Thermal behavior of peloids prepared with mineral waters from Lanjarón Spa. Effect of maturation time

Abstract

The differences in the thermal behavior of peloids prepared with mineral waters from Balneario de Lanjarón (Salud V -samples S- and Capuchina -samples C-; with very different ionic contents) during the maturation process along to 1, 3 and 6 months, were studied. The solid phase was a mixture of kaolin-bentonite, proportion 9:1 (w:w). The drop in temperature of the peloid fits a logarithmic curve of the type y = aln(x) + b, where y = ΔT (ΔTºC, being ΔT = T0-Tn; T0= 65ºC) and x = time, with R2 > 0.9. These equations allowed us to estimate the time necessary to decrease 22.5°C temperature, T22,5ºC (min) (22.5° C being 75% of the total decrease of temperature in the experiment: 65 - 35° C). The T22,5ºC is maintained or increased slightly from one to three months of maturation and their magnitudes are similar between both types of samples. However, S6 and C6 show differences, with increases in C6 respect to C1 and C3, and decreases in S6 respect to S1 and S3. Thus, the cooling of the peloid is significantly faster in S6 regarding to C6. The study with SEM-IA revealed that the percentage of area occupied by the pores in the peloids varies significantly from the third month of maturation, although the behavior is different: in the samples S the fabric becomes less porous and in the C conversely. Furthermore there is a direct relationship between cooling rate and the area occupied by the pores of both peloids with increasing the time of maturation.