EFFICIENT TREATMENT AND CONTROL OF CONCENTRATED PARTICULATE WASTE STREAMS
Advancing the chemical engineering fundamentals
Particulate Systems (T2-3P)
Keywords: ζ potential, isoelectric point (iep), titanium dioxide and shear yield stress
A result of many industrial manufacturing, minerals extraction and water treatment processes is the production of particulate waste materials. Many of these waste streams consist of oxide particulates in aqueous dispersion; treatment and disposal of these wastes will require the application of a variety of unit operations such as filtration devices and thickeners. Typically, these processes must operate across a wide range of conditions, such as variable pH and electrolyte concentrations, and knowledge of how these dispersions behave over such a range of conditions is therefore essential for the efficient design and control of waste processing systems. Classically, engineering design has concentrated on the hardware and its optimisation; here, we consider the detailed character of the dispersion and how this may be controlled and influenced to provide optimum operational conditions for existing unit operations.
A key control parameter for aqueous dispersions of mineral oxides is the zeta potential. In this work, we are investigating impact of mixed electrolyte systems, for example NaCl and Na2SO4, on the stability of titania dispersions. The electroacoustic zeta potentials and shear yield stresses for concentrated dispersions have been measured across a range of pH conditions and electrolyte concentrations (0.001 M – 1.0 M). This paper summarizes the results from these studies showing how the yield stress of concentrated aqueous suspensions for titanium dioxide, can be controlled through regulation of pH and the addition of background electrolytes (salt). The yield stress as a function of pH for titanium dioxide in mixed electrolytes showed a correlation in the shift in the position of the iep for the ζ potential results. When a change is made to the background electrolyte concentration or type there is a shift in the position of the iep. An increase in the electrolyte concentration leads to a shift in the iep towards the alkaline pH region. The consequences of these data for the efficient treatment of solid-liquid systems will be discussed.
Presented Monday 17, 13:30 to 15:00, in session Particulate Systems (T2-3P).
