Kaolinite analysis of Weipa bauxite using near infrared spectroscopy

The objective of the study was to develop a near infrared spectroscopic system to quantify kaolinite in Weipa bauxites and compare it to Rio Tinto Aluminium's existing PIMA II system. Two candidate systems were trialled based on different instrument technologies, FTNIR and pre-dispersive grating NIR. The FTNIR system proved superior in terms of accuracy, throughput and ease of use quantifying kaolinite with an accuracy of 0.89 %m/m for a 9 second measurement. This system offers nearly 100% improvement in accuracy and increased throughput compared to the existing PIMA II system.

Calibrations were also developed for gibbsite, boehmite, hydrohematite, goethite, loss on ignition and total available alumina. Calibrations were successful with accuracies of 1.9, 1.7, 0.94, 0.11, 0.75 and 3.2 %m/m, respectively, and R2 values greater than 0.95.