الملخص الإنجليزي
Oil produced water (OPW) is produced in huge quantities with limited use for reinjection in oil
wells. This study aims to remove the dissolved oil in terms of chemical oxygen demand (COD)
using hydrophobic activated carbons. Activated carbon (AC) was prepared from date palm leaflets
using NaOH activation. AC was oxidized using concentrated nitric acid, ammonium persulfate,
and hydrogen peroxide to produce ON, OS, and OH, respectively. Alkyl amines including
methylamine (M), dimethylamine (DM), ethylamine (E), diethylamine (DE), and diisopropyl
amine (DIP) were covalently immobilized onto the oxidized carbons to produce hydrophobic
activated carbons via amide coupling. Thermogravimetric analysis (TGA) and Fourier Transform
Infrared (FTIR) show that the immobilization of alkyl amine onto oxidized activated carbons has
a covalent nature. AC possesses a high surface area (588) m2
/g, however, after oxidation and
surface functionalization, the surface area tremendously decreased following the OH > OS > ON
order which is the opposite order of oxidizing agents' power. After functionalization, surface area
and methylene blue (MB) adsorption followed the order of ON series > OS series > OH series as
the percentage of functionalization followed the order of ON series > OS series > OH series. Due
to the high content of -COOH of ON, not all –COOH groups were functionalized due to surface
crowdedness. The unfunctionalized content of –COOH act as hydrophilic barriers between
immobilized chains preventing their adsorption or interaction, unlike the OS series or OH series.
Thus ON series (ONM, ONDM, ONE, ONDE, and ONDIP) in addition to AC and ON were
selected for the treatment of MB. Only AC, ONDM, ONE, and ONDIP were tested for the removal
of aniline blue (AB) and dissolved organics as COD from OPW. pH 7 and pH 5 were found
optimum for the adsorption of MB and AB, respectively. The adsorption of both dyes was faster
on hydrophobic carbons than AC, following a pseudo-second-order kinetic model with the rate of
adsorption increasing with temperature rise. The activation energy, Ea, was < 42 kJ/mol indicating
physical adsorption. Equilibrium adsorption follows L-type isotherms with the adsorption data
fitting well with the Langmuir model. The adsorption capacity for MB follows the order of ONDIP
> ONE > ONDM > AC > ON > ONM > ONDE, while for AB, follows the order: AC > ONDIP >
ONE > ONDM. The thermodynamic parameters showed spontaneous and endothermic adsorption.
Carbon reuse showed better performance for hydrophobic activated carbons than AC.
OPW from Marmul plant (MP sample) is a field sample (COD 1422 mg/L), while Al-Fahl Plant
sample (FP) represents OPW that was separated from oil during transport to Al-Fahl Plant for
exportation (COD 19863 mg/L). MP OPW was completely treated using carbon adsorption, unlike
FP OPW which required FeCl3 flocculation before carbon adsorption because of its high COD
content. For MP sample, the optimum pH for the adsorption was found to be 7.9. ONE shows a
faster removal of COD than AC. The adsorption of COD follows the pseudo-second-order kinetic
model with an enhanced rate of adsorption as the temperature rises. Ea was < 42 kJ/mol indicating
physical adsorption and diffusion-controlled processes. Successive adsorption of COD from MP
OPW shows 100 % removal in the third adsorption cycle while for AC it reaches 85 % removal.
COD in FP sample was coagulated using FeCl3 removing 93.64 % of COD. The residual COD
(1262 mg/L) was efficiently treated using ONE showing 99.81 % of COD removal on successive
adsorption in the second cycle. The overall COD removal from FP OPW reached 99.99 % with the
treated water suitable for use in agriculture in terms of COD.
