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Retention of calcium ions by thermically modified materials from soils of San Juan de Lagunillas, Mérida, Venezuela

Abstract:

The present work focus on the calcium retention potential of some litologic materials from soils of Merida state, Venezuela, after progressive thermal treatment from 20°C to 800°C during 3 h. X ray difraction shows presence of iron and aluminium oxides which participate in the exchange reactions. The protonation reaction generates 28.35 cmol (+) kg-1 of positive charges and the deprotonation reaction produces 35.35 cmol (-) kg-1 of negative charges. The analysis made upon the original materials shows cationic exchange capacities "CEC" ranging between 5-19 cmol (+) kg-1. Portion of the of the CEC used in the retention of calcium from water ranges 2-7% because of the bases saturation, so the amounts of calcium retained are associated with the empty CEC. The exchanging performance is improved by dislodging calcium from the exchanging sites with NaCl 0.05 N solution before reuses, obtaining up to 36% from the original CEC used. Results show that these materials could be used in water softening.