Elsevier

Journal of Molecular Liquids

Volume 225, January 2017, Pages 544-553
Journal of Molecular Liquids

Optimization of electrocoagulation process for efficient removal of ciprofloxacin antibiotic using iron electrode; kinetic and isotherm studies of adsorption

https://doi.org/10.1016/j.molliq.2016.11.093Get rights and content

Highlights

  • Removal efficiency of CIP from hospital wastewater conducted using iron electrodes.

  • The process was able to remove > 99% of CIP in optimal condition.

  • Langmuir isotherm and second order kinetic model fitted well to experimental data.

Abstract

The present study focused on the removal of ciprofloxacin from hospital wastewater using electrocoagulation (EC) process by iron electrode and the kinetic and isotherms of adsorption were investigated. Response surface methodology (RSM) was used to evaluate the main effects of parameters, their simultaneous interactions and quadratic effect to achieve the optimum condition for EC process. The maximum removal rate was achieved at the current density of 15 mA·cm 2, initial CIP concentration of 60 mg·L 1, pH 7.5, inter-electrode distance 1.58 cm and electrolyte dose of 0.07 M NaCl within the equilibrium time of 20 min. The obtained experimental results are in good accordance with the Langmuir isotherm model for CIP adsorption on iron hydroxide by predicting the maximum adsorption capacity of 476.19 mg·g 1. The predicted model for treatment of synthetic wastewater is in satisfactory agreement with real hospital wastewater treatment. First and second order kinetic models were studied to figure out the exact mechanism of the CIP removal using EC process. The obtained results revealed that the second order kinetic model best fitted the experimental results and suggested that the chemisorption mechanism controlled the adsorption of CIP. Under the optimal conditions of EC process, electrode consumption (ELC) and electrical energy consumption (EEC) were found to be 0.0625 g during a single run and 0.522 kWh·m 3, respectively.

Graphical abstract

Major pathways of antibiotics release into the water resources and its cycle in aqueous ecosystems.

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Introduction

The rapid progress and development of the pharmaceutical industries in recent decades results in antibiotics pollution which is becoming severe contaminants of surface water and groundwater owing to their continuous input and persistence in aquatic ecosystems even at low concentrations. The release of antibiotics in natural ecosystems leads to increasing amount of antibiotic-resistant bacteria in aqueous environment [1]. One of the largest groups of antibiotics which have strong chemical stability and consequently are not fully metabolized in the body is fluoroquinolones (FQs). FQs are excreted in urine and animal excrement and eventually discharged into wastewater treatment plants (WWTPs). FQs revealed toxic effects on microbial activity thus they are often poorly biodegradable in biological treatment systems.

Ciprofloxacin (CIP) as the second generation of fluoroquinolones (FQs) is a synthetic antibiotic and has been widely used for the treatment of bacterial infectious disease in humans and animals. The lake of appropriate treatment systems in conventional wastewater treatment plant of drug manufacturers and hospitals and on the other hand unsuitable disposal of unused or expired CIP and incomplete metabolization of it in humans severely result in increasing the CIP contamination of surface water in the last decade [2] (Fig. 1).

It is reported that the presence of CIP in daily drinking water may cause nervousness, nausea, vomiting, headaches, diarrhea and tremors. Higher concentrations may cause serious adverse effects including thrombocytopenia, acute renal failure, elevation of liver enzymes, eosinophilia and leucopenia. On the other hand, the presence of antibiotics in water sources result in the development of bacteria resistant [3], [4], [5], [6]. Since the long term exposure to antibiotic cause chronic effects on human, organisms as well as ecological systems, the effective removal of them from water sources has become an increasingly important subject.

Literature surveys revealed that many research groups focused on developing an efficient and economical procedure for CIP contamination removal from drinking water supply and wastewaters before releasing them into the environment. Since CIP is resistant to microbial metabolism, it cannot be efficiently degraded by means of biological treatment processes [7]. Several studies including advanced oxidation process such as UV/H2O2 [8], O3 [9], photo catalyst degradable [10], have been developed for the removal of CIP contamination from aquatic solution.

