Researcher: U. Valentine;
Mentor: B. Petrusevski, PhD;
Promotor: Prof. G. Amy, PhD
In general groundwater is preferred as a source of drinking water because of its convenient availability and its constant and good quality. However this source is vulnerable to contamination by several substances. Substances that can pollute groundwater are divided into substances that occur naturally and substances produced or introduced by human activities. Naturally-occurring substances causing pollution of groundwater include for example, iron, manganese, ammonium, fluoride, methane arsenic, and radionuclides. Substances resulting from human activities include, for example, nitrates, pesticides, synthetic organic chemicals and hydrocarbons, heavy metals etc.
Acceptable quality limits relative to micropollutant contents in drinking water are becoming increasingly lower and efficient elimination treatment processes are being implemented in order to meet these requirements. Metals contaminants at low concentration are difficult to remove from water. Chemical precipitation and other methods become inefficient when contaminants are present in trace concentrations. The process of adsorption is one of the few alternatives available for such situations.
Recent studies have shown that sands and other filter media coated with iron, aluminium, or manganese oxide, hydroxide or oxihydroxide were very good, inexpensive adsorbents which, in some cases, are more effective than the methods usually employed, such as precipitation-coprecipitation or adsorption on activated carbon grains. Selective adsorption can also retain elements that conventional treatments are unable to eliminate.
This phenomenon was demonstrated after having observed that iron and manganese in particular were more effectively eliminated using old filters than filters containing new sand and can be explained, in most cases, by a catalytic action of the oxide deposits on the surface of the sand grains.
The goal of this study is to improve the methods of adsorptive removal of selected metals present as cations or oxyanions (eg. iron, manganese, arsenic, lead and chromium) from groundwater by using different iron (hydro) oxides based media (iron oxide coated sand (IOCS), granular ferric hydroxide (GFH)).
Further more the study will give a better understanding on the interaction of a solute with a surface to be characterized in terms of the fundamental physical and chemical properties of the groundwater, the sorbent (iron oxide) and the adsorbate (the metal to be removed). The effects of pH, temperature, ionic strength, natural organic matter and other interfering ions (e.g. PO43-, Ca2+, SO42-, silica) on the adsorption will also be considered. The optimisation of regeneration capability and the leachability of adsorbed metals present in exhausted adsorbent will be determined.