Showing papers on "Cyanide published in 2021"

Quantification of Active Site Density and Turnover Frequency: From Single-Atom Metal to Nanoparticle Electrocatalysts.

Abstract: Single-atom catalysts (SACs) featuring atomically dispersed metal cations covalently embedded in a carbon matrix show significant potential to achieve high catalytic performance in various electrocatalytic reactions. Although considerable advances have been achieved in their syntheses and electrochemical applications, further development and fundamental understanding are limited by a lack of strategies that can allow the quantitative analyses of their intrinsic catalytic characteristics, that is, active site density (SD) and turnover frequency (TOF). Here we show an in situ SD quantification method using a cyanide anion as a probe molecule. The decrease in cyanide concentration triggered by irreversible adsorption on metal-based active sites of a model Fe-N-C catalyst is precisely measured by spectrophotometry, and it is correlated to the relative decrease in electrocatalytic activity in the model reaction of oxygen reduction reaction. The linear correlation verifies the surface-sensitive and metal-specific adsorption of cyanide on Fe-N x sites, based on which the values of SD and TOF can be determined. Notably, this analytical strategy shows versatile applicability to a series of transition/noble metal SACs and Pt nanoparticles in a broad pH range (1-13). The SD and TOF quantification can afford an improved understanding of the structure-activity relationship for a broad range of electrocatalysts, in particular, the SACs, for which no general electrochemical method to determine the intrinsic catalytic characteristics is available.

Rational Design of an ICT-Based Chemodosimeter with Aggregation-Induced Emission for Colorimetric and Ratiometric Fluorescent Detection of Cyanide in a Wide pH Range.

Abstract: An alkoxy-substituted 1,3-indanedione-based chemodosimeter 1 with an aggregation-induced emission (AIE) characteristic was rationally designed and synthesized for the ultrasensitive and selective sensing of cyanide in a wide pH range of 3.0-12.0. The nucleophilic addition of cyanide to the β-conjugated carbon of the 1,3-indanedione group obstructs intramolecular charge transfer (ICT) and causes a significant change in the absorption and fluorescence spectra, enabling colorimetric and ratiometric fluorescent detection of cyanide in a 90% aqueous solution. The cyanide-sensing mechanism is supported by single-crystal X-ray diffraction analysis, time-dependent density functional theory (TD-DFT) calculations, and 1H NMR titration experiments. Sensor 1 exhibits strong yellow fluorescence in the solid state due to the AIE effect, and the paper probes containing 1 can be conveniently used to sense cyanide by the naked eye. Furthermore, chemodosimeter 1 was successfully used for sensing cyanide in real environmental water samples.

Biological treatment for the degradation of cyanide: A review

Abstract: Given that mining is considered to be an essential activity for Mexico's industrial development, cyanide has been increasingly used to recover precious metals such as gold and silver. Along with that arises the need to develop new technologies to treat the wastes (mining tailings). In addition to their high cyanide content, metal and other contaminants that are found in tailings also present a problem. As a result, conventional (physicochemical) strategies have been developed to reduce contamination from tailings, nonetheless, these have high operating costs and generate unwanted by-products. For this reason, studies have begun to focus on non-conventional strategies to treat free cyanide and cyanide complexes such as fungi, bacterial consortia, and pure bacteria. These are important because of the mechanisms involved in degrading or modifying contaminants at neutral to high pH levels, which convert contaminants into non-hazardous products. The ability of microorganisms to grow at an alkaline pH prevents HCN volatilization. These studies have been performed at the laboratory level using two types of microbial binding: suspended biomass and immobilized biomass. They have used both natural (granite rock, citrus peels, cellulose, gravel) and synthetic (stainless steel, geotextiles, alginate, plastics) packing material, as well as reactors with different types of flow, namely, batch and continuous.

Dimensionally stable anode (Ti/RuO2) mediated electro-oxidation and multi-response optimization study for remediation of coke-oven wastewater

Abstract: Electrochemical oxidation by means of dimensionally stable anodes (Ti/RuO2) was executed for the simultaneous elimination of various pollutants (such as COD, phenol, cyanide, and ammonia, etc.) from simulated and real coking-wastewater. A multiparameter variation study was also performed to investigate the operating range of certain operational parameters (such as pH, electrolyte, current density (CD), and H2O2 as a catalyst) and their effects on removal efficiencies of COD and rest of the pollutants of wastewater. To investigate the visual, morphological & elemental features of electrodes FE-SEM and EDX studies were performed before and after the treatment of wastewater. The electrochemical behavior was explored through cyclic voltammetry analysis. Moreover, the degradation and mineralization performance of organic material in wastewater was also investigated through LC-MS and total organic carbon (TOC) studies, respectively. A mathematical equation (model) was also developed to represent the multi-parameter optimization study using central composite design (CCD) through response surface methodology software (RSM tool). At the end of the process, the COD (90.13%), phenol (99.34%), cyanide (96.23%), and ammonia (94.43%) were eliminated within 180 min of reaction at optimum initial pH, NaCl (electrolyte), current density (CD), and H2O2 concentration of 8.0, 1.6 g/L, 24 mA/cm2 and 0.030 M, respectively.

