed further time and more ozone.

Oxygenophilic Lewis Acid Promoted Synthesis of 2-Arylindoles from Anilines and Cyanoepoxides in Alcohol.

A convenient synthetic method to indoles from anilines and cyanoepoxides was developed under the catalysis of BF3·OEt2 or AlCl3 in alcohols. The reaction involves a tandem reaction of the regiospecific ring-opening of cyanoepoxides with anilines, elimination of cyanide, intramolecular aromatic electrophilic substitution, and water elimination. The Lewis acid generated protic acid is an efficient catalyst. The method features readily accessible starting materials, wide substrate scope, transition-metal-free environment, and regiospecificity in the ring-opening of cyanoepoxides.

Acceptorless and Base‐free Dehydrogenation of Cyanohydrin with (η6‐Arene)halide(Bidentate Phosphine)ruthenium(II) Complex

AbstractRuthenium‐catalyzed dehydrogenation of cyanohydrins under acceptorless and base‐free conditions was demonstrated for the first time in the synthesis of acyl cyanide. As opposed to the thermodynamically preferred elimination of hydrogen cyanide, the dehydrogenation of cyanohydrins could be kinetically controlled with ruthenium (II) bidentate phosphine complexes. The effects of the arene, phosphine ligands and counter anions were investigated in regard to catalytic activity and selectivity. Selective dehydrogenation can occur via β‐hydride elimination with the experimentally observed [(alkoxide)Ru] complex.magnified image

Photoswitching of Dihydroazulene Derivatives in Liquid-Crystalline Host Systems.

Photoswitches and dyes in the liquid-crystalline nematic phase have the potential for use in a wide range of applications. A large order parameter is desirable to maximize the change in properties induced by an external stimulus. A set of photochromic and nonphotochromic dyes were investigated for these applications. It was found that a bent-shaped 7-substituted dihydroazulene (DHA) photoswitch exhibited liquid-crystalline properties. Further investigation demonstrated that this material actually followed two distinct reaction pathways on heating, to a deactivated form by a 1,5-sigmatropic shift and to a linear 6-substituted DHA. In addition, elimination of hydrogen cyanide from the photoactive DHA gave both bent and linear azulene dyes. In a nematic host that has no absorbance around 350 nm, it was found that only the linear DHA derivative has nematic properties; however, both 6- and 7-substituted DHAs were found to have large order parameters. In the nematic host, ring opening of either DHA to the corresponding vinylheptafulvene resulted in a decrease in dichroic order parameter and an unusually fast back-reaction to a mixture of both DHAs. Likewise, only the linear azulene derivative showed mesomorphic properties. In the same nematic host, large order parameters were also observed for these dyes.

Potential of Ipomoea aquatica for elimination of phenol and cyanide from mono and binary component aqueous solution in a photosynthesis chamber

Potential of Ipomoea aquatica for elimination of phenol and cyanide from mono and binary component aqueous solution in a photosynthesis chamber

Equilibrium isotherm and kinetic studies for the simultaneous removal of phenol and cyanide by use of S. odorifera (MTCC 5700) immobilized on coconut shell activated carbon

In this study, simultaneous removal of phenol and cyanide by a microorganism S. odorifera (MTCC 5700) immobilized onto coconut shell activated carbon surface (CSAC) was studied in batch reactor from mono and binary component aqueous solution. Activated carbon was derived from coconut shell by chemical activation method. Ferric chloride (Fecl3), used as surface modification agents was applied to biomass. Optimum biosorption conditions were obtained as a function of biosorbent dosage, pH, temperature, contact time and initial phenol and cyanide concentration. To define the equilibrium isotherms, experimental data were analyzed by five mono component isotherm and six binary component isotherm models. The higher uptake capacity of phenol and cyanide onto CSAC biosorbent surface was 450.02 and 2.58 mg/g, respectively. Nonlinear regression analysis was used for determining the best fit model on the basis of error functions and also for calculating the parameters involved in kinetic and isotherm models. The kinetic study results revealed that Fractal-like mixed first second order model and Brouser–Weron–Sototlongo models for phenol and cyanide were capable to offer accurate explanation of biosorption kinetic. According to the experimental data results, CSAC with immobilization of bacterium S. odorifera (MTCC 5700) seems to be an alternative and effective biosorbent for the elimination of phenol and cyanide from binary component aqueous solution.

