Potential use of densified polymer-pastefill mixture as waste containment barrier materials.

Mining activities generate a large amount of solid waste, such as waste rock and tailings. The surface disposal of such waste can create several environmental and geotechnical problems. Public perception and strict government regulations with regards to the disposal of such waste compel the mining industry to develop new strategies which are environmentally sound and cost effective. In this scenario, recycling of such waste into mining or civil engineering construction materials have become a great challenge for the mining and civil engineering community. Hence, in this study, taking advantage of the inherent low hydraulic conductivity of paste tailings (pastefill), small amounts (0.05, 0.1, 0.2, 0.5%) of a super absorbent polymer (SAP) are added to the latter after moisturizing the tailings. The resulting densified polymer-pastefill (PP) materials are compacted and submitted to permeability tests at room temperature and performance tests under cyclic freeze-thaw and wet-dry conditions to evaluate their suitability as a barrier for waste containment facilities. Valuable results are obtained. It is found that the hydraulic conductivity of the proposed barrier material (PP) decreases as the amount of SAP increases. Hydraulic conductivity values as low as 1 × 10(-7) and 6 × 10(-9)cm/s are obtained for PPs which contain 0.1-0.5% SAP, respectively. The PP material also shows relatively good resistance to cyclic freeze-thaw and wet-dry stresses. The results show that negligible to acceptable changes in hydraulic conductivity occur after five freeze-thaw and six wet-dry cycles. None of the changes reach one order of magnitude. As a final step, a cost analysis is undertaken to evaluate the economical benefits that could be drawn from such a proposed barrier material. When compared to a conventional compacted sand-bentonite barrier with 12% bentonite concentration, it is found that the benefit realized could be estimated to 98, 96 and 90% when using PP material that contains 0.10, 0.20 and 0.5% of SAP. From this study, it can be concluded that PP materials show encouraging performance properties for barrier design.

[1]  Mamadou Fall,et al.  Modeling the effect of sulphate on strength development of paste backfill and binder mixture optimization , 2005 .

[2]  R. Kerry Rowe,et al.  Eleventh Canadian Geotechnical Colloquium: Contaminant migration through groundwater—the role of modelling in the design of barriers , 1988 .

[3]  J. O. Leppinen,et al.  Flotation in acid mine drainage control: Beneficiation of concentrate , 1997 .

[4]  Craig H. Benson,et al.  Hydraulic Conductivity of Compacted Clay Frozen and Thawed In Situ , 1993 .

[5]  Bo Elberling,et al.  A combined kinetic and diffusion model for pyrite oxidation in tailings: a change in controls with time , 1994 .

[6]  Mamadou Fall,et al.  Mix proportioning of underground cemented tailings backfill , 2008 .

[7]  T B Edil,et al.  Liners for waste containment constructed with class F and C fly ashes. , 2000, Journal of hazardous materials.

[8]  S. Karickhoff,et al.  SORPTION OF HYDROPHOBIC POLLUTANTS ON NATURAL SEDIMENTS , 1979 .

[9]  A. Shafiee,et al.  Permeability of compacted granule–clay mixtures , 2008 .

[10]  G. M. Ritcey.  Tailings management in gold plants , 2005 .

[11]  Michel Aubertin,et al.  Hydraulic conductivity of homogenized tailings from hard rock mines , 1996 .

[12]  D C Sego,et al.  Laboratory properties of mine tailings , 2001 .

[13]  Moir D. Haug,et al.  Cyclical closed-system freeze-thaw permeability testing of soil liner and cover materials , 1991 .

[14]  I. Paspaliaris,et al.  Potential use of lignite fly ash for the control of acid generation from sulphidic wastes. , 2002, Waste management.

[15]  Rens B. M. Verburg,et al.  USE OF PASTE TECHNOLOGY FOR TAILINGS DISPOSAL: POTENTIAL ENVIRONMENTAL BENEFITS AND REQUIREMENTS FOR GEOCHEMICAL CHARACTERIZATION , 2001 .

[16]  E. Yanful,et al.  Hydraulic conductivity of bentonite permeated with acid mine drainage , 2001 .

[17]  B. Elberling,et al.  Field determination of sulphide oxidation rates in mine tailings , 1996 .

[18]  K D Eigenbrod,et al.  Self-healing in fractured fine-grained soils , 2003 .

[19]  M Rico,et al.  Reported tailings dam failures. A review of the European incidents in the worldwide context. , 2008, Journal of hazardous materials.

[20]  Robert P. Chapuis,et al.  SAND-BENTONITE LINERS: PREDICTING PERMEABILITY FROM LABORATORY TESTS , 1990 .

[21]  D H Zou,et al.  Suitability of mine tailings for shotcrete as a ground support , 2004 .

[22]  Petra Schlager.  Sustainable Improvement in Safety of Tailings Facilities , 2004 .

[23]  J. L. Daniels,et al.  Durability of Boston Blue Clay in Waste Containment Applications , 2003 .

[24]  Henry Jean Claude Celestin.  Geotechnical properties of cemented paste backfill and tailings liners: Effect of mix components and temperature , 2009 .