Biodegradation of 2,4-dinitrophenol with laccase immobilized on nano-porous silica beads
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IRANIAN JOURNAL OF ENVIRONMENTAL HEALTH SCIENCE & ENGINEERING
RESEARCH ARTICLE
Open Access
Biodegradation of 2,4-dinitrophenol with laccase immobilized on nano-porous silica beads Emad Dehghanifard1, Ahmad Jonidi Jafari2,3*, Roshanak Rezaei Kalantary1,4, Amir Hosein Mahvi1,3, Mohammad Ali Faramarzi5 and Ali Esrafili1
Abstract Many organic hazardous pollutants, including 2,4-dinitrophenol (2,4-DNP), which are water soluble, toxic, and not easily biodegradable make concerns for environmental pollution worldwide. In the present study, degradation of nitrophenols-contained effluents by using laccase immobilized on the nano-porous silica beads was evaluated. 2,4-DNP was selected as the main constituent of industrial effluents containing nitrophenols. The performance of the system was characterized as a function of pH, contact time, temperature, pollutant, and mediator concentrations. The laccase-silica beads were employed in a mixed-batch reactor to determine the degradation efficiency after 12 h of enzyme treatment. The obtained data showed that the immobilized laccase degraded more than 90% of 2,4-DNP within 12 h treatment. The immobilization process improved the activity and sustainability of laccase for degradation of the pollutant. Temperatures more than 50°C reduced the enzyme activity to about 60%. However, pH and the mediator concentration could not affect the enzyme activity. The degradation kinetic was in accordance with a Michaelis–Menten equation with Vmax and Km obtained as 0.25–0.38 μmoles/min and 0.13–0.017 mM, respectively. The stability of the immobilized enzyme was maintained for more than 85% of its initial activity after 30 days. Based on the results, it can be concluded that high resistibility and reusability of immobilized laccase on CPC-silica beads make it considerable choice for wastewater treatment. Keywords: Degradation, Laccase, Immobilization, Nano-porous silica beads, 2,4-dinitrophenol
Introduction Nitrophenols, categorized as priority pollutants, are one of the main common components which release from industrial effluents and deteriorate the quality of water resources. There are six possible dinitrophenol (DNP) forms and 2,4-Dinitrophenol (2,4-DNP) is the most important toxic and refractory pollutant [1]. 2,4-DNP, a yellowish crystalline solid, has been used in manufacturing of pesticides, pharmaceuticals, production of dyes, explosive materials, and as an indicator for the detection of potassium and ammonium ions. Its entrance into the environment may occur from industrial wastewaters, accidental spills, or as an intermediate metabolite due to degradation of pesticides containing 2,4-DNP [2]. For instance, wastewater from a dye manufacturing plant contained 3.2 mg/L DNP. * Correspondence: [email protected] 2 Department of Environmental Health, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran 3 Center for Solid Waste Research (CSWR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran Full list of author informatio
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