Recent years, pharmaceutical chemicals and personal care products are one of the recognized emerging pollutants due to the wide usage and discharge to the environment. Surface water, portable water and ground water containing the pharmaceutical waste concentration range from parts-per-trillion to parts-per-billion in the aquatic environment. Among various medicines, antibiotics have mostly detected in the environment because of an extensive usage. Antibiotics would raise the serious potential threats to human health and ecosystems. The following reason, the antibiotics can be causes for concern, extensively used (human and veterinary medicine), does not completely metabolized, antibiotic resistance and formed the accretion to these substances in environment and water resource.
Fluoroquinolone antibiotic was one of the most vital synthetic antibiotics as compared to other antibiotics, such as b-lactam, macrolides, tetracyclines and sulfonamides. It is amphoteric quinolones, fluoro group was attached to the central ring systems of these compounds. It has been used broad-spectrum of antibiotics in the action of bacterial infections diseases around the world. Huge amount of fluoroquinolone was sensed from the environment because it has poorly biodegradable and end of the water treatment effluent the parent form was released. The following side effect may be caused by a fluoroquinolone drug, common side effects are diarrhea, nausea, severe tendon damage, dermatologic, hepatic and nerve damage.
Amongst fluoroquinolone drugs norfloxcin (NRF) has second generation drug, numerously used against urinary tract infections, bladder infections, respiratory tract and gastrointestinal infections. However, NRF was difficult to metabolize and it can be ejected as parent active form to the environment. The massive usage and high amount of releasing of the NRF was highly toxic to the microorganism and it tainted to aquatic plants and organism, and it has produced serious endanger the ecosystem. This drug was not recommended for pregnant women because it created cartilage spoil in weight-bearing joining. So the NRF removal was more important process for the environment. Different method was implemented to remove NRF and reach to the goal. NRF was removed by biodegradation process at least three intermediates was formed as secondary waste.
In chemical oxidation process, hazardous degradation intermediate was formed as similar to biodegradation process. Photolysis, adsorption and ozonation process were employed to the remove of NRF, this method secondary pollutants were formed. Now recent years, advanced oxidation process (AOP) is more interesting process used to remove the micro-pollutants. The photocatalytic degradation technology has more environmental friendliness method, high energy utilization and low cost method. In pharmaceutical pollutants degradation, photocatalytic degradation process has been most excellent technique. Recently, semiconductor photocatalyst has widely used due to the low mass transfer and applicable ambient temperature and pressure. Nowadays, graphitic carbon nitride (g-C3N4) semiconductor catalysts have been exercised to degrade the pharmaceutical pollutants because active as visible light. g-C3N4 has higher nitrogen content polymeric metal free semiconductor. Reduction ability of photogenerated electron has so high because the conduction band (CB) of g-C3N4 was extremely negative value.
Although, g-C3N4 have low photocatalytic activity due to the quick recombination charge carriers and insufficient visible light absorption. To reduce the above problem, g-C3N4 was coupled other semiconductor to form heterojunction is an effective strategy. Transition metal tungstates have very promising photocatalyst material due to the impending application. Intrinsic p-type semiconductor with suitable band gap and high activity of NiWO4 composite make to form an appropriate photocatalyst for the treatment of pharmaceutical pollutants degradation. NiWO4 nanoplates can be coupled with the polymeric semiconductor g-C3N4 nanosheets, boost the photocatalytic activity under visible light.
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