Coumarin functionalized molecular scaffolds for the effectual detection of hazardous fluoride and cyanide

Abstract: Fluoride and cyanide contamination in drinking water imposes detrimental impacts on human health above their permissible limits. Hence, the quantitative detection of these colourless water-soluble toxins has attracted attention. Even though a plethora of chemosensors have been reported so far for the detection of fluoride and cyanide from various matrices, still their applicability is limited to a few examples. Nevertheless, recent advances in the syntheses of coumarin derivatives have shown significant impact on fluoride and cyanide detection. Therefore, this present review provides a brief overview of the application of coumarin-coupled molecular scaffolds towards the detection of perilous fluoride and cyanide along with their sensing mechanisms in order to develop more innovative, simple, sensitive, real-time responsive and cost-effective coumarin-based supramolecular chemosensors to promote next generation approaches towards the ultra-trace quantitative detection of these toxic anions.

A Cyaphide Transfer Reagent.

Abstract: The cyanide ion plays a key role in a number of industrially relevant chemical processes, such as the extraction of gold and silver from low grade ores. Metal cyanide compounds were arguably some of the earliest coordination complexes studied and can be traced back to the serendipitous discovery of Prussian blue by Diesbach in 1706. By contrast, heavier cyanide analogues, such as the cyaphide ion, C≡P-, are virtually unexplored despite the enormous potential of such ions as ligands in coordination compounds and extended solids. This is ultimately due to the lack of a suitable synthesis of cyaphide salts. Herein we report the synthesis and isolation of several magnesium-cyaphido complexes by reduction of iPr3SiOCP with a magnesium(I) reagent. By analogy with Grignard reagents, these compounds can be used for the incorporation of the cyaphide ion into the coordination sphere of metals using a simple salt-metathesis protocol.

Cyanide adsorption on activated carbon impregnated with ZnO, Fe2O3, TiO2 nanometal oxides: a comparative study

Abstract: Nanocrystalline metal oxides including TiO2, Fe2O3, and ZnO and their combinations were impregnated on activated carbon (AC) and characterized by XRD, FTIR, and FESEM analyses. The results showed the size of most Fe2O3/AC, TiO2/AC, TiO2/Fe2O3/AC, ZnO/AC, and ZnO/Fe2O3/AC particles are in the range of 25–60 nm. BET analysis verified the high surface area of the six adsorbents (201–448 m2/g). The adsorption results confirmed that the modification could improve the adsorption capacity and removal efficiency as the maximum monolayer adsorption capacity and cyanide removal efficiency were observed for ZnO/Fe2O3/AC (101.0 mg/g, 82.5%), TiO2/Fe2O3/AC (96.2 mg/g, 75.1%), ZnO/AC (91.7 mg/g, 73.5%), TiO2/AC (90.9 mg/g, 72.4%), Fe2O3/AC (86.2 mg/g, 69.2%,), and AC (78.1 mg/g, 66.3%), respectively. Moreover, the study of different isotherm models including Langmuir, Freundlich, and Redlich–Peterson indicated that the Langmuir model was the most suitable one for the six adsorbents with 0.56 < RL < 0.64. The kinetic modeling of experimental data revealed the cyanide adsorption on all adsorbents followed the pseudo second-order model confirming chemisorption can be a main mechanism of adsorption. The regeneration and reusability results showed modified AC adsorbents have more reusable and stable structure than AC to be used as adsorbents in industrial wastewaters. The performance of adsorption process was compared with different methods of cyanide removal. The results approved that adsorption process as a cost-effective and simple design method using bioadsorbents can be highly effective in full-scale applications for the removal of high concentration of cyanide.

