Removal of Oil from Industrial Wastewater Using Organoclay Prepared From Iraqi Bentonite

The present study deals with the removal of oil from wastewater by organoclay. The organoclay was prepared by combination of Iraqi bentonite with quaternary amine (hexadecyltrimethyl ammonium chloride). The wastewater used in this study taken from the washing unit of fuel oil in the "South Baghdad Gas Power Plant". The operating conditions of batch process for removal of oil from wastewater by using the prepared organoclays were studied in details (quantity of organoclay, mixer speed and time of adsorption). Initial concentration of wastewater used in this study was within the maximum range 230-1512 mg/L. XRD and FTIR diagram of the prepared organoclay showed considered differences from those for natural bentonite which indicates the exchange of quaternary amine with Ca ++ ions at the surface of bentonite. The concentration of oil in the wastewater decreased less than 10 mg/L after treatment with organoclay. Batch kinetics studies were conducted by using kinetic equations (Lagergren and Ho et al) and batch isotherm studies was conducted by using isotherm models (Freundlich, Langmuir and BET). Journal of Petroleum Research & Studies

Adsorption is very efficient, cost effective and most importantly has the capability of meeting the environmental compliance as far as the discharge standard of the oil content of the wastewater is concerned [6]. Activated carbon is a common adsorbent used for the removal of hazardous pollutants from aqueous solutions. However, activated carbon adsorption is a nonselective process [5]. Organoclay has emerged as a better substitute for activated carbon. In fact, studies show that if a comparison is made between the organoclay and activated carbon, organoclay has several advantages over the activated carbon as an adsorbent [3].
Organoclays are manufactured by modifying bentonite (which is a kind of smectite group clay mineral, is almost made up of 80 wt.% of montmorillonite and contains a crystal lattice with three layers) or other clays with quaternary amines, thus changing the hydrophilic nature of clays to organophilic. Quaternary amine is a type of surfactant that contains a nitrogen ion. The nitrogen end of the quaternary amine (i.e., the hydrophilic end) is positively charged and

E 83
ion exchanges onto the clay platelet for sodium or calcium [14].
Powdered bentonite was used organoclay to remove oil from water.
The concentrations of oil in oily waters varied from 26 to 381 mg/L. The results indicated that the organoclay can remove up to 100% oil from oil in water emulsions [16]. Consequently, the organoclay could be considered an excellent media for treating oily waters. the synthesis of oranoclays by the ion exchange of sodium in Wyoming Na-Montmorillonite was investigated with three surfactants octadecyltrimethylammonium bromide (ODTMA), C 21 H 46 NBr, didecyldimethylammonium bromide (DDDMA), C 22 H 48 BrN, and )dihydrogenated tallow) dimethylammonium chloride (tallow) [7].
The organoclays were tested for hydrocarbon adsorption (diesel, hydraulic oil and engine oil), that are likely to be involved in landbased oil spills. Greater adsorption was obtained if the surfactant contained two or more hydrocarbon long chains.
The aim of the present research is to study the removal of oil from wastewater produced from washing unit of "South Baghdad Gas Power Plant" by using bentonite organoclay. The organoclay was prepared by modifying Iraqi bentonite by quaternary amine (hexadecyltrimethyl ammonium chloride solution 25% wt./vol.). The operating conditions for oil removal were studied in details. Kinetics and adsorption isotherm were also predicted.

Oily Water
The oily water was taken from the washing unit of fuel oil in the South Baghdad Gas Power Plant. Oil concentrations used in this study were within the maximum range (230-1512 mg/L). The characteristics of oily water are shown in Table (1). The bentonite used in this study was calcium bentonite powder from the State Company for Geological Survey and Mining (Iraq).
The characteristics of the bentonite are presented in Table (2).

Hexadecyltrimethyl Ammonium Chloride
This material which is one type of a surfactant was used to modify bentonite from hydrophilic nature to organophilic. It is produced by Indian Company (Unilab Chemicals and Pharmaceuticals

Synthesis of Organoclay
Organoclay was produced by adding the required quantity of hexadecyltrimethy ammonium chloride solution (25% wt./vol.) to the desired quantity of bentonite (particle size of 0.075 mm) in a stainless steal container and mixed thoroughly by hand. The produced paste was then introduced into the meat grinder and the product was collected in a container. The reacted material (organoclay) is then dried in the electrical oven at 60 °C for 48 hours and then ground by agate mortar followed by screening to particle size of 0.075 mm.

