The Catalytic Removal Of Bisphenol A And Chlorpyrifos Based On The Immobilized Hemoglobin Combined With Electrochemical Technology

Environmental hormones, called environmental endocrine disruption chemicals (EDCs), are comprised of an extensive and expanding spectrum of compounds which can go into food chain through the surrounding, and are accumulated in the animals and human bodies. They also can interfere with animals and human endocrine systems and damage the reproductive system of animals and human seriously. Most of them were discharged into the environment with the production and the life of the humanity. Bisphenol A (BPA) and chlopyrifos are the typical forms. Due to a widely use of these plastic products and pesticides in recent years, the damages caused by BPA and chlopyrifos increased increasingly. It is high time to develop a variety of treatment techniques for the decomposition, detoxification and removal of bisphenol A and chlopyrifos in water. Hemoglobin (Hb) is known to have some intrinsic peroxidase activity owing to its close structural similarity to peroxidase, and these characteristics make it possible to catalyze the removal of pollutants. This paper contains three main parts:(1) The electrochemical reactor was arranged with a stainless steel and an enzymatic film as anode and cathode, respectively. The enzymatic film was formed by immobilizing hemoglobin on carbon fiber. In the membraneless electrochemical reactor, hydrogen peroxide was generated in situ in cathode and bisphenol A was oxidated and removed by the combining hemoglobin with hydrogen peroxide. The experimental conditions for electrogeneration of hydrogen peroxide and electroremoval of bisphenol A were optimized. Experimental results showed that in supplied voltage 2.4 V, pH 5.0 and oxygen flow rate 25 mL/min, the electrogeneration of hydrogen peroxide and the electroenzymatic removal of bisphenol A were highest. Under optimal operation conditions, the removal efficiency of bisphenol A reached 50.7 % in 120 min and then kept constant when further prolonging the period of reaction. Compare with electrochemical and biochemical methods, the removal of BPA through electroenzymatic method was comparatively favorable. (2) Catalytic removal of bisphenol A from aqueous solution with hemoglobin immobilized on amino-modified magnetic nanoparticles as an enzyme catalyst was reported. The amino-modified magnetite nanoparticles were firstly prepared by the coprecipitation of Fe²⁺ and Fe³⁺ with nh₃·H₂O and then modified by 3-aminopropyltriethoxysilane. The immobilization process was optimized by examining enzyme concentration, glutaraldehyde concentration, crosslink time, and immobilization time. The optimum conditions for the removal of bisphenol A with immobilized hemoglobin were also investigated. The immobilized hemoglobin showed the same or even higher activity in wider ranges of temperature and pH than that of its free form. After being immobilized on the support, the hemoglobin exhibited good thermo stability and storage stability. Under the optimality conditions, the removal efficiency of bisphenol A was about 80.3 %. The immobilization had a beneficial effect on the stability of hemoglobin and conversions of bisphenol A. According to the proposed breakdown pathway and the intermediates, the enzyme-catalytic removal of bisphenol A by the immobilized hemoglobin is considered to be an effective method.(3) The degradation of chlorpyrifos by the combination of immobilized hemoglobin and in situ generated hydrogen peroxide is reported for the first time. We have immobilized hemoglobin on graphite felts to catalyze the removal of chlorpyrifos in an electrochemical-enzyme system and found that more than 98 % chlorpyrifos is degraded under the optimal condition determined by parametric experiments. Furthermore, the degradation products of chlorpyrifos are also studied and identified through liquid chromatography-mass spectrometry analysis. These results suggested a possible degradation mechanism of chlorpyrifos with low-power and high-efficiency, revealed the feasibility for hemoglobin as a substitute for some expensive natural enzymes, and demonstrated the application prospect of the electroenzymatic process in the treatment of organophosphorus compounds in wastewater.