Degradation of 2-Chlokophenol in Water Using Advanced Oxidation Processes

The presence of endocrine disruptor chemicals (EDCs) in treated wastewater lately, is alarming. Chlorophenols, an endocrine disruptor chemical compound is hardly eliminated in water using conventional treatment. In this study, contaminated water containing 2-Chlorophenol was treated using the Advanced Oxidation Processes (AOPs) reactor (anolyte solution/ozone/UV) and anolyte solution alone. Various conditions such as initial pH values, ozone dosages, reaction time and initial 2- Chlorophenol concentrations were tested to achieve the optimum degradation of 2- Chlorophenol. Possible intermediates and by-products in each treatment effluents were investigated. Results showed that almost 90% of 2-Chlorophenol (5mgIL) degraded in water with initial alkaline pH values (11-12) using AOPs reactor (anolyte solution (O.4L)/Ozone 50% (0.5 1 mg/L)/UV). Complete (1 00%) degradation of 2-Chlorophenol in \i.ater was achieved when initial concentration of 2-Chlorophenol was 0.04 mg/L in neutral pH condition. On the other hand, at least 70% of the ZChlorophenol degraded when treated with anolyte solution in all initial pH values and initial 2-Chlorophenol concentrations. Complete (100%) degradation of 2-Chlorophenol occurred when the initial concentration of 2-Chlorophenol was 1.0 mg/L in original pH condition. All effluent samples had acidic pH value except those 2-Chlorophenol solutions with initial alkaline pH values. Comparison between two treatments showed that anolyte solution was more effective to degrade 2-Chlorophenol than AOPs reactor at original and neutral pH conditions. The degradation of 2-Chlorophenol compounds in water was achieved up to 100% using anolyte solution compared to the AOPs reactor at higher 2- Chlorophenol concentration in most cases. The 2-Chlorophenol degraded intermediates and by-products using AOPs reactor and anolyte solution were mainly alkenes, alkanes, carboxylic acid, ketones and ether functional group compounds

Use of Desulfovibrio and Escherichia coli Pd-nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil

BACKGROUND Desulfovibrio spp. biofabricate metallic nanoparticles (e.g. ‘Bio-Pd’) which catalyse the reduction of Cr(VI) to Cr(III) and dehalogenate polychlorinated biphenyls (PCBs). Desulfovibrio spp. are anaerobic and produce H2S, a potent catalyst poison, whereas Escherichia coli can be pre-grown aerobically to high density, has well defined molecular tools, and also makes catalytically-active ‘Bio-Pd’. The first aim was to compare ‘Bio-Pd’ catalysts made by Desulfovibrio spp. and E. coli using suspended and immobilised catalysts. The second aim was to evaluate the potential for Bio-Pd-mediated dehalogenation of PCBs in used transformer oils, which preclude recovery and re-use.\ud RESULTS Catalysis via Bio-PdD. desulfuricans and Bio-PdE. coli was compared at a mass loading of Pd:biomass of 1:3 via reduction of Cr(VI) in aqueous solution (immobilised catalyst) and hydrogenolytic release of Cl- from PCBs and used transformer oil (catalyst suspensions). In both cases Bio-PdD. desulfuricans outperformed Bio-Pd E. coli by ~3.5-fold, attributable to a ~3.5-fold difference in their Pd-nanoparticle surface areas determined by magnetic measurements (Bio-PdD. desulfuricans) and by chemisorption analysis (Bio-PdE. coli). Small Pd particles were confirmed on D. desulfuricans and fewer, larger ones on E. coli via electron microscopy. Bio-PdD. desulfuricans-mediated chloride release from used transformer oil (5.6 $\pm$ 0.8 $\mu$g mL-1 ) was comparable to that observed using several PCB reference materials. \ud CONCLUSIONS At a loading of 1:3 Pd: biomass Bio-PdD. desulfuricans is 3.5-fold more active than Bio-PdE. coli, attributable to the relative catalyst surface areas reflected in the smaller nanoparticle sizes of the former. This study also shows the potential of Bio-PdD. desulfuricans to remediate used transformer oil

