Highly Efficient Separation of Ethanol Amines and Cyanides via Ionic Magnetic Mesoporous Nanomaterials.

Simple and efficient sample pretreatment methods are important for analysis and detection of chemical warfare agents (CWAs) in environmental and biological samples. Despite many commercial materials or reagents that have been already applied in sample preparation, such as SPE columns, few materials with specificity have been utilized for purification or enrichment. In this study, ionic magnetic mesoporous nanomaterials such as poly(4-VB)@M-MSNs (magnetic mesoporous silicon nanoparticles modified by 4-vinyl benzene sulfonic acid) and Co2+@M-MSNs (magnetic mesoporous silicon nanoparticles modified by cobalt ions) with high absorptivity for ethanol amines (EAs, nitrogen mustard degradation products) and cyanide were successfully synthesized. The special nanomaterials were obtained by modification of magnetic mesoporous particles prepared based on co-precipitation using -SO3H and Co2+. The materials were fully characterized in terms of their composition and structure. The results indicated that poly(4-VB)@M-MSNs or Co2+@M-MSNs had an unambiguous core-shell structure with a BET of 341.7 m2·g-1 and a saturation magnetization intensity of 60.66 emu·g-1 which indicated the good thermal stability. Poly(4-VB)@M-MSNs showed selective adsorption for EAs while the Co2+@M-MSNs were for cyanide, respectively. The adsorption capacity quickly reached the adsorption equilibrium within the 90 s. The saturated adsorption amounts were MDEA = 35.83 mg·g-1, EDEA = 35.00 mg·g-1, TEA = 17.90 mg·g-1 and CN-= 31.48 mg·g-1, respectively. Meanwhile, the adsorption capacities could be maintained at 50-70% after three adsorption-desorption cycles. The adsorption isotherms were confirmed as the Langmuir equation and the Freundlich equation, respectively, and the adsorption mechanism was determined by DFT calculation. The adsorbents were applied for enrichment of targets in actual samples, which showed great potential for the verification of chemical weapons and the destruction of toxic chemicals.

Effect of cyanide ions (CN-) extracted from cassava (Manihotesculenta Crantz) on Alveolar Epithelial Cells (A549 cells).

Cassava (Manihotesculenta Crantz) is one of the most important root crops in tropical countries. It is a major source of cyanogenic glycosides viz. linamarin and lotaustralin, and these on breakdown liberate HCN and ketone. Cassava cyanide extract (CCE) from cassava leaves and tuber rinds were formulated as a biopesticide against certain borer insect pests of horticultural crops. Adenocarcinomic human alveolar basal epithelial cells (A549) were treated with three different concentrations (100, 200, 400 ppm) of CCE. The MTT and NRU assays showed dose-dependent cytotoxicity. The DCFH-DA assay does not show any free radical scavenging activity, whereas the NRR assay showed a reduction in the nitrile radicals with an increase in the concentration of the bioactive compound. A negative correlation was found between the concentration of the bioactive principles and mitochondrial and lysosomal functions. Various cellular assays demonstrated the cellular response of the CCE, and it was found that at higher concentration (400 ppm), the CCE exert a significant necrotic cell death rather than apoptosis. The results of the study indicated that the CCE have a remarkable tendency of anti-proliferative ability.

Synthetic heme protein models that function in aqueous solution.

Myoglobin (Mb) is considered as the optimal system for capturing molecular oxygen (O2) in aqueous solution under natural conditions. Therefore, the preparation of artificial systems that mimic the function of Mb is a long-standing and challenging objective. Various sophisticated iron porphyrins have been designed and synthesized to realize O2 biding at their axial positions. Although all of these compounds reversibly bind O2 in absolute organic solvents, no stable O2 adducts were obtained in aqueous solution. The reason for this is the immediate autoxidation of O2 adducts by water molecules. To achieve O2 binding in aqueous solution, the iron center of the porphyrin must be placed in a hydrophobic environment, wherefrom a water molecule is strictly excluded. Another essential requirement for a Mb model is the preparation of an electron-donative axial ligand that plays the role of proximal histidine (His). As an artificial O2 receptor that satisfies these challenging requirements, a supramolecule termed "hemoCD1" has been constructed. HemoCD1, a 1 : 1 inclusion complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(ii) (FeIITPPS) with a per-O-methylated ß-cyclodextrin dimer bearing a pyridine linker (Py3CD), reversibly binds O2 in aqueous solution at neutral pH and ambient temperature. The electronic spectra as well as the functions of hemoCD1 are analogous to those of Mb or its tetramer, hemoglobin (Hb). This is the first example of an artificial Hb/Mb biomimetic model capable of function in aqueous solution. Such a study on hemoCD1 as a Hb/Mb model has expanded research objectives to (1) syntheses of hemoCD1 analogues having distinct characteristics, (2) modeling enzymatic reactions of peroxidase, heme oxygenase, and cytochrome c oxidase in water, (3) development of fully synthetic artificial oxygen carriers (AOCs) utilized in animal blood, and (4) selective binding and removal of toxic small molecules, such as carbon monoxide (CO) and cyanide (CN-) in living organisms.

