HORSERADISH PEROXIDASE CATALYZED DEGRADATION OF BROMOPHENOL BLUE DYE

In this study, the oxidative destruction of bromophenol blue dye with hydrogen peroxide was carried out at pH 4.0-4.1 in the presence of a commercial horseradish peroxidase, as well as peroxidase isolated directly from horseradish roots (Armoracia rusticana). To determine peroxidase activity, a model reaction of the oxidation of phenol to quinone was used. With a dye concentration of 32.7 μM, the optimal concentration of hydrogen peroxide was 0.04 mM at peroxidase concentration of 1.15 nM. The optimal temperature of the enzymatic reaction was determined: at 23 °С for 10 min 90% of the dye was exposed to destruction. When the temperature rises to 50 °С, the reaction rate decreases, and the degree of destruction is 56% for the same time interval. It was shown that the initial rate of peroxidase oxidation of bromophenol blue follows Michaelis-Menten equation. The kinetic parameters of the enzymatic reaction were determined by linearizing Michaelis-Menten equation in Lineweaver-Burk coordinates. It was found that for the peroxidase oxidation reaction of bromophenol blue Michaelis constant and maximum rate were 42.7 μM and 57.5 μM·min–1, respectively. In this work, а high percentage of dye degradation was also achieved when using peroxidase isolated from horseradish roots. The experiments were conducted at a temperature of 30оС and pH 4.1. With the increase in the volume of the extract from 0.1 to 0.2 ml, the percentage decolorization increases from 75% to 90%. The results demonstrate the high degradation efficiency of bromophenol blue with the participation of the commercial horseradish peroxidase and peroxidase isolated from horseradish roots. Enzymatic oxidative degradation can be considered as an alternative to biodegradation.

Biogenic and chemically synthesized Solanum tuberosum peel–silver nanoparticle hybrid for the ultrasonic aided adsorption of bromophenol blue dye

This work was aimed at the synthesis of a hybrid (STpe-AgNP), obtained by impregnation of silver nanoparticles (AgNP) onto Solanum tuberosum peel (STpe), for the ultrasonic assisted adsorption of bromophenol blue (BB) dye. SEM, FTIR, XRD, EDX, TGA and BET techniques were used to characterize the adsorbents. The XRD, SEM and EDX confirmed successful impregnation of AgNPs onto STpe to form the hybrid. The AgNPs impregnated onto the hybrid were found to be water stable at various pH values of 2.0–9.0. Chi-square (χ2 < 0.024) and linear regression (R2 > 0.996) showed that the Freundlich model was best fitted among the isotherm models, corroborated by the oriented site model. Kinetic analysis conformed to the intraparticle diffusion and pseudo-first-order rate equations, while thermodynamics displayed a physical, spontaneous and endothermic adsorption process. The presence of competing Pb(II), Ni(II), Cd(II) and Zn(II) metal ions in solution interfered with the adsorption of BB onto the biosorbents. In terms of reusability, STpe and STpe-AgNP showed BB desorption of 91.3% and 88.5% respectively, using NaOH as eluent. Ultra-sonication significantly enhanced the adsorption of BB by both adsorbents, but the impregnation of AgNPs only slightly improved adsorption of the dye from the simulated wastewater. This study also illustrated that pristine STpe biomass waste is a cheap viable option for the decontamination of BB from water.