However, among all of them electrochemical techniques such as electrocoagulation (EC) received extensive practical applicability by providing satisfactory result for the treatment of different wastewaters [11]. Its supplementary equipment is relatively cheaper compared to the other mentioned techniques. Moreover, the absence of harmful substances generation, producing low amount of TDS and secondary pollutants and removing the smallest size of colloidal particles are the other considerable advantages that caused increasingly usage of EC technique recently. EC as an alternative method has been suggested for chemical coagulation since it is environmental friendly and cheap to operate. Moreover, EC as an electrochemical method was developed to overcome the drawbacks of conventional water and wastewater treatment technologies and has been advocated as a novel approach in removing suspended solids and color substances from wastewaters. EC process provides a simple, reliable and cost-effective method for the treatment of wastewater without any need for additional chemicals, and thus the secondary pollution. The EC process is applied when removal of pollutant by chemical coagulation becomes difficult or impossible. It also reduces the amount of sludge, which needs to be disposed [12], [13], [14], [15], [16]. Since freshly metal hydroxide were prepared by EC process, the formed Fe flocs consist of polymeric Fe polymers with a long lasting positive charge increased the removal efficiency of pollutant through adsorption and precipitation. On the other hand, it forms less sludge which is readily settleable and easy to dewater as it is primarily composed of metallic oxides and hydroxides. Flocs formed by EC are similar to chemical flocs except that EC flocs are larger, contain less bound water and are more stable. Hence, they can be separated faster by settling and filtration [17], [18].

EC process involves three consecutive phases including generation of coagulants species in situ by electrolytic oxidation of the sacrificial metal anode (aluminum or ferric), inconstancy of the contaminants, suspension of the particulate and breaking of the emulsions and finally aggregation of the destabilized phases to form flocs [19], [20], [21], [22]. EC process provides a reliable method that has been successfully employed for the treatment of various industrial effluents such as plug board wastewater [23], poultry slaughterhouse [24], herbal pesticides [25], persistent organic compounds [26], etc. Besides the current studies in the field of electrochemistry, using an electrochemical sensor as a device which provides a certain type of response that is directly related to the quantity of a specific chemical species showed a rapid growing scientific field in environmental monitoring researches [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37].

In the present study a novel procedure for CIP contamination removal from hospital and industrial wastewater developed using EC technique. Since, most of the reported studies are based on one factor at the time method, in the current study, RSM was used to evaluate the main effects of parameters, their simultaneous interactions and quadratic effect to achieve the optimum condition for EC process. The effects of various operating parameters such as electrolyte type and concentration, initial CIP concentration, pH, current density, reaction time and inter-electrode distance were investigated to achieve the best efficient and economical CIP contamination remove condition. Moreover, first and second order kinetic models were studied to figure out the exact mechanism of the CIP removal using EC process. The obtained results revealed that the second order kinetic model best fitted the experimental results and suggested that the chemisorption mechanism controlled the adsorption of CIP. Consequently, the contaminants adsorption on the surface of generated absorbent were investigated using two common adsorption isotherms namely Freundlich and Langmuir models. The predicted model for treatment of synthetic wastewater is in satisfactory agreement with real hospital wastewater treatment.

Section snippets

Chemicals

CIP (C17H18FN3O3·HCl·H2O, 385.8 mol·wt.) purchased from Darou Pakhsh Pharmaceutical Company, Mashhad, Iran. Acetonitrile HPLC grade and analytical grade HCl were used to prepare the mobile phase. Other chemicals such as KCl, NaCl, KNO3, Na2SO4, CaCl2, NaOH, HOAc and ethanol were obtained from company Merck. All the solutions were prepared with chemicals of at least analytical grade using De-ionized water.

Electrocoagulation procedure

The electrocoagulation setup consisted of two iron plate electrodes with immersed dimensions

Electrolyte type and concentration

Preliminary studies were carried out in order to evaluate the effect of electrolyte type and concentration on the removal of CIP using Fe electrodes. The electrical energy consumption (EEC) was investigated using different type of electrolyte and showed in Fig. 2. The obtained results revealed that the minimum EEC was achieved in the presence of NaCl as electrolyte.

