Cyanide In Wastewater Research Articles

Investigation on adsorption performance of mesoporous activated biomass prepared from <i>Cocos nucifera</i> husk for harzadous cyanide wastewater treatment

The influence of various factors namely pH, absorbent dosage; contact time and initial ion concentration was studied to identify the adsorption capacity of the adsorbent. The optimum pH was obtained at pH =3 for all the adsorbent. Other physiochemical parameters, ranging from the surface area to the scanning electron microscope (SEM) were studied and indicate that the cocos nucifera husk is a good precursor for investigation on activated biomass for hardzadous cyanide wastewater. Adsorption data were modeled using Langmuir, Freundlich, Temkin, Henry and Harkin Jura equation. Henry with the correlation coefficient R2 0.875 had a better fit than Freundlich which is R2= 0.836, Temkin; R2= 0.875, Langmuir; R2= 0.742 and Harkin Jura which is R2= 0.471 with maximum monolayer saturation capacity of cyanide ions adsorbed per gram of activated Cocos nucifera husk. Equibrium data were best described by Henry model. Kinetic models were also carried out including pseudo first order with R2= 0.969, Pseudo-second order R2 = 0.998,Intra-particle diffusion R2 = 0.909, and Elovich Kinetic model with R2 of 0.814, the kinetic data were best described and seen by Pseudo second order model. It is then proven that the study of the entire adsorbent are most efficient for the removal of cyanide from waste waters and it can be used as low-cost adsorbent for the removal of cyanide ions from wastewater.

Enrichment of copper and recycling of cyanide from copper–cyanide waste by solvent extraction

The enrichment of copper from copper–cyanide wastewater by solvent extraction was investigated using a quaternary ammonium salt as an extractant. The influences of important parameters, e.g., organic-phase components, aqueous pH values, temperature, inorganic anion impurities, CN/Cu molar ratio, and stripping reagents, were examined systematically, and the optimal conditions were determined. The results indicated that copper was effectively concentrated from low-concentration solutions using Aliquat 336 and that the extraction efficiency increased linearly with increasing temperature. The aqueous pH value and concentrations of inorganic anion impurities only weakly affected the extraction process when varied in appropriate ranges. The CN/Cu molar ratio affected the extraction efficiency by changing the distribution of copper–cyanide complexes. The difference in gold leaching efficiency between using raffinate and fresh water was negligible.

Optimization of cyanide extraction from wastewater using emulsion liquid membrane system by response surface methodology.

To solve the disposal problem of cyanide wastewater, removal of cyanide from wastewater using a water-in-oil emulsion type of emulsion liquid membrane (ELM) was studied in this work. Specifically, the effects of surfactant Span-80, carrier trioctylamine (TOA), stripping agent NaOH solution and the emulsion-to-external-phase-volume ratio on removal of cyanide were investigated. Removal of total cyanide was determined using the silver nitrate titration method. Regression analysis and optimization of the conditions were conducted using the Design-Expert software and response surface methodology (RSM). The actual cyanide removals and the removals predicted using RSM analysis were in close agreement, and the optimal conditions were determined to be as follows: the volume fraction of Span-80, 4% (v/v); the volume fraction of TOA, 4% (v/v); the concentration of NaOH, 1% (w/v); and the emulsion-to-external-phase volume ratio, 1:7. Under the optimum conditions, the removal of total cyanide was 95.07%, and the RSM predicted removal was 94.90%, with a small exception. The treatment of cyanide wastewater using an ELM is an effective technique for application in industry.