Performance of Italian zeolitic tuffs and pozzolana in 2-chlorophenol removal from contaminated groundwater. Lab-scale experience

The physical and chemical properties of zeolites and the availability of localized deposits of naturally occurring zeolitized tuffs and pozzolana, make them desirable for and applicable to the remediation of contaminated groundwater. This paper documents the results of a laboratory study to test the capacity of native Italian zeolites to remove 2-chlorophenol (2-CP) from water. Italian zeolitic tuff and pozzolana were characterized in terms of their chemical and structural properties and of their adsorption capacities. Moreover, the experimental activity investigated their adsorption behaviour: time and pH dependence of the adsorption process was evaluated. The results of the time-dependence adsorption study under a constantly stirred condition showed that the adsorption increases with a longer contact time for all samples; the highest adsorption occurred at pH=8 divided by 8.5. Due to the good removal efficiencies obtained, a column test simulating the condition of an in situ permeable reactive barrier was carried out, in order to estimate the removal kinetics and the long-term behaviour. The removal efficiencies reached values higher than 90%, even if some long-term performance worsening occurred, due to the progressive exhaustion of the adsorption sites. These experiments demonstrate the capacity of naturally occurring zeolites to remove 2-CP from water and the opportunity to make economic use of these native deposits for in situ groundwater remediation

Photocatalytic degradation of 2-chlorophenol by tio2: kinetic studies

Kinetic studies of 2-chlorophenol photocatalytic degradation are carried out in a batch stirred built in quartz laboratory scale, using TiO2 as catalyst photoactived with ultraviolet light. Experimental design is performed using as independent variables or factors: catalyst concentration, catalyst calcinations temperature and initial concentration of 2-chlorophenol, to establish the best conditions of the degradation process. The experimental data were fitted with the Langmuir-Hinshelwood model. A kinetic constant k of 0.24 mg L-1min-1 was obtained.Fil: Morales, Graciela del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Sham, Edgardo Ling. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Cornejo, Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Farfan Torres, M. E.. Universidad Nacional de Salta. Facultad de Ciencias Exactas; Argentin

The chemistry of ultrasonic degradation of organic compounds

The destruction of toxic organic molecules using advanced oxidation processes (AOPs) is a potent tool for pollution control and environmental protection. Ultrasound is a convenient and effective method of generating hydroxyl radicals which is the key oxidant in AOPs. This review describes the use of ultrasound and associated chemical reactions, with and without additives, as a powerful means of remediating water contaminated with organic pollutants. After a brief introduction to ultrasound and sonochemistry, their application for the oxidation of polycyclic aromatic hydrocarbons, phenol and substituted phenols is considered. Next is the decomposition of chlorinated phenols, and other chlorinated organics, then removal of recalcitrant smaller organic molecules. A discussion follows of recent work that has investigated the effects of initial concentration of substrates; the use of different ultrasonic frequencies; the inclusion of oxidising species, inorganic particles, or salts and their contribution to enhanced degradation. Finally, brief comments are made on the status of ultrasound as an AOP treatment

AD–OX: A sequential oxidative process for water treatment— Adsorption and batch CWAO regeneration of activated carbon

A sequential process for water treatment involving usual adsorption on activated carbon (AC) followed by wet air catalytic oxidation of the adsorbed pollutants has been carried out in a fixed bed reactor with a mixture of two model pollutants. The first step achieves water purification while the second one reduces the organic pollution but also, more importantly, performs some AC in situ regeneration. The experimental work has been done with AC yet extensively used and stabilized by long range continuous oxidation. The two steps have been analyzed successively showing very important drop of adsorption capacity with respect to fresh AC but efficient oxidative partial regeneration. As expected with used AC no more evolution occurs in between two consecutive runs. The first step of competitive adsorption has been simulated by a model leading to higher diffusivities than estimations based on correlations. The main features of the complex second step, involving simultaneous non-isothermal desorption and three phase catalytic reaction, are qualitatively explained

Metabolism of profenofos to 4-bromo-2-chlorophenol, a specific and sensitive exposure biomarker.