Effective Removal of Cyanide and Heavy Metals from an Industrial Electroplating Stream Using Calcium Alginate Hydrogels.

A real electroplating wastewater, containing 51,190 mg/L of free cyanide (CNf), 4899 mg/L of Ni and 1904 mg/L of Cu, was treated with calcium alginate hydrogel beads (CAB), pure or impregnated with biodegraded grape marc (EBGM) or activated carbon (EAC) in order to reduce the elevated load of toxic pollutants below the regulatory limits. It was evaluated the effect of increasing the amount of bioadsorbent as well as the influence of two successive adsorption cycles in the removal efficiency of pollutants. The most favourable sorption conditions onto CAB provided removal percentages of 85.02% for CNf and between 93.40-98.21% for heavy metals regarding the raw wastewater. The adsorption capacity of each pollutant onto CAB was considerably increased during the first 30 min of contact time, but after achieving the equilibrium, the following sorption capacities were obtained: 1177, 107.3, 39.5 and 1.52 mg/g for CNf, Ni, Cu and Zn, respectively. The kinetic adsorption of pollutants onto the CAB was adjusted to different kinetic models, observing that kinetic data agreed with the pseudo-second-order model. The information about intraparticle diffusion mechanisms in the bioadsorption process was also interpreted.

Toolkit Development for Cyanogenic and Gold Biorecovery Chassis Chromobacterium violaceum.

Chromobacterium violaceum has been of interest recently due to its cyanogenic ability and its potential role in environmental sustainability via the biorecovery of gold from electronic waste. However, as with many nonmodel bacteria, there are limited genetic tools to implement the use of this Gram-negative chassis in synthetic biology. We propose a system that involves assaying spontaneous antibiotic resistances and using broad host range vectors to develop episomal vectors for nonmodel Gram-negative bacteria. These developed vectors can subsequently be used to characterize inducible promoters for gene expressions and implementing CRISPRi to inhibit endogenous gene expression for further studies. Here, we developed the first episomal genetic toolkit for C. violaceum consisting of two origins of replication, three antibiotic resistance genes, and four inducible promoter systems. We examined the occurrences of spontaneous resistances of the bacterium to the chosen selection markers to prevent incidences of false positives. We also tested broad host range vectors from four different incompatibility groups and characterized four inducible promoter systems, which potentially can be applied in other Gram-negative nonmodel bacteria. CRISPRi was also implemented to inhibit violacein pigment production in C. violaceum. This systematic toolkit will aid future genetic circuitry building in this chassis and other nonmodel bacteria for synthetic biology and biotechnological applications.

Enhanced electro-generated ferrate using Fe(0)-plated carbon sheet as an anode and its online utilization for removal of cyanide.

Efficient electrochemical generation of ferrate (Fe(VI)) is still challenged by the passivation of iron materials. Herein, we employed Fe(0)-plated carbon sheet as an anode to enable an efficient production of Fe(VI) with its concentration reached up to 55 mM, which was 8 times higher than that with iron sheet of the same size as an anode. The SEM results showed that the close and uniform dispersion of tapered Fe(0) particles on the surface of carbon sheet helped prevent the formation of passivated layer. The preparative process of electro-deposited Fe(0) affected the generation of Fe(VI). The increase of electroplating time to 40 min and electroplating temperature to 30 °C promoted the production of Fe(VI), and the change in the concentration of Fe2+ in electroplated solution showed little impact on Fe(VI) generation. However, the addition of additives inhibited Fe(VI) generation. As well, an effective removal of cyanide was achieved using on-line production of Fe(VI), comparable to that by NaClO and higher than that by other traditional oxidants containing H2O2, O3, and KMnO4. This study would provide an simple and promising iron anode for efficient production of Fe(VI) by electrochemical method.

A Novel Thiophene-Based Fluorescent Chemosensor for the Detection of Zn2+ and CN-: Imaging Applications in Live Cells and Zebrafish.