Ozonation in water treatment: the generation, basic properties of ozone and its practical application

AbstractThe widespread applications of ozone technologies are established on the basis of large-scale manufacture of ozone generator and chemical reactivity of ozone. It is hence necessary to summarize the principles of ozone generation and to analyze the physicochemical properties of ozone, which are of fundamental significance to indicate its technical developments and practical applications. This review presents a summary concerning ozone generation mechanisms, the physicochemical properties of ozone, as well as the applications of ozone in water treatment. Ozone can be produced by phosphorus contact, silent discharge, photochemical reactions, and electrochemical reactions, principally proceeding by the reaction of oxygen atom with oxygen molecule. There are side reactions to the generation of ozone, however, which are responsible for ozone depletion including thermal decomposition and quenching reactions by reactive species. The solubility of ozone in water is much higher than that of oxygen, suggesting that it may be reliably applied in water and wastewater treatment. Based on the resonance structures of ozone, one oxygen atom in ozone molecule is electron-deficient displaying electrophilic property, whereas one oxygen atom is electron-rich holding nucleophilic property. The superior chemical reactivity of ozone can also be indirectly revealed by radical-mediated reactions initiated from homogenous and heterogeneous catalytic decomposition of ozone. Owing to the reliable generation of ozone and its robust reactive properties, it is worthy to thoroughly elaborate the applications of ozone reaction in drinking water disinfection and pre- or post-treatment of industrial wastewater including cyanide wastewater, coking wastewater, dyeing wastewater, and municipal wastewater. The structural characteristics of ozone reactors and energy requirement of applied technologies are evaluated. In addition, future directions concerning the development of ozone generation, ozone reactivity, and industrial wastewater ozonation have been proposed.

Assessment of the toxicity of wastewater from the metalworking industry treated using a conventional physico-chemical process.

This article presents results from a toxicity reduction evaluation program intended to describe wastewater from the metalworking industry that was treated using a conventional physico-chemical process. The toxicity of the wastewater for the microcrustacean Daphnia magna was predominantly expressive. Alkaline cyanide wastewater generated from electroplating accounted for the largest number of samples with expressive toxicity. When the raw wastewater concentrations in the batches were repeated, inexpressive toxicity variations were observed more frequently among the coagulated-flocculated samples. At the coagulation-flocculation step, 22.2% of the treatments had reduced acute toxicity, 30.6% showed increased toxicity, and 47.2% remained unchanged. The conductivity and total dissolved solids contents of the wastewater indicated the presence of salts with charges that were inappropriate for the survival of daphnid. The wastewaters treated by neutralization and coagulation-flocculation had average metallic compound contents that were greater than the reference toxic concentrations reported in other studies, suggesting that metals likely contributed to the toxic effects of the wastewater on freshwater microcrustaceans. Thus, alternative coagulants and flocculants should be assessed, and feasible doses should be determined to improve wastewater treatment. In addition, advanced treatment processes should be assessed for their abilities to remove dissolved toxic salts and ions.

A Feasible Strategy for Calculating the Required Mass Transfer Height of a New Bubbling Organic Liquid Membrane Extraction Tower Directly Based upon the Experimental Kinetic Data

Extraction and recovery of gold(I) with extremely low concentration in cyanide wastewater were conducted as an example aimed to develop a feasible method based upon the experimental kinetic data for calculating the required mass transfer height of a new bubbling organic liquid membrane extraction tower. The kinetic extraction equation based on curve fitting the experimental c(t) ∼ t data from single column extraction could be established to describe the quantitative relationship of the concentration change of gold(I) in flowing-out aqueous solution from the tower with the reaction time in the tower, so that the required tower height involved in the axial gas mixing effect could be calculated from the residence time of the aqueous solution passing through the tower to achieve a target equilibrating concentration. The influence of organic phase recycling on the calculation was discussed. Double column extraction experiments confirmed that the suggested calculation method obtained from single column extraction is reasonable. The present work is in favor of understanding the mass transferring kinetic behaviors of target components in that suggested bubbling extraction tower, and it highlights a feasible strategy directly from the experimental kinetic data to calculate the required mass transferring height of the tower for its structure design, optimization, and scale-up, and provides fundamental data for future industrial application of the tower to extract and recover other heavy metal ions from wastewater.

Preparation of La-TiO2/Bentonite and Its Photodegradation Properties to Cyanide.

