Modification of ASTM-D2492 standard test method for determining sulfur forms in environmental monitoring of porphyry copper waste dump, Case Study: Sarcheshmeh Copper Mine

In environmental impact assessment of acid mine drainage، the content determination of pyrite content and hydroxy-sulfate minerals is essential. The ASTM-D2492 standard test is an experimental method for precisely determination of pyrite and hydroxy-sulfates minerals in coal wastes. Due to mineralogical differences between coal and porphyry copper wastes، this test has to be modified for porphyry copper wastes. The main cause of error in this experiment for copper wastes is the lack of balance between acid and weight of sample in the test، thus it seems that the weight of samples have to be determined. In this study، 15 subsamples have been derived from three samples of copper waste، weighted in five levels as 1، 0. 4، 0. 3، 0. 2، and 0. 1 g. These subsamples have been tested with ASTM-D2492 standard test method and the results compared to quantitative XRD. Based on the results، the sulfur content related to hydroxysulfate minerals was independent from weight of sample and the sulfur in pyritic form was equal with quantitative XRD results in the weight of 0. 2 g. In addition، by using ASTM-2492 data، the method presented by Romero et al has been modified which became capable to indicate the environmental risk and bioavailability of toxic elements. This method was on the basis of statistical correlation analysis between ASTM-D2492 and ICP data and results in identification of toxic elements founded in hydroxysulfate minerals and adsorbed on iron hydroxides. To verify the method، 60 samples were taken from Nos. 19’s and 31’s Sarcheshmeh waste dumps and analyzed by ASTM-D2492 and ICP methods. It was found that Cd، Co، Cr، Cu، Mn and Ni were incorporated into the hydroxysulfate minerals and As، Cr and Mo were adsorbed on iron hydroxides. These results were consistent with previous studies conducted in the Sarcheshmeh copper mine using sequential extraction experiments.