Removal of Ciprofloxacin Hydrochloride from Aqueous Solution by Pomegranate Peel Grown in Alziedab Agricultural Scheme-River Nile State, Sudan

Removal of Ciprofloxacin (CIP) antibiotic from aqueous solution onto Activated carbon derived from pomegranate peel wastes collected from Alziedab Agricultural Scheme at River Nile state, Sudan as a novel precursorby chemical activation with Potassium Hydroxide (KOH), at specific condition of carbonization temperature at 500°C and 1 hour as a holding time and detonated as (AC(PPZS)KOH. The obtained material was submitted to measurements of active surface area, Fourier Transform Infrared Spectroscopy (FTIR) analysis and scanning electron microscope (SEM). Batch-adsorption studied had been carried out to examine the adsorption capacity of the AC(PPZS)KOH for the removal of Ciprofloxacin from aqueous solution. The effect of various process parameters like pH, initial antibiotic concentration, adsorbent dose, and contact time, on the efficiency of Ciprofloxacin removal was investigated. Maximum adsorption of Ciprofloxacin on AC(PPZS)KOH, (86.4 ± 5.7%) was observed at pH 8. The optimum adsorbent dose was determined as 0.05 g at 25°C. Initial Ciprofloxacin concentrations has important effect on AC(PPZS)KOH in the studied range (50–300 mg/L) where the removal percentage increases as the antibiotic concentration decrease. The adsorption equilibrium data was well explained by Freundlich isotherm. The results reveal the Langmuir model is not able to describe the experimental data properly, poor less of fitting on AC(PPZS)KOH. The Freundlich isotherm experimental data obtained showed (Correlation Coefficient, R 2 = 0.991) higher than Langmuir isotherm, R 2 = 0.919). The porous characteristics and adsorption efficiencies of prepared AC(PPZS)KOH were also investigated.


Introduction
The removal of conventional pollutants, such as persistent organic pollutants was in focus for the last decades and so their behavior is well understood [1]. On the other side very little is known about the behavior of trace pollutants yet, which are present in the environment in extremely low concentrations. Pharmaceuticals are an example for the variety of man-made trace pollutants that are introduced in surface or subsurface water bodies [2]. Pharmaceuticals have been identified in the environment, including antibiotics, analgesics, psychiatric drugs, and natural and synthetic hormones [3]. Unused human pharmaceuticals may also enter the environment through landfill leachate [4,5].
Adsorbents such as charcoal [6], polymers [7] and bentonite [8][9][10][11][12] in adsorption of drug, are recognized in clinical practice and environmental treatment. The safety, high adsorptive capacity, and high specific surface, have been accepted for a long time.
Pharmaceuticals poisoning also has been defined as a condition produced by any substance which when swallowed, inhaled, injected or absorbed precutaneously is capable of causing death, injury, toxic or untoward reactions [13].
Ciprofloxacin hydrochloride (CIP) is a synthetic chemotherapeutic antibiotic (1-cyclopropyl-6-fluoro-1, 4dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid), Its empirical formula is C 17 H 18 FN 3 O 3 and its molecular weight is 331.4 g/mol. The broad spectrum antibiotic Ciprofloxacin (CIP) is used in human and veterinary medicine that is readily transported into the environment via domestic wastewaters and through direct runoff. (CIP) is a member of the Fluroquinolones antibiotics which is frequently used to the treatment of infections caused by bacteria aerobic like Klebsiella, Shigella which result in inflammation of the respiratory tract, inflammation of the ear, sinus, urinary tract, gonorrhea, inflammation of the skin and tissue infections and bone. In the event of over dose will cause poisoning and kidney pains and muscle acheate [14].
Adsorption of Ciprofloxacin from aqueous solutions by Pomegranate Peel wastes grown in Alziedab Agricultural Scheme (PPZS) has been studied in this work. Batch adsorption experiment were investigated to study the sorption behavior of (PPZS) towards Ciprofloxacin as a function of initial concentration, reaction time, adsorbent dosage and pH. Time dependent showed that the adsorption process reached equilibrium at 30 min. Two adsorption isotherms equations were employed including Freundlich and Langmuir. The equilibrium data could be well described by Freundlich equation for the adsorption on pomegranate peel waste.

Materials and Methods
The carbonaceous precursor used for preparation of activated carbon (AC) was Pomegranate Peel, collected from Alziedab Agricultural Scheme (PPZS) at River Nile State, Sudan. Prior to use, sample was washed gently several times with distilled water to remove impurities present on the surface and then dried for one week. All chemical reagents used in this work were BDH, used without further purification.