The photocatalytic materials were prepared by sol-gel method: the main raw materials were tetrabutyltitanate and the lanthanum nitrate hexahydrate, bentonite was the carrier to support TiO2. The properties of the composites were characterized by specific surface area (BET), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). The photocatalytic degradation of cyanide waste water was used to assess the photocatalytic activity of the materials. The experimental results showed that the suitable content of lanthanum and roasted temperature could improve the photocatalytic activity. When the composites were roasted at 400 °C and the molar ratio of La to Ti was 1%, the photocatalyst reached optimal performance.

Application of carbon foam for heavy metal removal from industrial plating wastewater and toxicity evaluation of the adsorbent

Electroplating wastewater contains various types of toxic substances, such as heavy metals, solvents, and cleaning agents. Carbon foam was used as an adsorbent for the removal of heavy metals from real industrial plating wastewater. Its sorption capacity was compared with those of a commercial ion-exchange resin (BC258) and a heavy metal adsorbent (CupriSorb™) in a batch system. The experimental carbon foam has a considerably higher sorption capacity for Cr and Cu than commercial adsorbents for acid/alkali wastewater and cyanide wastewater. Additionally, cytotoxicity test showed that the newly developed adsorbent has low cytotoxic effects on three kinds of human cells. In a pilot plant, the carbon foam had higher sorption capacity for Cr (73.64 g kg−1) than for Cu (14.86 g kg−1) and Ni (7.74 g kg−1) during 350 h of operation time. Oxidation pretreatments using UV/hydrogen peroxide enhance heavy metal removal from plating wastewater containing cyanide compounds.

Treatment of cyanide wastewater by bulk liquid membrane using tricaprylamine as a carrier.

The transport of cyanide from wastewater through a bulk liquid membrane (BLM) containing tricaprylamine (TOA) as a carrier was studied. The effect of cyanide concentration in the feed solution, TOA concentration in the organic phase, the stirring speed, NaOH concentration in the stripping solution and temperature on cyanide transport was determined through BLM. Mass transfer of cyanide through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters (k(1), k(2), R(m)(max), t(max), J(a)(max), J(d)(max)) were also calculated. Apparently, increase in membrane entrance (k(1)) and exit rate (k(2)) constants was accompanied by a rise in temperature. The values of activation energies were obtained as 35.6 kJ/mol and 18.2 kJ/mol for removal and recovery, respectively. These values showed that both removal and recovery steps in cyanide transport is controlled by the rate of the chemical complexation reaction. The optimal reaction conditions were determined by BLM using trioctylamine as the carrier: feed phase: pH 4, carrier TOA possession ratio in organic phase: 2% (V/V), stripping phase concentration of NaOH: 1% (W/V), reaction time: 60 min, stirring speed: 250 r/min. Under the above conditions, the removal rate was up to 92.96%. The experiments demonstrated that TOA was a good carrier for cyanide transport through BLM in this study.

Comparing the efficacy of VUV and [formula omitted] advanced oxidation processes for degradation and mineralization of cyanide in wastewater

The present study was designed to evaluate cyanide degradation and mineralization in an industrial wastewater by vacuum ultraviolet (VUV) and ultraviolet/persulfate (UVC/S2O82-) advanced processes. The effect of operational conditions such as cyanide concentration, air/O2 blowing, reaction time, S2O82- concentration, and presence of Cr(VI) were studied. The possible intermediates of the reaction were also tracked. It was observed that under optimal condition, complete destruction of 50mg/L cyanide was reached in 15min and 50min for VUV-air and UVC/S2O82- processes, respectively. Tracking of the generated by-products revealed that VUV and UVC/S2O82- processes completely oxidized and mineralized cyanide to much less noxious compounds, mainly ammonia and carbonate. Application of VUV process for chromium electroplating wastewater (68mg/L cyanide and 24mg/L Cr(VI)) showed that complete oxidation of cyanide along with 72% reduction of Cr(VI) to Cr(III) was reached in a short reaction time of 18min. Accordingly, the homogenous VUV advanced process was found to be an efficient chemical-less method appropriate for simultaneous oxidation of cyanide and reduction of Cr(VI) in industrial wastewater.

