Water Contaminants from Pharmaceuticals and Chemical Industries
Water Contaminants from Pharmaceuticals and Chemical Industries
Abstract
In industrial processes, the generation of waste waters is unavoidable sometimes. It is therefore important to develop process for decontaminating this water. The treatment of toxic effluent that contains pharmaceutical and industrial chemicals cannot be satisfactorily attained through the use of conventional processes. Advanced oxidation processes (AOP) have been very vital and successful in their application to degrade these toxic compounds found in water. The high generation of extremely powerful oxidizing agent like the hydroxyl radical forms the back bone of the AOPs. This method is capable of destroying organic compounds until their pint of mineralization. Recent years have seen the fast growth of electrochemical processes that are highly efficient and environmentally friendly. This paper will focus on the use of Fenton’s reagent combined with electrochemical reagents. At the end of the research, a conclusion should be made whether the Fenton’s process is more viable and effective in decontamination of waste products when all biological treatments are non effective. This study aims at showing that the Fenton’s reagent is appropriate in the disinfection of industrial waste chemicals and pharmaceuticals.
Introduction
There has been an increase on the level of contamination on our water bodies due to the intensified chemical industrial processes. An effective counter for the waste disposal is therefore very important. This need for safe disposal processes has led to the development of economically and environmentally desirable process for waste disposal. The aquatic life is at great danger of extinction if effluent is just disposed into water bodies without considerable waste management processes. Furthermore, direct effects may be felt by the population through drinking from such water bodies, feeding on the fish that has fed on the chemicals or even ingestion of plant that grow in areas of contamination which may have absorbed these chemicals. The ever growing stringent regulations to safe guard water resources due to environmental concerns has led to studies aimed at improving on the conditions of effluent that is discharged to such water bodies both land water bodies and underground waters. Research has been directed greatly on the improvement of the current water treatment technologies. This has led to development of conventional and economical processes that are effective in dealing with toxic pharmaceuticals and chemical waste from industries. In the bid to mitigate possible effects of adverse health, negative environmental impact, safety, and in compliance with state law, institutions have supported and funded studies that are aimed at developing process that are necessary for chemical decontamination with practicality and economical viability. Waste products from chemical industries and the pharmaceutical labs are by products of research and industrial production processes. This waste has been identified to be one of the most polluting by-products to water bodies and the environment at large. They pose a serious problem in their disposal because of these chemicals’ unique characteristics.
At minimum, it is important that the final destination for waste be at a storage, treatment and effective disposal facility (National Research Council, 1995). Chemical actions, for instance neutralization, reduction and precipitation are the typical chemical processes for the treatments of waste chemical to produce an environmentally benign waste product. During the last decade, there has been significant development and improvements in Advanced Oxidation Processes (AOPs). These processes are used in the destruction of toxic chemicals from industry and the biologically refractory organic pollutants.
Fenton inorganic reactions processes are well recognized and have been in use in various waste water treatment processes. Strong hydroxyl radical formation is attributed to the high efficiency of this technique through the oxidation of Fe2+ to Fe3+. Fe2+ to Fe3+ ions which are both coagulants, that give the Fenton process the possibility of having two functions; that is coagulation and oxidation, during the treatment process (Badawy & Ali, 2006). Radical hydroxyl ions have the property of high potential electrochemical oxidation. The generation of the hydroxyl free radicals is possible through the combination of several reactions, for instance, hydrogen peroxide/UV, ozone/UV, photo-Fenton, titanium oxidation/solar radiation/hydrogen peroxide, or Fenton oxidation. Through a stepwise process, the radical thus formed will react with organic compounds breaking them down progressively.
The Fenton’s reagent, among the AOPs, has been effective in the waste water treatment and pre-treatment processes. Hydrogen peroxide combines with ferrous salts in the Fenton’s process under acidic conditions. There is the generation of hydroxyl radical through this reaction. It is this hydroxyl generated that is highly responsible for the oxidation processes in the reactions.
Emerging Ground Water Contaminants
Sophisticated new technologies give scientist the ability to determine the availability, even the smallest, of certain chemicals in ground water. This has led to the revelation of the presence of personal care products, drugs and other day to day substances that we use. These substances are commonly known as emerging contaminants. Testing for these emerging contaminants is expensive and very rare.
Pharmaceuticals
It has been recognized that there is a growing presence of pharmaceuticals waste products for a long time now (Richardson and Bowron, 1985). Pharmaceuticals have ended up in the environment through disposal of unused products, human excretion and agricultural usage (Poynton and Vulpe, 2009). These pharmaceuticals are present in ground and surface water linked to waste discarding. These waste type include; human and veterinary antibiotics, prescription drugs e.g. salbutamol, iodinated X-ray contrast media and non description drugs e.g. paracetamol. Some other chemical substances that have been identified in substantial quantities include chemotherapy drags and tamiflu (Buerge et al., 2009).