Preparation of Activated Carbon
Pomegranate Peel dried, crushed and grinded in a ball mill. The grinded sample was sieved to obtain particles ofuniform size90 mesh sieves. The precursor obtained was washed to remove surface bounded impurities and dried at 105°C for 24 h. 100g of the precursor was impregnated with potassium hydroxide, KOH for 24 h in ratio of 1: 1.5 at 50°C to achieve well penetration of the chemical into the interior of the precursor.
After impregnation, the sample was dried for 24 h at 105°C. Activation treatment was carried out in a Carbolite™ furnace at 550°C, using 25 g of the impregnated and dried sample. After cooling the solid residue to room temperature, washed with double distilled water followed by 0.1 M hydrochloric acid (HCl) to remove the residual chemical agents until the pH value of the rinsed water was neutral. The adsorbents prepared were denoted as AC(PPZS)KOH, throughout the work.

Ciprofloxacin Standardization and Wavelength Selection
Ciprofloxacin (CIP) used as adsorbate, obtained from Amipharama Laboratories Ltd, Sudan. A stock solution of 1000 mg/Lwas prepared by dissolving appropriate amount of (CIP) in1000 ml double distilled water in volumetric flask, different concentrations were prepared by diluting the stock solution to the initial concentrations ranging from 50-300 mg/L. Spectra of ciprofloxacin was measured by UV visible Jenway 7305 spectrophotometer, using 200 mg/L solution, scanned in the 200-300 nm UV regions. The maximum wavelength (λ max ) was observed at 274 nm which was adopted for absorbance measurement. Measurements of the absorbance of each standard solution (50, 100, 150, 200, 250 and 300 mg/L) in 1cm cuvette at 274 nm, using double distilled water as a blank to verify Beer's -Lambert law were carried out [32].

Evaluation of Activated Carbon
The activated carbon sample was evaluated two ways:

Fourier Transform Infrared Spectroscopy
The surface functional groups of the ACs were estimated by Fourier Transform Infrared (FTIR) spectroscopy (Shimadzu, Japan). FTIR spectra of the prepared AC(PPZS)KOH samples were recorded within 400 -4000 cm -1 . The transmission spectra of the samples were recorded using the KBr pellet. About 1.0 -2.0% of each sample was mixed with dry KBr and grinded in mortar. Then the samples were transferred to hydraulic press. The pellets which are homogeneous and transparent in appearance were dried overnight at 100°C, and then inserted into the IR sample holder for the analysis.

Scanning Electron Microscopy (SEM)
SEM analysis of samples was performed by using (JSM-6380LA) scanning electron microscope. The SEM instrument was operated at 5 kV/SE (Accelerating Voltage Machine), and 50°C inclination. Before analysis, all samples were ground and coated in a sputter coating unit (Edwards Vacuum Components Ltd., Sussex, England) to reduce charging and improve the secondary electron signals for imaging. The micrographs were recorded using photographic techniques.

Effect of Process Parameters
Batch adsorption experiments for adsorption of CIP on AC(PPZS)KOH were conducted using aqueous solutions of CIP. A stock solution of 1000 mg/L was prepared by dissolving appropriate weight of CIP from Amipharama Laboratories Ltd, Sudan. The stock solution was diluted as required to obtain different concentrations of antibiotic solutions. For each run, a definite amount of AC(PPZS)KOH was added to 25 ml of CIP solution taken in 100 ml Erlenmeyer flasks. All the adsorption experiments were carried out at constant temperature of 25°C.

Effect of pH
Effect of pH on antibiotic adsorption was monitored over a pH range of 2 to 12, using electronic pH -Meter (3510). In this study, 25 ml of separate solutions 50 mg/L (CIP) was transferred into100 ml conical flasks shaking well for 30 min with 0.1g AC(PPZS)KOH at 25°C. The mixture was filtered and the filtrate analyzed for residual CIP using UV visible Spectrophotometer (Jenway 7305).

Effect of Contact Time
In order to study the effect of contact time on the percent removal of (CIP) from aqueous solution, experiments were carried out at initial concentration of 50 mg/L using (0.1g)AC(PPZS)KOH dose and different contact times from 15 to 150 minutes The mixtures were filtered and residual of (CIP) in filtrate analyzed spectrophotometrically.

Effect of Adsorbent Dosage
To determine the optimum adsorbent dosage, experiments were carried out by adding different weights of AC(PPZS)KOH ranging from (0.025 to 0.2 g) to 20 ml of desired concentration of (CIP) in 50 ml conical flask at pH 8, temperature 25°C and shaken for 30min. Aliquots concentration was analyzed to determine the extent of adsorption of (CIP) at equilibrium.

Effect of Initial Drug Concentration
20 ml solutions of CIP drug with different initial concentrations (50-300 mg/L) were contacted with optimized adsorbent dosage 0.1 g and pH 8. The mixtures were shaken well for 30min at 25°C. The mixtures were filtered and filtrate analyzed for residual drug concentrations.