Isolation of high-salinity-tolerant bacterial strains, Enterobacter sp., Serratia sp., Yersinia sp., for nitrification and aerobic denitrification under cyanogenic conditions.

Cyanides (CN(-)) and soluble salts could potentially inhibit biological processes in wastewater treatment plants (WWTPs), such as nitrification and denitrification. Cyanide in wastewater can alter metabolic functions of microbial populations in WWTPs, thus significantly inhibiting nitrifier and denitrifier metabolic processes, rendering the water treatment processes ineffective. In this study, bacterial isolates that are tolerant to high salinity conditions, which are capable of nitrification and aerobic denitrification under cyanogenic conditions, were isolated from a poultry slaughterhouse effluent. Three of the bacterial isolates were found to be able to oxidise NH(4)-N in the presence of 65.91 mg/L of free cyanide (CN(-)) under saline conditions, i.e. 4.5% (w/v) NaCl. The isolates I, H and G, were identified as Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Results showed that 81% (I), 71% (G) and 75% (H) of 400 mg/L NH(4)-N was biodegraded (nitrification) within 72 h, with the rates of biodegradation being suitably described by first order reactions, with rate constants being: 4.19 h(-1) (I), 4.21 h(-1) (H) and 3.79 h(-1) (G), respectively, with correlation coefficients ranging between 0.82 and 0.89. Chemical oxygen demand (COD) removal rates were 38% (I), 42% (H) and 48% (G), over a period of 168 h with COD reduction being highest at near neutral pH.

Effect of lanthanum-doped amount on photocatalytic activity of TiO<SUB align="right">2/bentonite in cyanide waste water

The photocatalysts prepared by the primary materials of butyl titanate and bentonite, containing the dopant lanthanum in amounts from 0 to 3% (molar ratio of lanthanum to titanium) were used in a low concentration of cyanide waste water to detect the performance. They were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric apparatus (TG) and EDS analysis to obtain some properties. When the lan-doped amount was about 1%, the photocatalyst was more effective in photocatalytic degradation. The work indicated that the moderate lanthanum was effective in degrading cyanide waste water and the optimal amount was 1%.

Effect of lanthanum-doped amount on photocatalytic activity of TiO<SUB align="right">2/bentonite in cyanide waste water

Effect of lanthanum-doped amount on photocatalytic activity of TiO<SUB align="right">2/bentonite in cyanide waste water

Adsorption Technology and Mechanism of Cu and CN− From Cyanide Waste Water on Modified Peanut Shell

Modified peanut shell (MPS) was prepared from peanut hull by chemical activation with H3PO4 and carbonized, which was characterized by micrometrics ASAP-20, SEM, and EDS. Adsorption of Cu and CN− on MPS was investigated as a function of pH, adsorbent dosage, temperature and time. The Langmuir and Freundlich models were used to simulate the adsorption isotherms of Cu at different temperature. The thermodynamic date were calculated, the results suggest that adsorption process of Cu on MPS was spontaneous and endothermic. Pseudo second-order kinetic model fits the experimental curves of Cu well and adsorption curve of CN− fits the pseudo first-order kinetic model.

Recovery Cyanide from Cyanide-Containing Wastewater By Selective Electroconcentration

