ISO 8008:2005

Overview

ISO 8008:2005 specifies an instrumental laboratory method to determine the specific surface area (SSA) of smelter‑grade alumina (aluminium oxide) used in primary aluminium production. The method uses nitrogen adsorption at liquid‑nitrogen temperature and the Brunauer‑Emmett‑Teller (BET) theory to calculate surface area. ISO 8008:2005 applies to aluminas with SSA in the range 50–90 m2/g and recommends a multi‑point BET analysis for greater accuracy (single‑point is permitted but gives lower results).

Key topics and technical requirements

• Measurement principle: adsorption of N2 at −196 °C to determine monolayer volume and derive SSA using BET theory.
• Degassing: samples degassed at 150 °C (vacuum or flowing N2). Vacuum system must maintain < 0.2 mbar; sample tubes must be sealed to avoid air ingress.
• Instrumentation: low‑temperature surface‑area analyser capable of multi‑point or single‑point BET determinations.
• Relative pressures: multi‑point analyses use P/P0 between 0.10 and 0.30; single‑point uses P/P0 = 0.30.
• Sample preparation:
  • Prepare a 50 g test sample by riffle/rotary divider.
  • Use an optimum test portion per instrument recommendations; minimum 0.2 g degassed sample mass.
  • Clean and dry sample tubes (ultrasonic bath and ethanol rinse recommended).
• Calculation: if instrument reports total surface area (S), SSA = S / m (m = degassed sample mass). Report SSA to the nearest whole unit.
• Quality control: include a reference alumina (example: ALU‑11) each batch; certified values for ALU‑11 are 67.8 ± 2.9 m2/g (single‑point) and 69.1 ± 2.3 m2/g (multi‑point).
• Precision: expected repeatability and reproducibility (95% confidence):
  • Single‑point: r = 0.8 m2/g, R = 2.1 m2/g
  • Multi‑point: r = 1.0 m2/g, R = 2.5 m2/g
• Reporting: reference ISO 8008, sample ID/date, SSA (whole unit), whether single‑ or multi‑point, QC results and unusual observations.

Applications and who uses this standard

ISO 8008:2005 is used by:

• Alumina producers and refineries for product specification and quality control.
• Aluminium smelters and downstream customers who require consistent feedstock properties.
• Analytical laboratories performing routine SSA testing.
• Equipment manufacturers (surface‑area analysers) and suppliers of reference materials. Practical applications include acceptance testing, process control, batch certification, and comparative QC using reference aluminas.

Related standards and references

• BET theory: Brunauer‑Emmett‑Teller adsorption model for SSA determination.
• ISO 8008:2005 is based on Australian Standard AS 2879.4‑2003 and cites AS 2850 (for precision testing guidance).
• Reference material example: Alcan ALU‑11 (used for batch quality control).

Keywords: ISO 8008:2005, aluminium oxide, alumina, specific surface area, nitrogen adsorption, BET, smelter‑grade alumina, surface‑area analyser, degassing, multi‑point, single‑point.