Acrylonitrile Wastewater Research Articles

The Summary of the Methods to Acrylonitrile Wastewater Treatment

Acrylonitrile is widely used in chemical industry, mainly as raw materials to obtain acrylic fiber, nitrile rubber, ABS plastic and synthetic resins. However in the course of its production and uses, much colored organic wastewater will be released. Reducing COD and toxicity presents a challenge for the treatment. This paper focused on the introduction of acrylonitrile wastewater process and commented on patents of acrylonitrile wastewater removal technology. Furthermore, the advantages and disadvantages of the technologies were analyzed, and some suggestions were proposed.

Assessment of the Effects of Combined Fe/C Microelectrolysis–Electro-Fenton on the Acrylonitrile Removal from Analogue Wastewater

In the present work, acrylonitrile removal from analogue wastewater was investigated using the combined Fe/C microelectrolysis–electro-Fenton. The optimization parameters such as ratio of Fe/C, pH value, the reaction time, the dose of H2O2, the voltage, and the stir time on the acrylonitrile removal efficiency were determined by measuring the percentage removal of Chemical Oxygen Demand (CODcr) in the acrylonitrile analogue wastewater. In the Microelectrolysis section, the ratio of Fe/C was 1:1, the pH value was 3.0, and reaction time was 1h. In the electrolyzing Fenton, the optimal conditions of process parameters were the dose of H2O2 oxidant (5ml/L), the voltage (2.0 V), electrochemical reaction time (40min), and stir time (20min).Under the optimal conditions, the percentage removal of was 69% in first section and about 35% in the second section. Also, the dose of oxidant (H2O2) decreased from 11ml/L to 5ml/L compared with the using single active carbon method.

Removal of cyanide from acrylonitrile wastewater using gas membrane

Acrylonitrile wastewater is one of the most refractory industrial wastewaters as it contains cyanide at a high concentration. This study introduced a safe, effective and economic strategy, that is, use of the gas membrane to acrylonitrile wastewater treatment. Due to the complicated constituents of acrylonitrile wastewater, cyanide removal rate by gas membrane is very low. In order to enhance HCN removal, the operational conditions were optimized; pre-treatment strategies for fouling mitigation were also proposed and tested for acrylonitrile wastewater. The optimal operational parameters were achieved at an acidified pH of 5.0, wastewater velocity of 0.14 m s(-1), NaOH concentration of 10% and a temperature of 40 °C. The major factor affecting HCN removal was the pH of the acidified wastewater. The reason for the low removal rate was further explored and found to be the decrease of HCN transfer coefficient, which was caused by membrane fouling. Furthermore, the predominant foulants have been identified as colloidal organic materials and inorganic salts. Alkalization, which is effective in reducing these materials, has been proven to be most effective in mitigating membrane fouling and improving HCN removal, which was also confirmed by a pilot-scale study. The overall removal rate was therefore significantly enhanced to 87.1%.

Fouling and cleaning of gas-filled membrane for cyanide removal from acrylonitrile wastewater

Gas-filled membrane absorption process is a safe, effective and economic method for acrylonitrile wastewater treatment. However, membrane fouling is a serious problem affecting proper opera-tion of gas-filled membrane system. This study investigated the fouling characteristics in a 72 h continuously operating gas-filled membrane, and proposed an effective method to clean the membrane modules. In the gas-filled membrane system for acrylonitrile wastewater treatment, HCN transfer through gas-filled membrane stopped in two hours because of fouling. Cyanide removal rate achieved 82.0%. Permeation caused by hydrophilization occurred when gas-filled membrane absorption period was long enough, which led to operation failure of the whole treatment system. Inorganic fouling caused by Fe was found as the predominant reason. Four cleaning agents and three cleaning modes were applied for the fouled membrane to recovery mass transfer coefficient (K). The four-step cleaning (tap water-HCl-NaOH-EDTA) was recommended for the hydrophobic membrane system. The recovery of K value reached 95% for each cleaning cycle, which was confirmed in the pilot study as well. The results showed that it is feasible to reuse membrane modules during gas-filled membrane process for acrylonitrile wastewater treatment.

Acrylic wastewater treatment using SBR technology with aerobic granules

The acrylic or acrylonitrile wastewater treatment were investigated in experimental SBR systems with aerobic granules. The results showed that the diluted acrylic wastewater 400-800 mgL−1 could finally reach a COD removal 71.5-77.5% and a net COD removal 50.5–59.6%. The growth of aerobic granules in reactor was quite slow and retained MLSS 4.6-6.2 gL−1. The pretreatment by internal electrolysis was an effective way to remove cyanides and enhance the biodegradability of the wastewater. This combined SBR system achieved an approximately 70% COD removal. The post treatment by ozonation process was necessary to degrade the wastewater less than COD 130-143 mgL−1.