A large amount of hydrogen cyanide poisonous gases released from Polyacrylonitrile（PAN）-basis carbon fiber manufacturing process. Stimulated by its value and harmfulness to human and environment, electrochemical methods have proposed to deal with the double-edged materials. A novel electrodeionization technology, named as selective electroconcentration (SEC), was used to segregate targeted ions from mixed aqueous solution. SEC is an approach not only removes needless ions，but also obtains concentrated ions in brine water. In this paper, synthetic water contained cyanide and carbonate was investigated to examine the separation and enrichment effects of SEC. It was found that the pH raise in divalent ions concentrated chamber prevented carbonate conversion, which avoided bicarbonate competing with cyanide. Thus monovalent ions were able to migrate to next concentrated chamber. To acquire details about how to optimize the SEC apparatus, operation parameters like current, pH change, and proportion were discussed here. Practical results show that cyanide purity can reach 90%, with a high cyanide concentration (250mmol/L). The cyanide product can be used as plating solution. Beyond that, the concentration of treated cyanide wastewater conformed sewage discharge standard. It is proved that SEC is feasible to concentrate cyanide and the separation efficiency is satisfactory.

Study of cyanide wastewater treatment by dispersion supported liquid membrane using trioctylamine and kerosene as liquid membrane.

A certain amount of cyanide is present in wastewater of various industrial processes, such as wet extraction of gold, coal processing, electroplating and other industries. In this work, an experimental study regarding transport of cyanide through a dispersion supported liquid membrane was performed. A model was established to describe the reaction and transport of CN(I) in the supported liquid membrane and the mass transfer kinetics equations were deduced. Through mass transfer kinetic equation it was derived that, when the carrier concentration was under certain conditions, there was a linear relationship between the reciprocal of the permeability coefficient of CN(I) (1/Pc) and n-th power of the concentration of H+ (cnH+), and the parameters Δa(δa/da) and Δo(δ0/d0) could be obtained from the slope and intercept of the straight line. Then the diffusion coefficient do and the diffusion layer thickness δo of the phase interface between the feed phase and membrane phase could be calculated. Factors affecting migration of CN(I) were analyzed, and the stable removal rate of CN(I) was more than 90% with carrier concentration (%TOA) of 2%, feed phase pH of 4, initial CN(I) concentration of 30 mg/L, stirring time of 1 hour, volume ratio of membrane solution to NaOH solution of 2:1, strip phase concentration of 2 mol/L. The results showed that the overall mass transfer rate increased first and then decreased with an increase of TOA concentration, organic-to-strip volume ratio, and strip concentration. Furthermore, the transport percentage of CN(I) was increased, the stability of membrane was enhanced, and the lifetime of the membrane was extended.

Efficient removal of heavy metals from electroplating wastewater using polymer ligands

Poly(hydroxamic acid)-poly(amidoxime) chelating ligands were synthesized from poly(methyl acrylate-co-acrylonitrile) grafted acacia cellulose for removing toxic metal ions from industrial wastewaters. These ligands showed higher adsorption capacity to copper (2.80 mmol·g−1) at pH 6. In addition, sorption capacities to other metal ions such as iron, zinc, chromium, and nickel were also found high at pH 6. The metal ions sorption rate (t1/2) was very fast. The rate of adsorption of copper, iron, zinc, chromium, nickel, cobalt, cadmium and lead were 4, 5, 7, 5, 5, 8, 9 and 11 min, respectively. Therefore, these ligands have an advantage to the metal ions removal using the column technique. We have successfully investigated the known concentration of metal ions using various parameters, which is essential for designing a fixed bed column with ligands. The wastewater from electroplating plants used in this study, having chromium, zinc, nickel, copper and iron, etc. For chromium wastewater, ICP analysis showed that the Cr removal was 99.8% and other metal ions such as Cu, Ni, Fe, Zn, Cd, Pb, Co and Mn removal were 94.7%, 99.2%, 99.9%, 99.9%, 99.5%, 99.9%, 95.6% and 97.6%, respectively. In case of cyanide wastewater, the metal removal, especially Ni and Zn removal were 96.5 and 95.2% at higher initial concentration. For acid/alkali wastewater, metal ions removing for Cd, Cr and Fe were 99.2%, 99.5% and 99.9%, respectively. Overall, these ligands are useful for metal removal by column method from industrial wastewater especially plating wastewater.

