**5. Motivation for the removal and sorption Fe3+ ions**

In practice form recent studies, the natural zeolite [19], activated carbon[36], olive cake [21], quartz and bentonite [20] and jojoba seeds [37] are used as an adsorbent for the adsorption of mainly trivalent iron ions in aqueous solution. The Motivation for the removal and sorption Fe3+ ions is that iron ions causes serious problems in the aqueous streams especially at high levels concentration [38 - 39]. Usually, the iron ions dissolve from rocks and soils toward the ground water at low levels, but it can occur at high levels either through a certain geological formation or through the contamination by wastes effluent of the industrial processes such as pipeline corrosion, engine parts, metal finishing and galvanized pipe manufacturing [40 - 41].

The presence of iron at the high-levels in the aqueous streams makes the water in unusable for an several considerations: Firstly, Aesthetic consideration such as discoloration, the metallic taste even at low concentration (1.8 mg/l), odor, and turbidity, staining of laundry and plumbing fixtures. Secondly, the healthy consideration where the high level of iron ions precipitates as an insoluble Fe3+-hydroxide under an aerobic conditions at neutral or alkaline pH [42]. This can generate toxic derivatives within the body by using drinking

In order to fully understand the nature of adsorption the thermodynamic parameters such as free energy change (Gº) and enthalpy change (Hº) and entropy change (Sº) could be calculated. It was possible to estimate these thermodynamic parameters for the adsorption reaction by considering the equilibrium constants under the several experimental

G = R lnKd(T) (14)

lnKd = S/R – H/RT (15)

 G = H – TS (16) The Kd value is the adsorption coefficient obtained from Langmuir equation. It is equal to the ratio of the amount adsorbed (x/m in mg/g) to the adsorptive concentration (y/a in

These parameters are obtained from experiments at various temperatures using the previous equations. The values of Hº and Sº are determined from the slop and intercept

In general these parameters indicate that the adsorption process is spontaneous or not and exothermic or endothermic. The standard enthalpy change (Hº) for the adsorption process is: (i) positive value indicates that the process is endothermic in nature. (ii) negative value indicate that the process is exothermic in nature and a given amount of heat is evolved during the binding metal ion on the surface of adsorbent. This could be obtained from the plot of percent of adsorption (% Cads) *vs.* Temperature (T). The percent of adsorption increase with increase temperature, this indicates for the endothermic processes and the opposite is correct [35]. The positive value of (Sº) indicate an increase in the degree of

In practice form recent studies, the natural zeolite [19], activated carbon[36], olive cake [21], quartz and bentonite [20] and jojoba seeds [37] are used as an adsorbent for the adsorption of mainly trivalent iron ions in aqueous solution. The Motivation for the removal and sorption Fe3+ ions is that iron ions causes serious problems in the aqueous streams especially at high levels concentration [38 - 39]. Usually, the iron ions dissolve from rocks and soils toward the ground water at low levels, but it can occur at high levels either through a certain geological formation or through the contamination by wastes effluent of the industrial processes such as pipeline corrosion, engine parts, metal finishing and galvanized

The presence of iron at the high-levels in the aqueous streams makes the water in unusable for an several considerations: Firstly, Aesthetic consideration such as discoloration, the metallic taste even at low concentration (1.8 mg/l), odor, and turbidity, staining of laundry and plumbing fixtures. Secondly, the healthy consideration where the high level of iron ions precipitates as an insoluble Fe3+-hydroxide under an aerobic conditions at neutral or alkaline pH [42]. This can generate toxic derivatives within the body by using drinking

*Kd* = (x/m). (y/a) (17)

**4.4 Thermodynamics parameters for the adsorption** 

mg/dm3)

of the linear plot of (*ln Kd*) vs. (1/T).

freedom (or disorder) of the adsorbed species.

pipe manufacturing [40 - 41].

**5. Motivation for the removal and sorption Fe3+ ions** 

conditions. They can calculated using the following equations [34]:

water and can contribute to disease development in several ways. For instance, an excessive amounts of iron ions in specific tissues and cells (iron-loading) promote development of infection, neoplasia, cardiomyopathy, arthropathy, and various endocrine and possibly neurodegenerative disorders. Finally, the industrial consideration such as blocking the pipes and increasing of corrosion. In addition to that, iron oxides promote the growth of microorganism in water which inhibit many industrial processes in our country [43].

In response to the human body health, its environmental problems and the limitation water sources especially in Jordan [44], the high-levels of Fe3+ ions must be removed from the aqueous stream to the recommended limit 5.0 and 0.3 ppm for both inland surface and drinking water, respectively. These values are in agreement with the Jordanian standard parameters of water quality[45]. For tracing Fe3+ ions into recommended limit, many chemical and physical processes were used such as supercritical fluid extraction, bioremediation, oxidation with oxidizing agent [46]. These techniques were found not effective due to either extremely expensive or too inefficient to reduce such high levels of ions from the large volumes of water [47 - 48]. Therefore, the effective process must be low cost-effective technique and simple to operate [49 - 52]. It found that the adsorption process using natural adsorbents realize these prerequisites. In addition to that, the natural adsorbents are environmental friend, existent in a large quantities and has good adsorption properties. The binding of Iron(III) ion with the surface of the natural adsorbent could change their forms of existence in the environment. In general they may react with particular species, change oxidation states and precipitate [53]. In spite of the abundant reported researches in the adsorption for the removal of the dissolved heavy metals from the aqueous streams, however the iron(III) ions still has limited reported studies. Therefore our studies are concentrated in this field. From our previous work, the natural zeolite [19], quartz and Bentonite [20], olive cake [21], in addition to the chitin [24], activated carbon [54 - 55] and alumina [56] have been all utilized for this aspect at low levels. The adsorption isotherm models (Langmuir and Freundlich) are used in order to correlate the experimental results.
