In this research, we studied the use of microwave pretreatment to enhance the efficiency of Au leaching from gold concentrate. The gold concentrate was pretreated using microwaves with different irradiation time. The sample temperature was increased up to 950 °C by the microwave irradiation. A scanning electron microscope-energy dispersive spectrometer showed the evolution of microcracks and the reduction of sulfur on the mineral surface. X-ray diffraction data also showed the mineral phase shift from pyrite to hematite or pyrrhotite. A leaching test was conducted for the microwave-treated and untreated gold concentrates using thiourea. Although the thiourea leaching recovered 80% of Au from the untreated concentrate, from the treated concentration, the Au could be recovered completely. Au leaching efficiency increased as the microwave irradiation time increased, as well as with a higher composition of thiourea.

A simple method is proposed for the determination of the deposition coefficient, which plays an important role in bacterial transport in a porous media. The method relies on the analytical solution of an advection-dispersion-deposition equation for the step input of a bacterial solution. The step input solution can be simplified when time goes to infinity, and thereby the deposition coefficient can be obtained as a function of the maximum concentration and peclet number. The deposition coefficient given by the simple method yields a similar expression to those of previous studies with a slight modification. Comparison of the simple method with other methods revealed that it offers an advantange of a wider application, even to a square pulse input as well as step input of a bacterial solution, and that calculation of bacterial mass fraction is not required. Theoretical validation revealed that the method can be valid for the conditions of pulse duration greater than 0.8 pore volume in the column study with Pe 300–400.