E 86
Organoclay with ratios of 10, 20, 30, 38 g amine/ 100 g bentonite was prepared in this study to find the best ratio of amine to bentonite that gives the highest oil removal efficiency.

Oil Removal from Wastewater
One liter of oily water was first placed into a beaker and a desired quantity of prepared organoclay was then added to the beaker.
The materials were mixed using an electrical mixer at adjustable mixer speed for the required time. Then the slurry was filtered using vacuum filtration unit to separate organoclay from treated water. The filtrate was used for oil concentration measurement using partition graphmetric method 5520B [19].

Infrared Curves
The absorption of infrared radiation by clays was recorded over a range of 4000 to 400 cm -1 as shown in figs.

Effect of Quantity of Bentonite on Oil Removal
The ability of bentonite to remove oil from wastewater was adsorbed by montmorillonites due to their reduced solubility in water [5].

Effect of Quantity of Organoclay on Oil Removal
The prepared organoclays with quaternary amine weight ratio of 10, 20, 30 and 38 g/100g bentonite were investigated to find the quantity of organoclay required to remove the greatest amount of oil from wastewater. Figure 6 shows the effect of quantity of organoclay and much more organoclay must be added to remove extra amount of oil, also the oil concentration difference between the bulk of the liquid and the surface of the organoclay, which causes a driving force for oil adsorption, is decreased causing a decrease in adsorption rate, so another surface of organoclay was used must be added to overcome this problem [17].

E 93
Organoclay to remove oil from produced water (a byproduct of oil and gas production) and they reach oil removal efficiency of 97% [16].
Same results were obtained for initial oil concentration of (255

Effect of Amine to Bentonite Weight Ratio on Organoclay & Adsorption of Oil
In order to show the effect of weight ratio of amine to bentonite on oil removal, the equilibrium oil concentration of treated water was plotted against amine to bentonite weight ratio, fig.(8) . Mixer speed used for these experiments was 450 rpm, time 1 hour, quantity of prepared organoclays 20g for amine ratio 10 g amine/100g bentonite and 15g for amine ratios 20, 30 and 38 g amine/100g bentonite. One liter of wastewater was used with initial concentration of (1450 -1512) mg/L. It can be seen clearly from fig. (8) that the ratio of amine to bentonite has a large effect on the oil removal efficiency

E 95
where the concentration of oil decreases from 117 to 8.8mg/L as the amine ratio in organoclay increases from 10 to 38g amine/100g bentonite. The best amine ratio was 30g amine/100g bentonite, where oil concentration falls to 1 mg/L. where the best amine ratio was 30g amine/100g bentonite for which oil concentration falls to 1 mg/L.         The results of the effect of mixer speed is not surprising, where oil concentration decreases as mixer speed increases due to the decreasing in the resistance to mass transfer for oil from bulk of the wastewater to the surface of organoclay. The resistance to mass transfer is due to the diffusion layer surrounding each particle of organoclay. The mass transfer mechanism for oil adsorption by organoclay is a two phase process and can be described as diffusion of oil from the oil-water emulsion to the surface of the organoclay and the adsorption of oil within the pore structure of the organoclay [17].

Batch Kinetics Study
The plots of oil concentration versus time for initial oil concentration 1512 and 230 mg/L are shown in figs. (12)(13), respectively. In these experiments 15g organoclay of 30g amine/100g bentonite was added to 1 liter of wastewater and mixer speed fixed at 450 rpm.
From these plots, the equilibrium time was found to be 30 minutes for both concentrations. Also, it can be seen from these plots

E 101
Batch kinetic data was fitted to the Lagergren eq. (2)

……………………………… (4)
Where: x = mass of solute adsorbed to the solid (mg);  The values of parameters in the isotherm models applied to oily waters are presented in Table (9).  of 450 rpm to reduce the concentration of oil below 10mg/L which is the standard limit for discharge oily wastewater.