Adsorption of Sudan IV from oily wastewater by using modified activated carbon materials
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abstract
A commercial activated carbon (AC: Norit ROX 0.8, D = 0.8 mm) was modified by chemical and thermal
processes, following the procedures described elsewhere [1]. The materials were tested as adsorbents
for the removal of a lipophilic pollutant, Sudan IV (S-IV), using a biphasic medium (water/cyclohexane)
in order to simulate contaminated petroleum mixtures with water [2]. The AC was modified in successive
steps considering: (1) grinding and sieving (< 250 μm) and (2) treatment with nitric acid, followed by
hydrotreatment with urea and thermal treatment at 800 ºC under inert atmosphere, resulting in the
adsorbents PAC and PACNAUT, respectively. Adsorption experiments were performed in a 500 mL
batch glass reactor, using 2.5 g of adsorbent per litre of organic phase, 2.5 g/LOP. Fig.1A shows results
with different particle size (ps), initial S-IV concentration (CS-IV,0) and AC modifications. As expected, it
can be observed that adsorption is faster when ps is smaller. However, the powdered activated carbon
(PAC) is not able to adsorb all S-IV in high initial concentration (500 mg/L). This target was achieved
with PACNAUT (adsorption of S-IV was 90 % at 1 h and 2.5 g/LOP of adsorbent, higher than the removal
observed by other authors [2] at the same time and 4 g/LOP of material). The adsorption kinetics was
fitted by a pseudo-second-order model to the data obtained with 500 mg/L of CS-IV,0 (Fig. 1B). PACNAUT
has higher adsorption capacity (qe) and rate constant (kS).
