William Wilson Anku

Phenolic Compounds in Water: Sources, Reactivity, Toxicity and Treatment Methods

Phenolic compounds exist in water bodies due to the discharge of polluted wastewater from industrial, agricultural and domestic activities into water bodies. They also occur as a result of natural phenomena. These compounds are known to be toxic and inflict both severe and long‐lasting effects on both humans and animals. They act as carcino‐ gens and cause damage to the red blood cells and the liver, even at low concentrations. Interaction of these compounds with microorganisms, inorganic and other organic com‐ pounds in water can produce substituted compounds or other moieties, which may be as toxic as the original phenolic compounds. This chapter dwells on the sources and reactivity of phenolic compounds in water, their toxic effects on humans, and methods of their removal from water. Specific emphasis is placed on the techniques of their removal from water with attention on both conventional and advanced methods. Among these methods are ozonation, adsorption, extraction, photocatalytic degradation, biological, electro‐Fenton, adsorption and ion exchange and membrane‐based separation.

Influence of ZnO concentration on the optical and photocatalytic properties of Ni-doped ZnS/ZnO nanocomposite

Photocatalysts consisting of nickel-doped ZnS/ZnO core shell nanocomposites with varying concentrations of ZnO was synthesized through chemical precipitation method. The catalyst was deployed in photocatalytic degradation of indigo carmine dye as a model organic pollutant. Characterization of the samples was achieved through the use of X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, UV–vis spectroscopy and energy dispersive spectroscopy. The composites consist of wurtzite ZnO phase deposited on cubic ZnS. Optical absorption, crystallite sizes and photocatalytic degradation efficiency increased with increasing ZnO concentration. Bandgap values of ZnS also decreased appreciably with increase in ZnO concentration. Ni-doped ZnS/(0.5 M ZnO) was identified as the most efficient catalyst with 91% dye degradation efficiency at a rate of 15.38 × 10−3 min−1 in 180 min. Meanwhile, the pristine ZnS degraded 25% of the dye at the rate of 1.53 × 10−3 min−1 within the same time. The Ni-doped Zns/(0.5 M ZnO) was used to degrade the dye on the basis of influence of factors such as solution temperature, hydrogen peroxide (H2O2) and ethanol contents. Dye degradation increased with increase in temperature, but decreased with ethanol content. H2O2 content initially caused enhanced dye degradation but the efficiency decreased with higher H2O2 content.

Photocatalytic Degradation of Pharmaceuticals Using Graphene Based Materials

Pharmaceutical products are produced purposely for the treatment of diseases with the aim of improving human health. Despite their usefulness to human and animal health, pharmaceuticals are now being regarded as emerging environmental pollutants. This is due to their increased use and the fact that they are indiscriminately discharged into the aquatic environment from hospitals, households, industries, pharmacies, as well as leakages and leachates from municipal wastewater treatment plants and landfill sites. Moreover, the conventional methods of wastewater treatment were not designed with these emerging pollutants in mind resulting in the discharge of untreated or incomplete treated wastewater into water bodies. Pharmaceuticals in water are believed to exert deleterious effects on humans and aquatic organisms. The concern to remove these pharmaceutical wastes and their metabolites from wastewater before their final discharge into water bodies has culminated in the development of a wide variety of other treatment technologies such as adsorption, chemical oxidation, liquid extraction, biodegradation, and so on. However, because these pharmaceuticals are mostly water soluble and non-biodegradable, most of the treatment techniques are inappropriate for their effective removal. The deployment of an appropriate technique for effective degradation of pharmaceutical wastes in water has therefore become a necessary requirement. This chapter therefore provides a detailed discussion on pharmaceuticals in general, their occurrence in water and their health consequences. It also delved into the photocatalytic degradation of these chemicals in water with emphasis on the use of graphene based materials.