Synergetic effect of copper-plating wastewater as a catalyst for the destruction of acrylonitrile wastewater in supercritical water oxidation

A new supercritical water oxidation process for the simultaneous treatment of mixed wastewater containing wastewater from acrylonitrile manufacturing processes and copper-plating processes was investigated using a continuous tubular reactor system. Experiments were carried out at temperatures ranging from 400 to 600 °C and a pressure of 25 MPa. The residence time was fixed at 2 s by changing the flow rates of feeds, depending on reaction temperature. The initial total organic carbon (TOC) concentration of the wastewaters and the O 2 concentration at the reactor inlet were kept constant at 0.49 and 0.74 mol/L. It was confirmed that the copper-plating wastewater accelerated the TOC conversion of acrylonitrile wastewater from 17.6% to 67.3% at a temperature of 450 °C. Moreover, copper and copper oxide nanoparticles were generated in the process of supercritical water oxidation (SCWO) of mixed wastewater. 99.8% of copper in mixed wastewater was recovered as solid copper and copper oxides at a temperature of 600 °C, with their average sizes ranging from 150 to 160 nm. Our study showed that SCWO provides a synergetic effect for simultaneous treatment of acrylonitrile and copper-plating wastewater. During the reaction, the oxidation rate of acrylonitrile wastewater was enhanced due to the in situ formation of nano-catalysts of copper and/or copper oxides, while the exothermic decomposition of acrylonitrile wastewater supplied enough heat for the recovery of solid copper and copper oxides from copper-plating wastewater. The synergetic effect of wastewater treatment by the newly proposed SCWO process leads to full TOC conversion, color removal, detoxification, and odor elimination, as well as full recovery of copper.

Supercritical water oxidation of wastewater from acrylonitrile manufacturing plant

The wastewater from an acrylonitrile manufacturing plant, which is difficult to biodegrade, was decomposed in subcritical and supercritical water. Experiments were carried out at temperature ranging from 299 to 552 degrees C and a pressure of 25 MPa. The initial total organic carbon (TOC) of acrylonitrile wastewater was set from 0.27 to 2.10 mol L(-1) with residence times ranging from 3 to 30s. 30 wt.% H(2)O(2) solution was used as an oxidant with the stoichiometric ratios of O(2) based on the initial TOC concentration ranging from 0.5 to 2.5. TOC conversion increased with increasing reaction temperature and residence time, however, beyond the stoichiometric oxygen-TOC ratio of 1:1, TOC conversion was barely affected by excess oxygen. The initial TOC concentration of acrylonitrile wastewater also had a negligible effect on TOC conversion. An assumed pseudo-first-order global rate expression was determined with an activation energy of 53.48(+/-33.57)kJ mol(-1) and a pre-exponential factor of 5.22(+/-1.74)x10(2)s(-1). By considering the dependence of the reaction rate on TOC and O(2) concentration, a global rate expression was regressed from the complete set of 64 data points. The resulting activation energy was 66.33(+/-5.87)kJ mol(-1); the pre-exponential factor was 6.07(+/-6.89)x10(3)mol(-0.26)s(-1); and the reaction orders for initial TOC and O(2) concentration were 1.26(+/-0.15) and 0.00(+/-0.15), respectively.

Anaerobic Biochemical Treatment of Wastewater Containing Highly Concentrated Organic Cyanogen

The first and second stage of chilled wastewater in acrylic fibersitrile process and wastewater in acrylic fibers process are biodegraded under anaerobic conditions. Toxicity of acrylonitrile, acetonitrile, polymers, and cyanide in the wastewaters to the production of methane has been studied. Results suggest that the first and second stage chilled wastewaters from acrylonitrile process and wastewater from acrylic fibers process cannot be biodegraded well. CODBD of the first and second stage chilled wastewaters from acrylonitrile process is 36.3 and 45.8. CODBD of the wastewater from acrylic fibers process is 53.0. Acetonitrile, acrylonitrile, polymers, and cyanide are toxic to anaerobic bacteria in the highly concentrated organic cyanogens containing wastewater, inhibiting the methane-producing activity. Half inhibition concentration (50% IC) to anaerobic methane-producing activity is 1,300, 320, 85, and 50 mg/L for polymers, acetonitrile, acrylonitrile, and cyanide, respectively. Acrylonitrile is a metabolizing and physiological toxin, acetonitrile and polymers a metabolizing toxin, and cyanide a physiological and sterilizing toxin.

Activity of sulphate reducing bacteria according to COD/SO42- ratio of acrylonitrile wastewater containing high sulphate

This study was performed to evaluate the biodegradability of acrylonitrile wastewater, microbial inhibition effect of acrylonitrile wastewater on removal efficiency and the activity of sulphate reducing bacteria (SRB) according to COD/sulphate ratio. Acrylonitrile wastewater was hardly biodegradable in a biodegradability test, however, SRB activity was 57% for overall consumption of electron donor and it was relatively high value compared to 17% of reference test with glucose. COD removal of acrylonitrile wastewater was improved to 57% and 61% from 20% as the COD/sulphate ratio were 0.5 and 0.3 by sulphate addition to acrylonitrile wastewater. First order reaction rate constants k on organic removal of acrylonitrile wastewater were 0.001, 0.004 and 0.004 at each COD/sulphate ratio of 0.9, 0.5 and 0.3. Thus it was suggested that the activity of SRB was a significant factor for removing organics and sulphate simultaneously in acrylonitrile wastewater.

Biotreatment of acrylonitrile plant effluent by powdered activated carbon-activated sludge process

During powdered activated carbon-activated sludge (PAC-AS) treatment of acrylonitrile (ACN) plant wastewater, advantageous effects on COD reduction and specific respiration rate were observed. However, these advantages diminished gradually with prolonged operation. This can be attributed to the irreversible adsorption of some nonbiodegradable ACN wastewater components resulting in the inhibition of in situ bioregeneration of PAC.