It is known that the addition of proper electrolyte to the EC cell demonstrates a significant improve in the efficiency of the

Conclusions

In the current study, the removal of CIP was investigated using electrocoagulation process as a green technology. Experimental design was carried out based on CCD with response surface methodology. RSM was used to evaluate the effects of process variables and their interactions to achieve their optimum condition. Under optimal operating condition including the amount of pH 7.5, inter-electrode distance of 1.5 cm, reaction time of 20 min, current density of 15 mA·cm 2 and electrolyte dose of 0.07 M

Acknowledgements

The authors express their appreciation to Kerman University of Medical Sciences, Kerman, Iran for cooperation in the current work.

References (57)

  • R. Kamaraj et al.

    An in situ electrosynthesis of metal hydroxides and their application for adsorption of 4-chloro-2-methylphenoxyacetic acid (MCPA) from aqueous solution

    J. Environ. Chem. Eng.

    (2014)
  • V. Khandegar et al.

    Electrocoagulation for the treatment of textile industry effluent–a review

    J. Environ. Manag.

    (2013)
  • M. Kobya et al.

    Treatment of poultry slaughterhouse wastewaters by electrocoagulation

    J. Hazard. Mater.

    (2006)
  • S. Ahmadzadeh et al.

    Highly selective detection of titanium (III) in industrial waste water samples using meso-octamethylcalix [4] pyrrole-doped PVC membrane ion-selective electrode

    Electrochim. Acta

    (2015)
  • A. Pardakhty et al.

    Highly sensitive and efficient voltammetric determination of ascorbic acid in food and pharmaceutical samples from aqueous solutions based on nanostructure carbon paste electrode as a sensor

    J. Mol. Liq.

    (2016)
  • H. Soltani et al.

    Determination of hydroquinone in food and pharmaceutical samples using a voltammetric based sensor employing NiO nanoparticle and ionic liquids

    J. Mol. Liq.

    (2016)
  • M. Fouladgar et al.

    Application of a nanostructured sensor based on NiO nanoparticles modified carbon paste electrode for determination of methyldopa in the presence of folic acid

    Appl. Surf. Sci.

    (2016)
  • V.K. Gupta et al.

    NiO/CNTs nanocomposite modified ionic liquid carbon paste electrode as a voltammetric sensor for determination of quercetin

    Int. J. Electrochem. Sci.

    (2015)
  • M. Yoosefian et al.

    Solvents effect on the stability and reactivity of tamoxifen and its nano metabolites as the breast anticancer drug

    J. Mol. Liq.

    (2016)
  • S. Vasudevan et al.

    Studies on the Al–Zn–In-alloy as anode material for the removal of chromium from drinking water in electrocoagulation process

    Desalination

    (2011)
  • S. Ahmadzadeh et al.

    A conductometric study of complexation reaction between meso-octamethylcalix [4] pyrrole with titanium cation in acetonitrile-ethanol binary mixtures

    Int. J. Electrochem. Sci.

    (2011)
  • S. Ahmadzadeh et al.

    Conductometric measurements of complexation study between 4-isopropylcalix [4] arene and Cr3 + cation in THF-DMSO binary solvents

    Measurement

    (2015)
  • M. Rezayi et al.

    Thermodynamic studies of complex formation between Co (Salen) ionophore with chromate (II) ions in AN-H2O binary solutions by the conductometric method

    Int. J. Electrochem. Sci.

    (2011)
  • M. Rezayi et al.

    Conductometric determination of formation constants of tris (2-pyridyl) methylamine and titanium (III) in water-acetonitryl mixture

    Int. J. Electrochem. Sci.

    (2011)
  • M. Yoosefian et al.

    A theoretical study on the structure of 2-amino-1, 3, 4-thiadiazole and its 5-substituted derivatives in the gas phase, water, THF and DMSO solutions

    J. Mol. Liq.

    (2015)
  • M. Yoosefian et al.

    Density functional theory (DFT) study of a new novel bionanosensor hybrid; tryptophan/Pd doped single walled carbon nanotube

    Phys. E Low Dimens. Syst. Nanostruct.

    (2016)
  • M. Aghazadeh et al.

    Determination of antimicrobial resistance profile and inducible clindamycin resistance of coagulase negative staphylococci in pediatric patients: the first report from Iran

    World J. Pediatr.

    (2015)
  • Y. Fasihi et al.

    Molecular detection of macrolide-and lincosamide-resistance genes in clinical methicillin-resistant Staphylococcus aureus isolates from Kerman, Iran

    Arch. Pediatr. Infect. Dis.

    (2016)
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