A novel fluorescent turn-on chemosensor DHADC ((E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide) has been developed and used to detect Zn2+ and CN-. Compound DHADC displayed a notable fluorescence increase with Zn2+. The limit of detection (2.55 ± 0.05 µM) for zinc ion was far below the standard (76 µM) of the WHO (World Health Organization). In particular, compound DHADC could be applied to determine Zn2+ in real samples, and to image Zn2+ in both HeLa cells and zebrafish. Additionally, DHADC could detect CN- through a fluorescence enhancement with little inhibition with the existence of other types of anions. The detection processes of compound DHADC for Zn2+ and CN- were demonstrated with various analytical methods like Job plots, 1H NMR titrations, and ESI-Mass analyses.

Copper Complex-Embedded Vesicular Receptor for Selective Detection of Cyanide Ion and Colorimetric Monitoring of Enzymatic Reaction.

Detection of environmentally important ion cyanide (CN-) has been done by a new method involving displacement of both metal and indicator, metal indicator displacement approach (MIDA) on the vesicular interface. Terpyridine unit was selected as the binding site for metal (Cu2+), whereas Eosin-Y (EY) was preferred as an indicator. About 150 nm sized nanoscale vesicular ensemble (Lip-1.Cu) has shown good selectivity and sensitivity for CN- without any interference from other biologically and environmentally important anions. Otherwise, copper complexes are known for the interferences of binding with phosphates and amino acids. The Lip-1.Cu nanoreceptor also has the possibility to be used for real-time colorimetric scanning for the released HCN via enzymatic reactions. Lip-1.Cu has several superiorities over the other reported sensor systems. It has worked in 100% aqueous environment, fast response time with colorimetric monitoring of enzymatic reaction, and low detection limit.

Two-Step Elution Recovery of Cyanide Platinum Using Functional Metal Organic Resin.

A novel functional ion-exchange/adsorption metal organic resin (MOR), TEBAC-HKUST-1, was prepared and characterized. Ethanedithiol was used as the grafting agent to introduce thiol groups onto HKUST-1, and 4-vinylbenzyl chloride was then grafted onto SH-HKUST-1 using thiol groups. Finally, the quaternary ammonium functional group was immobilized onto the carrier by performing a quaternization reaction. The structure and property of TEBAC-HKUST-1 MOR were characterized by TGA, N2 adsorption-desorption, FTIR, SEM, and XRD. TEBAC-HKUST-1 MOR was used to remove metal cyanide complexes from wastewater. The adsorption was rapid, and the metal cyanide complexes including Pt(CN)42-, Co(CN)63-, Cu(CN)32-, and Fe(CN)63- were removed in 30 min. TEBAC-HKUST-1 MOR exhibited a high stability in neutral and weak basic aqueous solutions. Furthermore, Pt(II) could be efficiently recovered through two-step elution. The recovery rate of Pt(II) for five cycles were over 92.0% in the mixture solution containing Pt(CN)42-, Co(CN)63-, Cu(CN)32-, and Fe(CN)63-. The kinetic data were best fitted with the pseudo second-order model. Moreover, the isothermal data were best fitted with the Langmuir model. The thermodynamic results show that the adsorption is a spontaneous and exothermic process. TEBAC-HKUST-1 MOR not only exhibited excellent ability for the rapid removal of metal cyanide complexes, but also provided a new idea for the extraction of noble metals from cyanide-contaminated water.

Interaction-Transferable Graphene-Isolated Superstable AuCo Nanocrystal-Enabled Direct Cyanide Capture.

Noble metals with strong plasmons have been widely used as enhancement substrates for molecule identification. However, cyanide, a toxic and important signaling molecule with a corrosive nature to noble metals, makes direct recognition challenging. Herein a novel superstable magnetic graphene-isolated AuCo nanocrystal (MACG) has been designed. Such graphene isolation enables superior stability without corrosion. Moreover, unexpectedly, although graphene isolated direct contact between Au and cyanide, their interaction was transferable and remained, which gifted MACGs direct cyanide capture capability with no specific ligands needed. Density functional theory calculations and natural bond orbital analysis indicated that the graphene isolation only slightly affected the charge transfer and that a relatively strong interaction was maintained between Au and cyanide. MACGs were utilized for efficient cyanide capture and clearance in various hydrologic environments and sensitive in vivo cyanide capture in C. elegans infected with P. aeruginosa, a pathogen with cyanide as the biomarker, indicating promise for various applications.

Case Report of Lethal Toxin Lurking in an Edible Plant.

