2.2 Bulk chemical analysis.
Aliquots for chemical analyses were centrifuged for 5 min at 3000 rpm. After this step, the supernatant was withdrawn and replaced by Milli-Q-grade water to remove salts.
This rinsing step was repeated three times. The remaining pellet was freeze-dried (SGD-SERAIL, 0.05–0.1 mbar, -30 to 30°C, 48 h run) and weighed three times (Sartorius MC
210 P balance, precision of 10-4 g) to calculate the total mass. The particulate material was then ground to a fine powder and used for further elemental analysis.