1994-02-28_REVISION - M1988112 (2)

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SOLID PHASE CHARACTERIZATION of rinse vat er van added to the upper eactian. Af tar the water rose into cha standpipe, it vas drawn through the aolida, glaa^ fiber filter, pleat is place, a 0.45 edcron l11111po re filter, and into a receiving flank under a vacuum of 4 Snchee (10.2 cm) mercury. - the rinse water, or drainage, va9 analyzed for specific conductance, pH, alkal inicy, acidity, copper, ^1cke1, cobalt, zinc, iron, calcium, and sulfate. The volume of rinse water, spec if lc conduccanca, pH, alkalinity, and/or ac idlty were determined weekly, and su if ace vas analyz nd biweekly. trace metals (Cu, Ni, Co, Zn), Fe, Ca, end Hg ve re analyzed biweekly for the first 20 weeks and monthly sub sequen[ly. Analys le The sulfuC content of [he rock vat determined by LECO furnace and the neutrallzat Sort potential vas determined by the method of Sobek e[ al. (1978). For aqueous solutions, epecif is conduc- tance vat analyzed ua ing a Nyron L conductivity mace r, while either a Aad Lometer 29 or an Orion SA 720 meter vat used for pH analy se e. Alkali- nity and acidity were analyzed using standard techniques for endpoints of 4.5 and B.J, re spectlvely (APNA et al., 1975). He[ale were analyzed with a Perkin Elmer 603 atomic absorp- tion apectrophotomete r. Sulfate vat analyzed using [he barium sulfate Curb ldlme [ric technique (APHA et al., 1915). to 9 /~~ x f e. g 1 150 l00 .~ e 50 7hna 4wslkd S3 Figure 1, pH, and gulf ace, calcium and magmas i,m concentrations vs. time Eor weeks L through 20. RESULTS AND DISCUSSION During the characterization of mining vaatee, some vae[ea may be ldentlf ied ae acid producing based on an extreme excess of iron sulfide content relative co buffering mineral content. Similarly vastee devoid of iron sulfide or with an extreme excess of buffering mineral content over Sron sulfide content can be lden[lf lab le as non-acid producing. Other ac Sd producers may be Sden[if ied based on acidic drainage generated during the experimental time frame of klnecit caste. wastes which produce alkaline drainage during the kinetic [e9te may have produced acidic drainage attar the buf faring minerals ve re depleted in a Lomger experiment. The results of 20 wanks of kinetic testing provide such an example. Over [his period the drainage pH vat in the range of 1.8 co 9.5. The excessively high pH Le due [o the presence of some lime (Ca0) in [he RK fines. In experiments conducted with mixtures of lime scone and rock, Eev values exceeded pH 9.0. She concentrations uF sulfate and calcium in the initial rinse (t 0) were l70 and 360 mg/L, re spectlvely. During [he initial four veaka these concentrations decreased, suggesting they were products of oxidac ion during storage prior co the experi- ment. From week 5 [0 20 [bey were typically more stable in a lover concentration range (figure 1). Based on the pH data over this period alone, this solid would not b• elaeslf ied as an acid produtar. To determine the potential for each solids to produce acid drainage it Se okceeeary [o quantify the times required to deplet ai the acid producing iron sulf Ides and the ac Sd nedtrallz ing carbonate minerals. Calculac ion of these times requires the Snlt iel cons en[ of cheat ^inarala in [ha vaete and the rates at which Rhay ere depleted (f. e., the recta of acid production and acid consumption). The iron eulf Sjde content van calculated based on the sulfur and trace metal contence in con]unet ion with Itha knowledge that virtually all sulfur in this rock 1a present ea sulf Ides (1. e., no sulfates). Shia calculation Ind icated cha presence of 46 mi111molae of Sulfur in the AK fines rock mizture. The carbonate mineral content vas calculated based on an ad]ustment to th• analyzed neutrali- zation potential. The method of Sobek ec al. (1918) vas used co determine the nautraliz anon potential. The strong acid deed Sn this method may dissolve minerals which ould not consume acid under conditions typlca~ of environmental dLsso lut ion (Lu[vick, 1986). Tha neutralizac ion potential determined by chit method may also be overeat imatad dun to contribatdans from metal hydroxides vhieh precipitate during the beck titration (Fe rgueon and Erickson, 1988). o ~ s lu is au o