Phosphate adsorption onto laterite and laterite waste from a leaching process

Abstract

It has been proved by several authors that adsorption is a good way to remove phosphate from wastewaters, especially using fly ash or modified fly ash as an adsorbent. There are also various studies regarding removal of arsenic and mercury with an adsorbent called laterite, which is a type of soil rich in iron and aluminium, usually formed in hot and wet tropical areas. The main aim of this research is to study the removal capacity of laterite and modified laterite toward phosphate. Different kinds of laterite have been provided by Kinney Environmental Science Services Consultancy, a local company based in Northern Ireland. Properties of laterite have been determined using X-ray diffractograms. One of the innovations presented in this thesis is the calibration of phosphorus with a colorimetric method. It was carried out in order to avoid the use of much more expensive methods, such as the Inductively Coupled Plasma spectrometry (ICP). Subsequent adsorption experiments include: adsorption kinetics, pH studies, adsorption isotherms, temperature studies, thermodynamic parameters and column studies. Laterite charred at different temperatures has been used and different particle sizes have also been tested. Finally, a global comparison of the results with other authors has been made, as well as with some other synthesized materials that could be used for future research.