Equilibrium Adsorption Studies
Batch adsorption experiments were studied by adding 0.1 g of AC(PPZS)KOH in to 100 ml conical flask filled with 20 ml of CIP solution of known initial concentration ranging from 50 to 300 mgl -1 at pH 8. The conical flasks were sealed and shaken well at 25°C for 30 min; the samples were then withdrawn and filtered. The residual CIP concentration at equilibrium was estimated spectrophotometrically and the amount adsorbed, q e (mg/g) was calculated using the following expressions [33,34]: Where q e is the amount of the (CIP) adsorbed by the AC(PPZS)KOH sample in (mg/g), C o and C e are the initial and equilibrium concentrations of (CIP) respectively in (mg/L), V is the volume of the solution treated in (L) and w is the adsorbent mass of AC(PPZS)KOH) in (g).
From the Beer's-Lambert's plot for the Ciprofloxacin Hydrochloride drug previously made, the amount of free drug in solution was determined. From the results, the time to attain equilibrium for adsorbent was determined.
The equilibrium data were recorded for investigations using Freundlich and Langmuir isotherms models [35,36].

Evaluation of the Prepared Activated Carbon Sample
The obtained results from Fourier Transform Infrared Spectrum(IR) and Scanning Electron Microscopy (SEM) were used to evaluate the prepared activated carbon sample as follow:

Fourier Transform Infrared Spectroscopy (FTIR)
The FTIR analysis of prepared AC(PPZS)KOH reveals a simple spectrum, shown on figure 3. The spectrum showed the absorption bands at these regions (2900-3650cm -1 ), (1520-1650 cm -1 ), (1000-1260cm -1 ) and (472-419cm -1 ) The broad peak at around 3438 cm -1 is assigned to presence of OH groups (adsorbed moisture) on surface. The sample showed a broad band with a maxima at 2900cm -1 which is attributed to C-H interaction with the surface of the carbon. The presence of amine groups are confirmed by the peaks observed at 1612 and 1575 cm -1 while the band at 1158 cm -1 is due to the C -N stretching. The sharp absorption band at 1125 cm -1 is ascribed for C-O stretching in alcohol, ether or hydroxyl groups.

Scanning Electron Microscope (SEM)
The prepared activated carbon AC(PTLS)ZnCl 2 was examined by Scanning Electron Microscope (SEM) to analyze the surface of the adsorbents. SEM micrograph of the chemically activated carbon by KOH, was presented in Figure 4. Well-developed porous surface was observed at higher magnification. The pores observed from SEM imageis having diameter in micrometer (µm) range. These pores are considered as channels to the microporous network. From the figure, it can be observed that, the adsorbent have rough texture with heterogeneous surface and a variety of randomly distributed pore size.

Effect of pH
Solution pH is one of the important process parameters that significantly influences the adsorption of CIP on adsorbent [33,34]. The adsorption of CIP from 50 mg/L concentration on given AC(PPZS)KOH was studied at pH ranging (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). The result in Figure 5, shows that the adsorption of CIP increased from the initial pH to 8and then decreased over the pH rang of 9-12. Therefore, in this study we found that pH 8 as the optimum pH. At low pH region the surface of the adsorbent will be largely protonated. The positive ions (H + ) provide an electrostatic attraction between the AC(PPZS)KOH surface and the drug molecules leading to maximum adsorption, 86.4% ± 5.7. On the other hand, at pH above 8 the degree of protonation of the surface of the AC(PPZS)KOH will be less, which result in the decrease in diffusion and adsorption, thereby due to electrostatic repulsion. Furthermore, lower adsorption of the Drug molecules in alkaline medium can be attributed to the competition from excess Hydroxide ions (OH‾) with the drug molecules for the adsorption sites.

Effect of Adsorbent Dose
The effect of adsorbent dose on removal percentage of CIP using AC(PPZS)KOH was illustrated in Figure 6. Different doses of adsorbents ranging from 0.025 -0.200 g were considered and other process parameters were maintained constant (pH -8, CIP concentration -50.0 mg/L, Agitation speed -100 rpm, contact time -30 min, and temperature -25°C).
An increase in adsorption capacity with increasing adsorbent dose up to a maximum of 0.05g giving the corresponding optimum removal percentage of89.68%. On the other hand, it is found that any further addition over the above mentioned weight (0.05g) will not make any enhancement in the adsorption process, where almost negligible increase of removal efficiency over the specific adsorbent dose. The initial increase in adsorption capacity with increasing adsorbent mass is explained by the increase in the number of exchangeable sites for CIP adsorption, after which equilibration was attained [16-19, 32, 34].

Effect of Contact Time
The effect of contact time on the removal of CIP is shown in Figure 7. The amount of the adsorbed drug increases with increasing time until it levels off after some 30 min. A constant adsorption is indicative of equilibration due to saturation of adsorption sites. Rapid adsorption of CIP drug during the initial stages was due to the large initial concentration gradient between the adsorbate in solution and the number of available vacant sites on AC(PPZS)KOH adsorbent surface [16-22, 32, 34].

