Crude soybean peroxidase (SBP), isolated from soybean seed coats (hulls) at unusually low concentrations, catalyses the oxidative polymerisation of hazardous aqueous benzidine and its 3,3′-dichloro, 3,3′-dimethyl and 3,3′-dimethoxy derivatives in the presence of hydrogen peroxide. The optimum operating conditions for oxidation of 0·10 mM benzidine were investigated. At pH 5, the hydrogen peroxide-to-substrate concentration ratio was 1·5 and the minimum SBP concentration required to achieve at least 95% conversion of the benzidine in synthetic wastewater was 0·43 mU/ml. Progress curves were established for the conversion of the four substrates, and apparent first-order rate constants were derived. Enzyme-catalysed polymerisation with SBP and subsequent removal of the polymeric products generated can provide an alternative means to conventional methods for treating many aromatic wastewater pollutants, including the benzidines studied here.

Background. Some industrial manufacturing processes generate and release dyes as water pollutants, many of which are toxic and hazardous materials. There is a need for milder, greener methods for dye treatment. Objectives. The objective of the present study was to investigate and optimize azo dye decoloration by a crude soybean peroxidase (SBP), based on two dyes that have widespread industrial use, but that differ greatly in structural complexity, Acid Black 2 and Acid Orange 7, and to investigate the effects of specific parameters on the removal process. Methods. Batch reactors were used to remove 95% of the dyes' color and to produce substantial precipitates. Results. The optimum pH for enzymatic decoloration of Acid Black 2 was in the acidic region, pH 4.4, and that of Acid Orange 7 occurred under neutral conditions, pH 6.9. The minimum enzyme activity needed for sufficient removal was 1.2 U/mL for both dyes at 0.5 mM. The minimum molar hydrogen peroxide/substrate ratio was 3 for Acid Orange 7 and 2.5 for Acid Black 2 to achieve approximately 95% removal. First-order fitting of progress curve data collected under the respective optimum conditions gave half-lives of 23.9 and 28.9 minutes for Acid Orange 7 and Acid Black 2, respectively. Conclusions. The feasibility of SBP-catalyzed treatment of industrial dyes Acid Black 2 and/or Acid Orange 7, or dyes that resemble them, as they might occur in industrial effluents, was successfully demonstrated. Competing Interests.The authors declare no competing financial interests

Benzidines and phenols are the most priority pollutants. Separation and quantitative estimation of priority pollutant benzidines composed of various benzidines BZ, including substituted 3, 3'-dichlorobenzidine DCB and 3, 3'-dimethylbenzidine DMB, and priority pollutant phenols (9 compounds, i.e., phenol, 2-and 4-nitrophenol, 2,4-dimethylphenol, 2-, 2,4-di-, 2,4,6-tri-, Penta-chlorophenol, and 4-chloro-3-methylphenol)was performed using high performance liquid chromatography-ultra violet techniques. Both groups were separated using a C-18 column with a UV detector at a wavelength of 280 nm, and the flow of the mobile phase was isocratic. The mobile phase consisted of 75:25 methanol: water. The column temperature was 50°C, and the flow rate was 1.8 ml/min for the Benzedine's separation. The mobile phase consisted of a 50:50 acetonitrile: phosphate buffer. The optimum pH was 7.1, the flow rate was 0.7 ml/min and the optimum column temperature was 45°C for the phenols separation. The separation parameters were calculated, including the chromatographic parameters such as the capacity factor (k), the number of theoretical plates (N) , the selectivity factor (α), and the resolution factors (Rs).This method was applied to real samples. The water samples that were analyzed were obtained from a petroleum refinery wastewater treatment unit. The results ranged between undetectable levels and 246.9μg/L of the selected benzidines.The results were ranged between undetectable levels and 1865.61 μg/L of the selected phenols.

Two simple methods for the determination of eugenol were developed. The first depends on the oxidative coupling of eugenol with p-amino-N,N-dimethylaniline (PADA) in the presence of K3[Fe(CN)6]. A linear regression calibration plot for eugenol was constructed at 600 nm, within a concentration range of 0.25-2.50 μg.mL–1 and a correlation coefficient (r) value of 0.9988. The limits of detection (LOD) and quantitation (LOQ) were 0.086 and 0.284 μg.mL–1, respectively. The second method is based on the dispersive liquid-liquid microextraction of the derivatized oxidative coupling product of eugenol with PADA. Under the optimized extraction procedure, the extracted colored product was determined spectrophotometrically at 618 nm. A linear plot within a concentration range of 0.05–1.65 μg.mL–1 (r = 0.9997) was constructed. The LOD and LOQ were 0.053 and 0.177 μg.mL–1, respectively. Both methods were tested for the analysis of eugenol in commercial personal-care products, and the results confirmed that the procedures are accurate, precise, and reproducible (RSD < 1%).