Cyanide is notoriously known to the public for more than a century now as a weapon of mass destruction (Zyklon B gas - hydrogen cyanide used by Nazis), an agent for chemical warfare during World War I (hydrogen cyanide) and very infamous "Suicide Pill" used in the past by military and espionage organizations during World War II (potassium cyanide). During the modern industrial era, cyanide poisoning is commonly associated with the industrial exposure and domestic fires. But there is little awareness about potentially fatal consequences of cyanide poisoning from common food sources. Here, we present the case report of a 79-year-old female with acute cyanide poisoning from improperly prepared cassava leaves. Symptoms from ingested toxin may start a few hours after exposure, which include headache, confusion, ataxia, seizures, palpitations, nausea, vomiting, abdominal pain, flushing, and itching of the skin. Patients may develop hypotension, cardiac arrhythmias, renal failure, hepatic necrosis, rhabdomyolysis, and metabolic acidosis; a multisystem manifestation of hypoxia at the cellular level. Multiple treatment strategies are available to treat cyanide poisoning, including sodium nitrite, sodium thiosulfate, and hydroxycobalamine. This is one of the scenarios where a thorough history, awareness of agents causing cyanide toxicity and knowledge of clinical manifestations can help avoid delays in prompt decision-making for appropriate treatment, thus reducing morbidity, mortality, and prolonged hospital course.

Highly Effective Removal of Metal Cyanide Complexes and Recovery of Palladium Using Quaternary-Ammonium-Functionalized MOFs.

In this study, quaternary-ammonium-functionalized metal⁻organic frameworks (MOFs) Et-N-Cu(BDC-NH2)(DMF), were prepared, characterized, and applied for the highly effective removal of metal cyanide complexes, including Pd(CN)4²-, Co(CN)6³-, and Fe(CN)6³-. Batch studies were carried out, and the maximum adsorption capacities of Pd(II), Co(III), and Fe(III) reached 172.9, 101.0, and 102.6, respectively. Adsorption was rapid, and equilibrium was established within 30 min. Et-N-Cu(BDC-NH2)(DMF) exhibited high thermal and chemical stability. Furthermore, absorbed Pd(CN)4²- was selectively recovered by two-step elution. First, Co(CN)6³- and Fe(CN)6³- were eluted with a 1.5 mol L-¹ KCl solution. Elution rates of Co(CN)6³- and Fe(CN)6³- were greater than 98.0%, whereas the elution percentage of Pd(CN)4²- was less than 2.0%. Second, >97.0% Pd(CN)4²- on the loaded MOFs was eluted using a 2.0 mol L-¹ KI solution. The recovery rate of Pd(CN)4²- was greater than 91.0% after five testing cycles. Adsorption isotherms, kinetics models, and adsorption thermodynamics of Pd(CN)4²- on Et-N-Cu(BDC-NH2) (DMF) were also systematically investigated. The Et-N-Cu(BDC-NH2) (DMF) absorbent exhibited a rapid, excellent ability for the adsorption of metal cyanide complexes.

Application of hybrid anaerobic reactor: Treatment of increasing cyanide containing effluents and microbial composition identification.

The study endeavors the anaerobic treatment of cyanide-containing effluents using the hybrid anaerobic reactor, with self-immobilized granules under high up-flow velocities. Comparison of one-year time-course analyses of HARs treating high strength effluents containing cyanide and control indicates the importance of wastewater characteristics in development and maintenance of microbiome. Efforts were directed towards associating process performance with microbial dynamics. Presence of cyanide results in the accumulation of intermediates paralleled with a drop in abundance of sensitive aceticlastic methanogens. HAR appear to have better resilience than other identified digesters because of shielding effects and enhanced granule-wastewater contact. The predominance of Methanobacteriales in the presence of cyanide can be linked to its tolerance. It was found that methane yield is positively correlated with abundance of aceticlastic guilds (R = 0.830, CI = 0.01). Tolerant bacterial groups were also identified. The study advances our knowledge related to less energy intensive technology with the focus on the development of efficient HAR.

Visual detection of cyanide ions by membrane-based nanozyme assay.

