Laboratory Remediation of Iron-Sulphate Contaminant in Acid Mine Waters Using Waste Rocks

In this paper, laboratory techniques of removing acid mine drainage rich in iron and sulphate is highlighted. AMD are contaminated water generated from mining of metals rich ore bodies such as pyrites and other iron and sulphide rich minerals. Three waste rocks of shale, bentonite and a mixture rock (shale-bentonite-calcrete) were used in removing the iron-sulphate concentration. Physico-chemical remediating process was carried out in the laboratory targeting the removal of the iron and sulphate in the AMD using these waste rocks. The remediation involved grinding the waste rocks into different particle sizes and sorting the grains using ASTM standard. The sorted waste rocks were arranged into three transparent bottle with regulated dip end. Each waste rock was placed into a distinct bottle. AMD rich in iron-sulphate was sourced from an abandoned mine. The iron-sulphate concentration in the AMD was determined using ICP-MS. The iron-sulphate concentration was determined before and after the remediation. Result show iron concentration in the AMD was 253 mg/l before remediation and 0.08 mg/l, 0.02 mg/l, 0.80 mg/l after remediation for bentonite, mixture and shale respectively. Likewise, sulphate concentration before remediation was 5067 mg/l before remediation and 3207 mg/l, 3662 mg/l, 2238 mg/l after remediation for bentonite, mixture and shale respectively. The laboratory experimentation has shown that controlled laboratory techniques can be used in removal of iron and minimise sulphate contained in AMD. The use of waste rocks of shale or bentonite with variety of grain size contents will remove iron-sulphate contamination and if use as liners in a constructed wetland will minimise the generation of AMD.