2.6.3. Cleaning experiments
The cleaning procedure depended on the aim of the test, since
partial cleanings were required according to the goals of this work.
Table 1 details the three different procedures carried out in concordance
with the above mentioned objectives. The general procedure
included a first rinsing step with distilled water, a chemical cleaning
step and a final rinsing step (in continuous feed mode) until
distilled water characteristics were reached.
The first rinsing step was carried out at 25 C, at transmembrane
pressure of 1 bar, at cross flow velocity of 2.2 m/s during
30 min (only during the first 5 min, this step was carried out in
continuous feed mode). Flux was measured every 5 min.
The chemical cleaning step (with NaOH or P3 Ultrasil 115 solution)
was carried out at a transmembrane pressure of 1 bar and at a
cross flow velocity of 2.2 m/s during 30 min and in total recycle
mode. The optimum conditions of temperature and concentration
of the cleaning solutions were chosen according to previous studies
(Luján-Facundo et al., 2013). Thus, the tested temperature and
concentration were 45 C and 0.4 103 g/l (pH 9) for NaOH solution
and 35 C and 0.7% v/v (pH 12.73) for Ultrasil solution.
Each experiment was repeated at least twice, but if the results
differed significantly, the experiment was repeated three times
and the mean values were reported. Results were reproducible.
2.6