Abstrait

Physicochemical characterization and rheological study of Tunisian palygorskite

Mouna Touati, Memia Benna-Zayani, Hammadi Nciri, Malika Trabelsi Ayadi, Najia Kbir Ariguib

The studied clay is collected fromthe Tataouine Douiret area of the Tunisian south. The layer contains 50%of clay fraction and 50%of impurities formed essentially from calcite and quartz. The cation exchange capacity (CEC) of purified clay is 43 meq/100g of burnt clay. The physico-chemical characterizations of the clay have shown that it is fibrous clay and particularly it is a palygorskite. The thermal analysis of rough and purified clay has demonstrated that the departure of zeolitic water is carried out at 118ï‚°C. The deshydroxylation is occurred at 501ï‚°C for the rough palygorskite and at 484ï‚°C for the purified palygorskite. The study of the effect of the mass percentage of clay on the rheological properties has shown that the flow curves have Newtonian behaviour for clay fractions lower than 14%(w/w). The effect ofNaCl on the rheological behaviourwas studied for clay fractions 1.5, 3.25 and 14%(w/w). Concerning the first two clay fractions, the critical flocculation concentration (Ck) is noted at 0.05% of NaCl. For gel (clay 14%), a jump of viscosity is observed from 0.07% of NaCl. From 0.2% of NaCl a very rigid gel is obtained which persists even for high electrolyte percentages.