Batch growth kinetic studies for elimination of phenol and cyanide using mixed microbial culture

The efficiency of a mixed microbial culture to eliminate phenol and cyanide from aqueous solution was estimated in a batch process. The influence of initial concentration of phenol and cyanide on the microbial growth was calculated for the range of initial concentration between 50 and 1500mg/L of phenol and 5–150mg/L of cyanide. A maximum specific growth rate of 0.0663h−1 was observed at 250mg/L of phenol and 0.143h−1 at 25mg/L of cyanide concentration in the growth medium. The specific growth rate of the culture followed substrate inhibition kinetics. Monod, Haldane, Edward, Yano and Koga, Luong, Han-Levenspiel, and Powell growth kinetic models were used to determine the growth kinetics of mixed culture. Edward, Luong and Han and Levenspiel models were established as best fit to the specific growth rate data for phenol. However, for cyanide Haldane and Edward models were found to be best with lowest Marquardt’s percent standard deviation (MPSD) values. The degradation kinetics of phenol and cyanide was found to follow a three-half order model at all initial concentrations with lowest MPSD value.

Simultaneous removal of phenol and cyanide from aqueous solution by co-culture of strain immobilized onto coconut shell activated carbon

In this study, the simultaneous biosorption and bioaccumulation of phenol and cyanide by co-culture/mixed culture of Pseudomonas putida (MTCC 1144) and Serratia odorifera (MTCC 5700) strains immobilized onto coconut shell activated carbon (CSAC) were investigated. The batch experiments were performed for the elimination of phenol and cyanide from mono and binary aqueous solution using initial concentrations of phenol (100–1,000 mg/L) and cyanide (10–100 mg/L). Under optimum conditions, the CSAC was demonstrated a biosorption capacity 500.55 mg/g of phenol and 2.41 mg/g of cyanide at pH 8, biomass dose 30 g/L and temperature 30°C. In a binary component system among six multicomponent isotherms, extended Freundlich model indicates a better fit for both phenol and cyanide. Moreover, the kinetic experimental results show that both phenol and cyanide were defined by the pseudo-first-order kinetic model. Thermodynamic study was established that the simultaneous biosorption and bioaccumulation of phenol indicates the exothermic nature of the process and cyanide indicates the endothermic nature of the process.

Simultaneous removal of phenol and cyanide from aqueous solution by adsorption onto surface modified activated carbon prepared from coconut shell

The present study is devoted to the elimination of phenol and cyanide from binary component aqueous solution by adsorption onto copper impregnated coconut shell activated carbon (Cu-CSAC). Effects of initial concentration, adsorbent dose, pH, temperature and contact time on phenol and cyanide elimination have been examined. At an optimum temperature 30°C, pH 8, and the adsorbent dose of 40g/L, 71.43% phenol and 86.8% cyanide were removed from binary aqueous solution comprising 300mg/L of phenol and 30mg/L of cyanide. The isotherm modeling study is carried out by accompanying batch experiments at range of initial concentration 100–1000mg/L of phenol and 10–100mg/L of cyanide. Three mono component isotherm model and six binary component isotherm models were considered. The model parameters were predicted by using non-linear regression analysis technique. It was observed that the experimental data indicate a better fit with an Extended Freundlich isotherm model for adsorption of phenol and cyanide in the binary component system. The adsorption efficiency of Cu-CSAC was observed to be 239.85mg/g of phenol and 5.30mg/g of cyanide. The mechanism of adsorption process was found chemisorption followed by Pseudo second order kinetics. Thermodynamic studies indicated the adsorption process onto Cu-CSAC as endothermic nature and reversible.

Continuous packed bed adsorption of phenol and cyanide onto modified rice husk: an experimental and modeling study

The current study estimates the feasibility of modified rice husk (MRH) in eliminating phenol and cyanide from binary aqueous solution through packed bed column studies. The influence of varying initial concentration, flow rate, and bed depth on the performance of packed column was examined. The experimental data for the packed bed column were applied in different kinetic model such as the Thomas, Adams–Bohart, Yoon–Nelson, and Wolborska model to calculate the breakthrough curve and to define the representative parameters of the packed bed column beneficial for scheming large-scale column studies. The Thomas model is to be found best for phenol, whereas Yoon–Nelson Model provided good agreement with experimental data (R2 > 0.85) for both phenol and cyanide. This model was designed to calculate the 50% breakthrough time attained by the packed bed column system and provided the predictable breakthrough time for the packed bed columns that were not exhausted throughout the process. Average relative error was applied to estimate the characteristics of the predicted and experimental values under the corresponding models to observe the best fit model. The MRH packed bed column could be effectively used up to six cycles of adsorption/desorption for the elimination of phenol and cyanide, respectively.