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Table 3 Dissolution screening at pH 7.4 and pH 4.5. “Ions” = cumulated dissolved Si and Al based on ICPMS quantification of all eluted ions, in % of initial Si and Al; “S” = remaining solid mass, in % of initial MMVF mass; “k” = dissolution rate determined from cumulated dissolved ions, in ng/cm2/h

From: Composition, Respirable Fraction and Dissolution Rate of 24 Stone Wool MMVF with their Binder

  screening at pH 4.5 screening at pH 7.4 pH4.5, (binder removed) pH4.5 (milled) pH4.5 respirable (milled + cyclone) pH4.5 (1/5 lower SA/V)  
  Ions (%) S (%) k Ions (%) S (%) k k k k k SEM morphology before and after after dissolution (full data in SEM Annex)
MMVF #17 (pre-1995) 2 95 9         Untreated – smooth surface
pH4.5 - very limited change of fibre surface after treatment: minimal roughening, no significant gel formation, no leaching pits.
MMVF #1 11 85 90 4 94 31     171 Untreated - binder covers entire fibre, including 100 nm to 1 μm sized particles.
pH4.5 - Very limited change of fibre surface after treatment: occasionally approx. 50 nm small leaching pits (pores).
pH7.4 – significant change of fibre surface, approx. 200nm to 1 μm gel/deposit/crater structures
MMVF #2 9 96 23         Untreated - smooth surface, occasional lumps of 100 nm to 1 μm sized particles.
MMVF #4 10 100 20 7 92 17 39     Untreated – smooth surface
pH4.5 – very significant change of fibre surface with pronounced gel; frequent occurence of approx. 400nm sized deep craters with sub-100-nm cracks at bottom.
pH4.5 – without binder, change of fibre surface with limited gel, no cracks, no pits, but approx. 200nm sized shallow structures. Thermal removal more effectiove than plasma removal of binder.
pH7.4 - very significant change of fibre surface with pronounced, inhomogenously structured gel and/or deposits, up to approx. 400nm large crater
MMVF #5 10 85 87 4 97 35   104 122   Untreated – smooth surface, occasional lumps of 100 nm to 1 μm sized particles.
pH4.5 - significant change of fibre surface with extensive gel formation, leaching with sub-100-nm sized pits and cracks. pH4.5 on respirable-only fraction also induces gel formation, leaching with sub-100-nm sized pits
pH7.4 - significant change of fibre surface, inhomogeneous leaching through gel with 1-μm-diameter honeycomb structures.
MMVF #7 11 94 40 2 99 6 58     Untreated – smooth surface, occasional 200 nm sized particles
pH4.5 – significant change of fibre surface with extensive gel formation, up to 4 μm sized leaching pits, occasional micro-cracks and approx. 100 nm large pores.
pH4.5 – binder removed thermally: no significant gel formation, occasional micro-cracks (intermediate gel formation if binder removed by plasma)
pH7.4 – very significant change of fibre surface with gel formation and/or deposits of up to approx. 2 μm large crystalline particles
MMVF #8 10 97 65         Untreated – smooth surface. Binder covers entire fibre (see ruptured crossings).
pH4.5 –significant change of fibre surface with gel formation, numerous up to approx. 100 nm sized leaching pits (pores).
MMVF #11 13 85 58         Untreated – smooth surface, occasional lumps of 200 nm to 1 μm sized particles
pH4.5 – very significant change of fibre surface with gel formation and deep micro-cracks (3μm x 300nm). Pitting (approx. 1 μm large spots) and approximately 200nm visible pores
MMVF #12 6 93 36 4 94 27   31 29   Untreated – rough surface, lateral cracks
pH4.5 – significant change of the fibre surface, increased smoothness. No significant gel formation, no leaching pits; pH 4.5 on respirable-only fraction: limited gel formation, no significant leaching pits.
pH7.4 – significant change the fibre surface with pronounced gel formation, inhomogenous leaching, approx. 4μm x 0.5μm sized leaching pits
MMVF #14 8 90 24 4 93 12      Untreated – binder covers entire surface, frequent inclusion of approx. 100 nm sized particles
pH4.5- significant change of fibre surface with gel formation, inhomogenous leaching, up to approx. 500 nm large leaching pits, occasionally up to approx 200 nm wide pits/pores.
pH7.4 – very significant change of fibre surface with fine grained deposits of approx. 100 to 500 nm sizes.
MMVF #20 7 89 49         Untreated – smooth surface, binder covers entire surface
pH4.5 – significant change of fibre surface with gel formation and erosion by frequent approx. 50 nm sized leaching pits/pores
MMVF #21 7 99 23         Untreated – smooth surface, very rare inclusion of approx. 200 nm sized particles
MMVF #22 5 91 17 5 95 15      Untreated – smooth surface with inclusion of approx 250 nm sized particles.
pH4.5 – significant change of fibre surface with gel formation; up to 1.5 μm diameter plateaus that have an up to 1 μm long micro crack in their center.
pH7.4 – significant change of fibre surface with gel formation, approx. 500nm diameter leaching crater
MMVF #24 9 91 28         Untreated – smooth surface with occasional inclusion of approx 500 nm particles
pH4.5- very significant change of fibre surface with 2 μm diameter plateaus with several approx 50 nm leaching pits on the plateaus
MMVF #26 4 93 18         Untreated – structured surface with approx. 200 nm to 1μm diameter elevations.
pH4.5 – significant change of fibre surface with gel formation, no leaching pits.