Meso-porous activated carbon from lignite waste and its application in methylene Blue adsorption and coke plant effluent treatment

Abstract: Coke plant wastewater contains many toxic pollutants such as phenol, cyanide, and ammonia, etc., handling and disposal of which has a significant impact on the environment and human health. A novel adsorbent based on lignite extraction waste was prepared and its effect on the removal of simulated methylene blue, phenol and colour (ortho, para-benzo quinone) from real coking wastewater was investigated. Lignite waste (residue) after humic acid separation has a significant quantity of oxidized functional groups along with residual KOH, which makes it suitable for the preparation of activated carbon with high surface area. Since hydrothermal extraction breaks coal-mineral-pore aggregate, the separation efficiency of ash-bearing minerals improved, 11 % ash coal prepared from the residue with 81.6 % yield. Prepared activated carbon from low ash residue has a mesoporous surface (49.8 nm pore size), 0.554 cm3/g of total pore volume, and 980 m2/gram BET surface area. The adsorption kinetics followed pseudo-second order (R2 = 0.984) for methylene blue, pseudo-second-order (R2 = 0.978) for phenol, and pseudo-first-order (R2 = 0.935) for colour adsorption. Adsorption isotherm at equilibrium shows a maximum adsorption capacity of 120 mg/g for methylene blue, 20.49 mg/g for phenol and 588.23 PtCo/g for colour. The adsorption isotherm was in good agreement with Langmuir isotherm (R2 = 0.989−0.994) compared to Freundlich model (R2 = 0.924−0.982). The presence of negatively charged surface favours the uptake of cationic groups. Apart from phenol and colour, the adsorbent can remove total organic carbon (TOC) by 93.6 % and thiocyanide by 6.7 %. Adsorbent reutilization studies show that, the regenerated adsorbent by thermal treatment can be used for 3 cycles.

Predicting the capability of diatomite magnano composite boosted with polymer extracted from brown seaweeds for the adsorption of cyanide from water solutions using the response surface methodology: modelling and optimisation

Abstract: The rate of cyanide reduction in the aqueous solutions by adsorption onto the diatomite magnano composite boosted with alginate polymer beads (DMBA) was evaluated. The R software using RSM was used...

A Green and Sustainable Process for the Recovery of Gold from Low-Grade Sources Using Biogenic Cyanide Generated by Bacillus megaterium: A Comprehensive Study

Abstract: The decreasing grade of gold deposits and environmental regulations concerning the use of cyanide, a conventional extraction agent used in gold recovery, has highlighted the challenge in the field ...

Phycoremediation of pollutants from coke-oven wastewater using Tetraspora sp. NITD 18 and estimation of macromolecules from spent biomass

Abstract: Coke-oven wastewater contains an array of hazardous pollutants like cyanide, phenol, ammoniacal-N, etc. The main objective of the present study is to assess the effectiveness of phycoremediation technique as tertiary treatment for simultaneous removal of three model pollutants such as phenol, ammoniacal-N, and cyanide from secondary treated coke-oven wastewater. A green route was employed for the treatment of coke-oven wastewater via the use of Tetraspora sp. NITD 18, collected from a contaminated site. Strain susceptibility was tested for the growth in the simulated solution of phenol (10−300 mg/L), ammoniacal-N (100−800 mg/L), and cyanide (1−10 mg/L), and subsequently, optimum concentration was assessed as 100 mg/L, 400 mg/L, and 2 mg/L, respectively. pH 7 and inoculum concentration 10 % was found suitable for the removal of phenol (79.02 ± 6.93 %), ammoniacal-N (74.7 ± 5.07 %), and cyanide (80.4 ± 0.015 %) from their individual solution at optimal initial concentrations after 14 days. For solutions of individual pollutants, preferred pollutants were examined on the basis of production of biomass with respect to time, and found the following order: ammoniacal-N > phenol > cyanide. The solution of mixed pollutants was prepared by mixing the said pollutants at their optimal level of initial concentrations at a suitable pH (7). Such a solution was termed as simulated coke-oven wastewater (SCOW). While the present investigation deals with co-current removal of pollutants from simulated coke-oven wastewater (SCOW) and real secondary treated coke-oven wastewater at laboratory scale, the continuous study on real wastewater at industrial scale with the isolated algal strain is the scope of the future work.

Old Materials for New Functions: Recent Progress on Metal Cyanide Based Porous Materials.

Abstract: Cyanide is the simplest ligand with strong basicity to construct open frameworks including some of the oldest compounds reported in the history of coordination chemistry. Cyanide can form numerous cyanometallates with different transition metal ions showing diverse geometries. Rational design of robust extended networks is enabled by the strong bonding nature and high directionality of cyanide ligand. By virtue of a combination of cyanometallates and/or organic linkers, multifunctional framework materials can be targeted and readily synthesized for various applications, ranging from molecular adsorptions/separations to energy conversion and storage, and spin-crossover materials. External guest- and stimuli-responsive behaviors in cyanide-based materials are also highlighted for the development of the next-generation smart materials. In this review, an overview of the recent progress of cyanide-based multifunctional materials is presented to demonstrate the great potential of cyanide ligands in the development of modern coordination chemistry and material science.