In this paper, we report a simple one-step synthesis of well-dispersed amorphous cobalt hydroxide/oxide-modified graphene oxide (CoOxH-GO) possessing peroxidase-like catalytic activity, and its application for the detection of H2O2, glucose, and CN- ions. CoOxH is formed and deposited in situ on the GO surface through the reaction between GO (size ~ 240nm) and Co2+ in basic solution at room temperature. We investigated the enzyme-mimicking activity of the CoOxH-GO nanohybrid in detail via the H2O2-mediated oxidation of Amplex Red (AR) to form fluorescent resorufin. The peroxidase-like activity of CoOxH-GO is utilized herein for the quantitation of H2O2 in a wide concentration range, from 100nM to 100µM. When coupled with glucose oxidase (GOD), the AR/CoOxH-GO system can determine glucose level in blood samples. Interestingly, cyanide ions (CN-) significantly inhibit the catalytic activity of the CoOxH-GO nanohybrid, which allows for the construction of a probe for the detection of CN- in water samples and laboratory wastes. We fabricated a membrane-based CoOxH-GO probe for the visual detection of CN- by preparing a thin film of CoOxH-GO on a positively charged and porous nylon membrane (N+M). The CoOxH-GO/N+M operates on the principle that CN- inhibits the catalytic activity of CoOxH-GO towards the H2O2-mediated oxidation of AR to form reddish resorufin on the membrane. The intensity of the red color of the membrane decreases with increasing CN- concentration, which can be easily observed with the naked eye at the nanomolar level. This cost-effective sensing system allows for the rapid and simple determination of the concentrations of CN- in complicated wastewater samples.

Anti-barnacle Activity of Isocyanides Derived from Amino Acids.

Creation of new potent antifouling active compounds is important for the development of environmentally friendly antifouling agents. Fifteen isocyanide congeners derived from proteinogenic amino acids were synthesized, and the antifouling activity and toxicity of these compounds against cypris larvae of the barnacle Balanus amphitrite were investigated. All synthesized amino acid-isocyanides exhibited potent anti-barnacle activity with EC50 values of 0.07 - 10.34 µg/ml after 120 h exposure without significant toxicity. In addition, seven compounds showed more than 95% settlement inhibition of the cypris larvae at 10 µg/ml after 120 h exposure without any mortality observed. Considering their structure, these amino acid-isocyanides would eventually be biodegraded to their original nontoxic amino acids. These should be useful for further research focused on the development of environmentally friendly antifoulants.

Chitosan-bound pyridinedicarboxylate Ni(II) and Fe(III) complex biopolymer films as waste water decyanidation agents.

Chitosan is a biopolymer with immense structural advantage for chemical and mechanical modifications to generate novel properties, functions and applications. This work depicts new pyridinedicarboxylicacid (PDC) crosslinked chitosan-metal ion films as veritable material for cyanide ion removal from aqueous solution. The PDC-crosslinked chitosan-metal films (PDC-Chit-Ni(II) and PDC-Chit-Fe(III)) were formed by complexing PDC-crosslinked chitosan film with anhydrous nickel(II) and iron(III) chloride salts respectively. The PDC-Chit and its metal films were characterized employing various analytical and spectroscopic techniques. The FT-IR, UV-vis and the XRD results confirm the presence of the metal ions in the metal coordinated PDC-crosslinked chitosan film. The surface morphological difference of PDC-Chit-Ni(II) film before and after decyanidation was explored with scanning electron microscopy. Furthermore, the quantitative amount of nickel(II) and iron(III) present in the complex were determined using Atomic Absorption Spectrophotometer as 32.3 and 37.2µg/g respectively which portends the biopolymer film as a good complexing agent. Removal of cyanide from aqueous solution with PDC-Chit, PDC-Chit-Ni(II) and PDC-Chit-Fe(III) films was studied with batch equilibrium experiments. At equilibrium, decyanidation capacity (DC) followed the order PDC-Chit-Ni (II)≈PDC-Chit-Fe(III)>PDC-Chit. PDC-Chit-Ni(II) film gave 100% CN(-) removal within 40min decyanidation owing to favorable coordination geometry.

Anodic oxidation of coke oven wastewater: Multiparameter optimization for simultaneous removal of cyanide, COD and phenol.