Profenofos is a direct acting phosphorothioate organophosphorus (OP) pesticide capable of inhibiting β-esterases such as acetylcholinesterase, butyrylcholinesterase, and carboxylesterase. Profenofos is known to be detoxified to the biologically inactive metabolite, 4-bromo-2-chlorophenol (BCP); however, limited data are available regarding the use of urinary BCP as an exposure biomarker in humans. A pilot study conducted in Egyptian agriculture workers, demonstrated that urinary BCP levels prior to application (3.3-30.0 μg/g creatinine) were elevated to 34.5-3,566 μg/g creatinine during the time workers were applying profenofos to cotton fields. Subsequently, the in vitro enzymatic formation of BCP was examined using pooled human liver microsomes and recombinant human cytochrome P-450s (CYPs) incubated with profenofos. Of the nine human CYPs studied, only CYPs 3A4, 2B6, and 2C19 were able to metabolize profenofos to BCP. Kinetic studies indicated that CYP 2C19 has the lowest Km, 0.516 μM followed by 2B6 (Km=1.02 μM) and 3A4 (Km=18.9μM). The Vmax for BCP formation was 47.9, 25.1, and 19.2 nmol/min/nmol CYP for CYP2B6, 2C19, and 3A4, respectively. Intrinsic clearance (Vmax/Km) values of 48.8, 46.9, and 1.02 ml/min/nmol CYP 2C19, 2B6, and 3A4, respectively, indicate that CYP2C19 and CYP2B6 are primarily responsible for the detoxification of profenofos. These findings support the use of urinary BCP as a biomarker of exposure to profenofos in humans and suggest polymorphisms in CYP 2C19 and CYP 2B6 as potential biomarkers of susceptibility

Novel biological approaches for the removal of chlorophenolics [AOX] from bleach plant effluent

No abstract available

Intensification of toxic chlorophenolic compounds degradation over efficient microwave-dried silica-doped tetragonal zirconia nanocatalysts

The work aims to evaluate the efficient microwave (MW) drying method of silica-doped tetragonal zirconia nanocatalysts (SZN-M) for intensification of the degradation of toxic chlorophenolic compounds. The catalyst dried under a conventional oven (SZN-O) was also conducted for comparison. The MW drying time was reduced six times and three times less energy was used than the conventional oven drying. The catalysts were characterized by Fourier-transform infrared, X-ray diffraction, electron spin resonance, nitrogen adsorption-desorption analyses, zeta potential, ultraviolet–visible diffuse reflectance spectroscopy and photoluminescence analyses. Compared with SZN-O, the SZN-M possessed a higher number of Si-O-Zr bonds that led to a greater amount of oxygen vacancies, metal defect sites, larger pore size as well as surface area, and hence displayed excellent performance toward the degradation of toxic 2-chlorophenol, 2-CP (92%), while only 67% for the former. The SZN-M achieved to reduce the total organic carbon and biological oxygen demand up to 88% and 89%, respectively, while for SZN-O, the reduction was up to 82% and 84%. The catalysts still remained active after five cycles and are highly capable of degrading various chlorophenolic compounds that could be very beneficial for the wastewater treatment

Sequentially alternating pollutant scenarios of phenolic compounds in a continuous aerobic granular sludge reactor performing simultaneous partial nitritation and o-cresol biodegradation

Industrial wastewater treatment plants must operate properly during the transient-state conditions often found in the industrial production. This study presents the performance of simultaneous partial nitritation and o-cresol biodegradation in a continuous aerobic granular reactor under sequentially alternating pollutant (SAP) scenarios. Three SAP scenarios were imposed during the operation of the granular reactor. In each one, a secondary recalcitrant compound (either p-nitrophenol (PNP), phenol or 2-chlorophenol (2CP)) were added for a short period of time to the regular influent containing only ammonium and o-cresol. Partial nitritation and o-cresol biodegradation were not inhibited by the presence of PNP or phenol and both compounds were fully biodegraded. On the contrary, the presence of 2CP strongly inhibited both processes within 2 days. However, the reactor was recovered in a few days. These findings demonstrate that treatment of complex industrial wastewaters with variable influent composition is feasible in a continuous aerobic granular reactor