Effect of Initial Ciprofloxacin Concentration
The initial concentration of CIP in the solution is an important parameter since its concentration change over a broad range in effluents applications.
The batch adsorption experiments were carried out with different initial concentrations (C i ) (50, 100,150, 200, 250 and 300 mg/L). The variation of percentage removal the drug with different initial concentration for the prepared activated carbon AC(PPZS)KOH was clarified in Figure 8. The figure shows a excellent performance of the prepared activated carbon at equilibrium state and clarify the optimum drug initial concentration used at confined experimental conditions.

Adsorption Isotherms
The successful representation of the dynamic adsorptive separation of solute from solution by an adsorbent depends upon a good description of the equilibrium between the two phases. Adsorption equilibrium is established when the amount of solute being adsorbed onto the adsorbent is equal to the amount being desorbed [15][16][17][18][19][20][21][22][23][24][25][26][27]. The equilibrium adsorption isotherms were depicted by plotting solid phase concentration (q e ) against liquid phase concentration (C e ) of solute.
Adsorption isotherm explains the interaction between adsorbate and adsorbent and is critical for design of adsorption process. The Freundlich and Langmuir isotherms are the most frequently used models to describe the experimental data of adsorption. In the present work these two isotherms were applied to investigate the adsorption process of CIP on prepared AC(PPZ)KOH at different conditions of process parameters.

Freundlich Isotherm Model
Freundlich isotherm is derived to a model of the multilayer adsorption and for the adsorption on heterogeneous surfaces, the linearized form of Freundlich equation is given by (15-18, 35, 36): ln q e = ln k F + (1/n)ln C e (3) where k F and n are Freundlich constants, q e is the extent of CIP adsorbed per unit mass of adsorbent (mg/g) and C e is the equilibrium concentration of CIP (mg/L). Aplot of log q e against log C e would give the values of n and k F from the slope and it ercept respectively. The slope of 1/n ranging between 0 and 1 is a measure of adsorption intensity or surface heterogeneity, becoming more heterogeneous as its value gets closer to zero, while k F represents the quantity of adsorbate on to the adsorbent. The values of Freundlich constants with the correlation coefficients are shown in Table  1 and Figure 9. The results show a better fit of experimental data of CIP uptake by AC(PPZS)KOH waste, high agreement with Freundlich, and poor less fitting with Langmuir.

Langmuir Isotherm Model
To understand the adsorption isotherm, the Langmuir equation is perhaps the most widely used model due to its simplicity and Strong theoretical reasoning behind. This model suggests monolayer sorption on a homogeneous surface without interaction between sorbed molecules. In addition the model assumes uniform energies of sorption on to the surface and no transmigration of the sorbate. The linearized form of the Langmuir isotherm equation is represented as [15][16][17][18][19][20][21][22][23][24][25][26][27][28]35]: C e /q e = 1/K L q m + C e /q m (4) Where q e (mg/g) is the amount adsorbed per unit mass of adsorbent corresponding to complete coverage of sites, C e (mg/L) is the equilibrium concentration of CIP in solution, q m (mg/g) is the monolayer adsorption capacity of the adsorbent and K L (L/mg) is the adsorption energy. The related parameters are summarized in Table 1, and the linearized Langmuir equation is shown in Figure 10. The results reveal the Langmuir model is not able to describe the experimental data properly, poorless fitting on AC(PPZS)KOH.

Conclusion
The adsorption of Ciprofloxacin hydrochloride (CIP) onto Activated Carbon derived from Pomegranate Peel wastes collected from Alziedab Agricultural Scheme at River Nile state, Sudan has been studied. Adsorption experiments were tested at various parameters such as sorbent dosage, contact time, pH, and CIP concentration. The equilibrium data were analyzed using Freundlich and Langmuir, isotherm models and the results are well fitted to Freundlich equations. It was found that the equilibrium was reached within 30 min; also it was found that the optimum pH value of the CIP adsorption was 8. The present work concludes that AC(PPZS)KOH agricultural wastes is effective adsorbent in removing CIP from aqueous solutions. The optimum conditions which have been obtained in adsorption process for treating the aqueous phase were 50 mg/L for initial CIP concentration, 8 pH for solution alkalinity, and 2.50g/L for mass of adsorbent. The equilibrium data obtained for the prepared activated carbon, AC(PPZS)KOH, is fitted to the Freundlich model more than the Langmuir. It was observed that the Freundlich adsorption isotherm conforms to the adsorption of CIP from aqueous solutions using AC(PPZS)KOH, the level of conformity is to a high extent compared to the Langmuir adsorption isotherms as indicated by higher correlation coefficient values of 0.991.