The impact of pharmaceuticals on the environment is largely speculative. These contaminants largely come from substances that are from personal care of health drugs. There is a great rise in the use of pharmaceuticals and personal care products. These products find their way into the environment through personal use, hospitals and veterinary activities. Some drugs that we consume can easily be broken down by the body whilst others are not. These drugs are also likely to be hard to degrade easily once in the environment. The possibility of their breakdown is due to the chemical composition, therefore this are the drugs that will be very harmful once they are in contact with ground water.
Industrial Chemicals
There are quite a big number of industrial drugs that can find their way into the environment. Many well-established problems have originated from this including petroleum hydrocarbon, chlorinated solvent, petroleum hydrocarbons and plasticizers (Garret et. al., 1986). The emerging ground compounds in this case may include; 1,4- dioxane which is highly water soluble, benzotriazole and dioxins which results as a result of degradation of other micro pollutants. Current surface water issues give an indication of possible groundwater contamination in the future. Chemical waste pollutants that load to the surface water are spatially and temporarily variable although the uncertainties and risks surrounding this issue can be modeled as desired.
There are a variety of was that potential quality contaminants flush their way into the ground water. Of these, the most rampant is through sewage treatment plants, discharge from individual septic system, and agricultural land use run offs. An example is antibiotics that are a very common drug used both by humans, livestock and poultry. Antibiotics are commonly found in waste water from local sewer treatment plants. Personal products and drugs are used by many people all throughout the world, but there is little information regarding the existence of substances in our water systems. From previous reports, emerging contaminants have been said to prevail in low concentration which can be as small as a trillionth per part. Health concerns have been raised due to the presence of contaminants such as antibiotics and steroids. Fish that live in streams that have been contaminated by steroids have shown a great alteration of their hormones. Furthermore, concerns are raised over prolonged prevalence of antibiotics in water that could lead to the development of disease-resistant bacteria strains that could render the current existing drugs ineffective.
Research Hypothesis
It is hypothesized that the use of Fenton Reagents in electrochemical treatment of the emerging water contaminants from pharmaceuticals and chemical industry is a viable solution for the decontamination of these water. This research will seek to research and confirm that the environment can be safe from the continuing spread of contamination from industrial chemicals and pharmaceuticals.
Electrochemical processes are best in applications where conventional oxidation techniques partly become oxidized leading to the formation of products that are toxic; and could be even more toxic than the original waste. This insufficiency could be due to kinetic reasons or when the pollutants under degradation are refractory to chemical oxidation. The reason for the use of radicals from AOPs is that they can non-selectively destroy organometalic and organic waste to their complete mineralization leading to the production of water, inorganic ions and carbon dioxide. The reaction of the radicals is rapid as they react with organics mostly through hydroxylation.
One of the advantages of electrochemical processes is that they are clean therefore environmentally friendly. They are also an effective procedure for the production of hydroxyl through indirect production using the Fenton’s reagent method (electro-Fenton). In this process, there is a coupling between the Fenton’s reagent and the electrochemistry. H2O2 are electro generated at the cathode which then reacts with the Fe2+ that is present in the aqueous medium which leads to the generation of the hydroxyl radicals, which is from the Fenton’s reaction (Garcia, 2011).
H2O2+ →OHads + •H + H+ + e_ ----------------------------eqn. 1
Fe2+ + H2O2 → Fe3+ + •OH + OH- --------------------------eqn. 2
As seen in eqn. 2, the outstanding oxidizing ability of electro-Fenton process is shown as the hydroxyl reacts rapidly in the medium. For reaction represented by eqn. 1, additional regeneration of Fe2+ from reduction of Fe3+ at the cathode enhances the reaction. Chemical oxygen demand (COD) is used as the determinant of the mineralization rate of the electrolyzed solution. In identification of chemical make up of treated solution, high performance liquid chromatography is added. Gas chromatography-spectrometry is to be used to identify reaction intermediates. The regeneration of Fe2+ may also be done by the oxidation of organic compounds with H2 O2 or the through the reaction of hydroperoxyl radical as illustrated below.
Fe3+ + R•→ Fe2+ + R+
Fe 3++ H2 O2 ↔ [Fe – OH]2+ + H+ ↔Fe2+ + HO2 • + H+
Fe3+ + HO2 •→ Fe2+ + H+ + O2
Experimental
The aim of the present thesis is to determine the efficiency of the Fenton electrochemical treatment on emerging water contaminants that are generated from chemical industries and pharmaceuticals. Pharmaceuticals waste and industrial waste chemicals from different companies will be used as the test sample. Analytical compounds, reagent grade or HPLC sampled from different companies are to be used in implementation of the experimental experiment with no further purification performed. Millipore Milli-Q system will provide ultra-pure water for the experiment with resistivity greater than 18MΏ cm at standard temperature and pressure.