Photoconversion of Cyanide to Dinitrogen Using the Durable Electrode of a TaON Overlayer-Deposited WO3 Film and Visible Light

Abstract: Chemical treatments of toxic cyanide (CN–) typically involve its conversion to cyanate (OCN–), which is less toxic. An ideal treatment should be its conversion to N2 and CO2. This study proposed an...

Boron fluoride regulated “naked eye” and ratiometric fluorescent detection of CN− as a test strip and its bioimaging

Abstract: Cyanide ions (CN−) are widely used in chemical and industrial processes, but not only can they cause environmental pollution, what is worse is that when a small amount of cyanide enters the human body, in the less severe cases, they pose health risks, and in the more severe cases, they can lead to death. The development of a practical cyanide probe is extremely urgent. In this work, with α,β-unsaturated ketones conjugated with ethylenediamine coumarin as a fluorophore and reaction site, boron fluoride was introduced to adjust the ICT and reactivity to construct a ratiometric fluorescent probe for the highly sensitive detection of CN−. The process was rapid within 40 s and can be monitored by the naked eye. The probe demonstrated a low detection limit (0.072 μM). Furthermore, the probe was used to detect CN− in the test strip, soil, and water. In addition, cell imaging experiments indicated the probe can be used in biological determination of cyanide poisoning.

Physiological concentrations of cyanide stimulate mitochondrial Complex IV and enhance cellular bioenergetics.

Abstract: In mammalian cells, cyanide is viewed as a cytotoxic agent, which exerts its effects through inhibition of mitochondrial Complex IV (Cytochrome C oxidase [CCOx]). However, the current report demonstrates that cyanide's effect on CCOx is biphasic; low (nanomolar to low-micromolar) concentrations stimulate CCOx activity, while higher (high-micromolar) concentrations produce the "classic" inhibitory effect. Low concentrations of cyanide stimulated mitochondrial electron transport and elevated intracellular adenosine triphosphate (ATP), resulting in the stimulation of cell proliferation. The stimulatory effect of cyanide on CCOx was associated with the removal of the constitutive, inhibitory glutathionylation on its catalytic 30- and 57-kDa subunits. Transfer of diluted Pseudomonas aeruginosa (a cyanide-producing bacterium) supernatants to mammalian cells stimulated cellular bioenergetics, while concentrated supernatants were inhibitory. These effects were absent with supernatants from mutant Pseudomonas lacking its cyanide-producing enzyme. These results raise the possibility that cyanide at low, endogenous levels serves regulatory purposes in mammals. Indeed, the expression of six putative mammalian cyanide-producing and/or -metabolizing enzymes was confirmed in HepG2 cells; one of them (myeloperoxidase) showed a biphasic regulation after cyanide exposure. Cyanide shares features with "classical" mammalian gasotransmitters NO, CO, and H2S and may be considered the fourth mammalian gasotransmitter.

Cassava flour extracts solution to induce gelatin cross-linked activated carbon-graphene oxide composites: The adsorption performance of dyes from aqueous media

Abstract: To enhance the performance of activated carbon (AC) for dyes removal, this study proposed a new composite of cassava flour solution extracts-cross-linked activated carbon and graphene oxide (named as AC-GO) to efficiently remove dyes from an aqueous solution. The designed routes involved creatively introducing cassava flour extracts solution (CES) to induce the conjugation and precipitation of the activated carbon and graphene oxide within a minute at a temperature of 60-100°C. The AC-GO composites were prepared from both powder and granulated activated carbon (PAC-GO and GAC-GO) and were characterized via several techniques such as Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), FTIR, N2 adsorption-desorption curves, etc... Phenomena prove that the carbohydrates, cyanide acid, protein, minerals, and sulfur group in CES play a role in the formation of intermolecular cross-linkage with small polar compounds in GO and AC during the thermal treatment process. Results of characterization demonstrated that thin GO films were coated on AC. Promotions of specific surface area after supporting GO compared to that of PAC and GAC were observed. The evaluation of their performance indicated that the methylene blue trihydrate (MB) was totally removed by AC-GO at a low concentration (10-50 mg/L). The relatively good performance for the removal of Direct Red 23 (DR23) by the composites was observed. The adsorption capacity of MB and DR23 by PAC-GO was 248.14 mg/g and 114.81 mg/g, respectively, while for MB and DR23 by GAC-GO, they were 222.72 mg/g and 66.80 mg/g, respectively.