Immobilization of simulated evaporator concentrate waste

Abstract

Simulated evaporator concentrate was prepared by pre-treating sodium borate with calcium hydroxide to produce an insoluble, ulexute-like borate salt. The resultant solid waste was blended by extrusion with virgin and recycled low density polyethylene (LDPE) . Samples were evaluate to homogenity by density determinations (ASTM D792-91), compressive strength (ASTM D695-91) and leaching behavior by accelerated leaching tests (ASTM C1308-95). Coefficient of variation of density was lower than 5 percent for all evaluated waste forms, indicating a satisfactory homogeneity. Compressive strengths have compiled to U.S.NRC standard and were above CNEN standard limit for cement waste products if 5 percent strain could be considered a reasonable limit to assure the structural integrity of the material. Cumulated fraction leached after 11 days of accelerated leach test was found to be lower than 10 per centum and diffusion coefficients of boron have varied between 3.86 x 10-10 and 9.06 x 10-10cm2/s. Boron concentrations for all materials have shown a tendency to reach an symptotic value at the end of the test (around 0.25 and 0.7 mg/L for 30 and 50 percent waste load, respectively). Measured cumulated fraction leached (CFL) data with time have shown a tendency of becoming asymptotic sooner than it was predict by the diffusion model.