Method
The conductivity, total dissolved solids and the pH of the waste sample is measured with the use of a calibrated M/s Elico meters. FTIR analysis is then conducted on the sample using the Nexus 670 tool that was considered between the range of 400 and 4000cm-1. KBr is used to make the sample as disc. Standard method, that is closed reflux method, was used to measure chemical oxygen demand.
The chemical cells are made up of a 1.5 liter glass reactor which is under the batch process. Predetermined amounts of oxidants are injected into the agitated reaction, for instance H2O2 and catalyst Fe2 .The experiment was done using a sample of one liter. The iron salt is added into the sample solution before the addition of hydrogen peroxide solution. A DC power supply is then connected to the electrodes. A magnetic stirred is then used to stir the sample at a constant speed of 185 revolutions per minute. The reaction is done at constant room temperature and pressure. The electrolyses process duration is assigned six hours. COD was estimated from drawing samples at regular intervals to estimate reduction efficiency of COD. The process is repeated three times. The current density was constant at 5A dm-2 was applied in the experiment.
The Fenton’s reagent is added to the solution which was done by adding 2 ml after every one hour in order to enhance the reactivity of the process. Analysis was done at intervals from withdrawn sample to determine the COD.
Results
In comparison to anodic oxidation, electro-Fenton method has a higher oxidation capability. Electro-Fenton is an indirect electro-oxidation method. This process depends on a continuous supply of aqueous acidic solution which is contaminated for the electrochemical process to proceed. Hydrogen peroxide is formed from the two-electron reduction of oxygen gas at cathodes.
O2(g) + 2H+ + 2e_ → H2O2--------------------------eqn. 4
Addition of a little amount of Fe2+ and Fe3+ ions is necessary to make the solution increase its solution power. This solubility power considerably increases the amount of electro generated H2O2. The catalytic nature of Fe2+ and Fe3+ is an advantage of the electro-Fenton reaction process. Hydroxyl radicals are produced from the oxidation of Fe3+ , while the Fe3+ initially added, or obtained from the oxidation process is continuously under reduction to form Fe2+ from reaction i.e. electrochemical catalysis, eqn. 4;
Fe3+ +e_ → Fe2+ ------------------------eqn. 5
The reactions 3 and 4 occur at the two-electrode undivided cell. The aqueous solution is maintained saturated with oxygen by bubbling compressed air through it. A combined action of •OH from the homogenous solution from Fenton reaction and that produced from the anode oxidizes the organic compounds. There is very small temperature changes expected throughout the experiment (Garcia, 2011).
Discussion
The active pH of the sample waste is a very important operational factor which is credited on the influence it has on the performance of electrochemical processes. The pH was therefore adjusted to 3.3 which is the known value that is suitable for the Fenton’s reagent treatment. In determining the efficiency of the process, it is necessary to calculate the energy consumed in the system. Energy consumption is expressed in kWh/kg of COD removed and is shown in equation given below.
Consumption of energy = IVTvol(COD change)
It is also important to determine the efficiency of the current that is used in the electrochemical processes. This process should be economically viable in its performance. Using COD values, the current efficiency is calculated as shown below
Efficiency of current = COD F vol8It
Where F is the Faraday’s constant, t is time in seconds, and finally the value 8 is the weight of oxygen.
Energy costs of the system is also to be determined which is given in kWh m_3 using the following equation.
Cost of energy = (VItvol )CODinchange in COD
V denotes voltage, I for applied current, vol. is solution volume, and t is for electrolysis time in hours.
Influences of temperature in the removal of COD are minimal and negligible. Temperature is therefore not a factor for consideration in carrying out this experiment.
Summary
The high ability of the electro-Fenton process to efficiently destroy organic micro pollutants makes it attractive. Usually, Pt anode is used although there are other anode materials that can be used for instance PBO2, BDD or iron. The production of hydroxyl radical by the reaction that occurs at the carbon felt cathode is electro generated through the use of Fe3+, Fe2+ and Cu2+.
In conclusion, electro-Fenton can be said to an ecological technique since it can lead to the production of POPs without the formation of dangerous wastes or the further addition of toxic chemical reagents. Furthermore, this process consumes a low energy in its operations therefore it is considered cost effective and reliable.
There have been several researches done on the viability of the use of Fenton’s reagent for decontamination of waste water. However, high investment costs have been identified as the greatest disadvantage for the AOPs and also cost in terms of high consumption in terms of energy and reagent and the plant structure complexity. Therefore, it can be concluded that the Fenton’s process is more viable and effective in decontamination of waste products when all biological treatments are non effective. This study aims at showing that the Fenton’s reagent is appropriate in the disinfection of industrial waste chemicals and pharmaceuticals.
Acknowledgements
I am grateful for the support that I received from my lecturers and academic colleagues from the day I started working on this research. I also express my heartfelt gratitude to the lab technicians who have been supportive all through.
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