Statistical Enhancement of Cyanide Degradation Using Microbial Consortium

Remediation of cyanide contaminated water bodies using microorganisms is a popular alternative over chemical and physical methods of cyanide detoxification. The objective of the present study is to develop a microbial consortium using three bacteria, i.e., Enterobacter sp. RL2a, Serratia marcescencs RL2b and Achromobacter sp. RL2c for effective degradation of simulated cyanide wastewater. In vitro cyanide degradation was optimum with 2% inoculum volume of cells; pH 6.0, 30°C temperature at 20 mM substrate concentration leading to complete cyanide removal in 36 h. Response surface methodology (RSM) approach was used for optimization of reaction conditions for cyanide degradation using 5 mg ml-1 resting cells of microbial consortium. Plackett-burman design depicted that three variables viz. time, resting cells of strain RL2b and pH exhibit positive effect on cyanide degradation. The analysis of the quadratic regression model suggested that the model was very significant as correlation coefficient (0.847) closer to 1 denotes better correlation between the observed and predicted responses. The model was validated by performing the experiment under optimum conditions, which resulted in 63% cyanide degradation in 1 h reaction and complete degradation of 20 mM cyanide in 6 h. By performing factorial design, there was 1.3 fold (33%) increases in cyanide degradation.

Photocatalytic degradation of cyanide in wastewater using new generated nano-thin film photocatalyst

This study investigates the possibility of using new generated potassium lanthanum titanates (K2La2Ti3O10, KLTO) photocatalyst thin films and CeO2 buffer layer produced using sol–gel method to remove cyanide from wastewater. DTA–TG, FTIR, XRD, XPS, SEM, AFM and profilometer analyses were performed to determine the thermal, structural and morphological characterization of the thin film photocatalysts, respectively. In order to provide the highest photocatalytic activity, new generated photocatalytic films with KLTO/CeO2 architecture were coated on Si (100) substrates and the cyanide degradation experiments were carried out. In this respect, initial concentration, pH of cyanide and light intensity were chosen as variables and their single and joint effects on removal of cyanide from wastewater were investigated. ATLAS Suntest CPS+ which simulates solar radiation was used as illumination source for the photocatalytic degradation of cyanide. ANOVA statistical test was carried out to understand the effectiveness of the variables. The degradation experiments were fitted to first order reaction law. The maximum degradation efficiency of cyanide was found to be 99.87% at pH of 10 and light intensity of 750W/m2 by using 100mg/l cyanide initial concentration after 5hour irradiation.

Biodetoxification of cyanide-containing industrial wastewaters by Rhodococcus UKMP-5M

The utilization of cyanide in many industrial processes despite its toxicity generated voluminous effluents, which necessitated treatment prior to discharge into the environment. In the present study, Rhodococcus UKMP-5M was solely employed as biological tool to detoxify three different cyanide-containing industrial wastewaters with different characteristics since initial attempt to employ mixed culture of Rhodococcus strains was unsuccessful due to synergistic interaction which yielded only 19% biodetoxification of 12 mM cyanide. The bacterium was able to achieve 97% cyanide removal efficiency in Wastewater A (pH 8.4) after 19 days of incubation. However, the growing cells needed the supplementation of nutrients, which was uneconomical besides requiring extensive time for complete detoxification. In contrast, the employment of immobilized beads of Rhodococcus UKMP-5M, which required a relatively straightforward method, were cost-effective in detoxifying almost 100% of 15 mM cyanide in Wastewater C (pH 9.5) within a short period of 3 days of incubation. This discovery is highly significant since most wastewaters pHs originating from various industrial applications involving cyanide often range from 6 to 9.5 and this strain is therefore seemingly effective for biodetoxification of cyanide-containing wastewaters with high pH values. In addition, it is interesting to note that the presence of heavy metals in the wastewaters did not inhibit the cyanide-degrading activity of the bacterium. The findings from this study provided essential information to develop a pilot plant on a technical scale for the biotreatment of industrial effluents bearing cyanide, which should be of great interest from an environmental and economic point of views.