Anodic oxidation of industrial wastewater from a coke oven plant having cyanide including thiocyanate (280 mg L(-1)), chemical oxygen demand (COD - 1520 mg L(-1)) and phenol (900 mg L(-1)) was carried out using a novel PbO2 anode. From univariate optimization study, low NaCl concentration, acidic pH, high current density and temperature were found beneficial for the oxidation. Multivariate optimization was performed with cyanide including thiocyanate, COD and phenol removal efficiencies as a function of changes in initial pH, NaCl concentration and current density using Box-Behnken experimental design. Optimization was performed for maximizing the removal efficiencies of these three parameters simultaneously. The optimum condition was obtained as initial pH 3.95, NaCl as 1 g L(-1) and current density of 6.7 mA cm(-2), for which the predicted removal efficiencies were 99.6%, 86.7% and 99.7% for cyanide including thiocyanate, COD and phenol respectively. It was in agreement with the values obtained experimentally as 99.1%, 85.2% and 99.7% respectively for these parameters. The optimum conditions with initial pH constrained to a range of 6-8 was initial pH 6, NaCl as 1.31 g L(-1) and current density as 6.7 mA cm(-2). The predicted removal efficiencies were 99%, 86.7% and 99.6% for the three parameters. The efficiencies obtained experimentally were in agreement at 99%, 87.8% and 99.6% respectively. The cost of operation for degradation at optimum conditions was calculated as 21.4 USD m(-3).

A Highly Selective Sensor for Cyanide in Organic Media and on Solid Surfaces.

The application of IR 786 perchlorate (IR-786) as a selective optical sensor for cyanide anion in both organic solution (acetonitrile (MeCN), 100%) and solvent-free solid surfaces was demonstrated. In MeCN, IR-786 was selective to two anions in the following order: CN(-) > OH(-). A significant change in the characteristic dark green color of IR-786 in MeCN to yellow was observed as a result of nucleophilic addition of CN(-) to the fluorophore, i.e., formation of IR 786-(CN), which was also verified by a blue shift in the 775 nm absorbance peak to 430 nm. A distinct green fluorescence emission from the IR-786-(CN) in MeCN was also observed, which demonstrated the selectivity of IR-786 towards CN(-) in MeCN. Fluorescence emission studies of IR-786 showed that the lower detection limit and the sensitivity of IR-786 for CN(-) in MeCN was 0.5 µM and 0.5 to 8 µM, respectively. The potential use of IR-786 as a solvent-free solid state sensor for the selective sensing and monitoring of CN(-) in the environment was also demonstrated. On solvent-free solid state surfaces, the sensitivity of the IR-786 to CN(-) in water samples was in the range of 50-300 µM with minimal interference by OH(-).

An Evaluation of Sensor Performance for Harmful Compounds by Using Photo-Induced Electron Transfer from Photosynthetic Membranes to Electrodes.

Rapid, simple, and low-cost screening procedures are necessary for the detection of harmful compounds in the effluent that flows out of point sources such as industrial outfall. The present study investigated the effects on a novel sensor of harmful compounds such as KCN, phenol, and herbicides such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine (atrazine), and 2-N-tert-butyl-4-N-ethyl-6-methylsulfanyl-1,3,5-triazine-2,4-diamine (terbutryn). The sensor employed an electrode system that incorporated the photocurrent of intra-cytoplasmic membranes (so-called chromatophores) prepared from photosynthetic bacteria and linked using carbon paste electrodes. The amperometric curve (photocurrent-time curve) of photo-induced electron transfer from chromatophores of the purple photosynthetic bacterium Rhodobacter sphaeroides to the electrode via an exogenous electron acceptor was composed of two characteristic phases: an abrupt increase in current immediately after illumination (I0), and constant current over time (Ic). Compared with other redox compounds, 2,5-dichloro-1,4-benzoquinone (DCBQ) was the most useful exogenous electron acceptor in this system. Photo-reduction of DCBQ exhibited Michaelis-Menten-like kinetics, and reduction rates were dependent on the amount of DCBQ and the photon flux intensity. The Ic decreased in the presence of KCN at concentrations over 0.05 µM (=µmol·dm(-3)). The I0 decreased following the addition of phenol at concentrations over 20 µM. The Ic was affected by terbutryn at concentrations over 10 µM. In contrast, DCMU and atrazine had no effect on either I0 or Ic. The utility of this electrode system for the detection of harmful compounds is discussed.

Removal of cyanide compounds from coking wastewater by ferrous sulfate: Improvement of biodegradability.

The effect of ferrous sulfate (FeSO4) treatment on the removal of cyanide compounds and the improvement of biodegradability of coking wastewater were investigated by varying Fe:TCN molar ratios. Results suggested that the reaction between FeSO4 and coking wastewater was a two-step process. At the first step, i.e., 0≤Fe:TCN≤1.0, the reaction mechanisms were dominated by the precipitation of FeS, the complexation of CN(-), and the coagulation of organic compounds. The COD of coking wastewater decreased from 3748.1 mg/L to 3450.2 mg/L, but BOD5:COD (B/C) was improved from 0.30 to 0.51. At the second step, i.e., 1.0