Theses supervised by Mustafa Gazi
13 theses · Eastern Mediterranean University
The Preparation and Characterization of Phosphoric Acid modified Ferula Communis Biomass and its Application in the Removal of BR-9 Dye
In this study, the potential of Ferula Communis biomass (FC) was evaluated for removal of cationic dye from aqueous solution. Phosphoric acid modified FC was utilized to remove basic red 9 (BR-9) under varying adsorption parameters such as pH, temperature, contact time, adsorbent dosage, and ionic strength. The adsorption process using modified FC (PFC) was evaluated under isothermal conditions and Langmuir model showed monolayer adsorption of 354.89mg/g with high R2 value of 0.9997 compared to Freundlich model. The adsorption process was evaluated under various kinetic models. The experimental results indicated that BR-9 removal fit well with pseudo-second order kinetic and the treatment process is exothermic and spontaneous in nature. The obtained results showed that PFC can be used as an alternative adsorbent for the treatment of dye-containing wastewaters. Keywords: Ferulla Communis, Basic Red 9 (BR9), Biomass, Dye Removal, Adsorption, Water Treatment.
Boron-doped Sucrose Carbons for Supercapacitor Electrode: Artificial Neural Network-Based Modelling Approach
Here, a simple yet efficient and economic strategy was demonstrated for the production of multiporous boric acid-doped sucrose carbon (Bx–pC) for supercapacitor application. The electrochemical performance was established through cyclic voltammetry and galvanostatic charge/discharge tests. Bx–pC samples were characterized by X-ray diffraction, scanning electron microscope, Raman spectroscopy and nitrogen adsorption/desorption at − 196 °C. The results reveal that the optimum boron dopant is 2 wt.%; and B2–pC containing 2 wt.% boron exhibited honeycomb-like porous structure (2.88 nm) and a high specific surface area of 1298.9 m2g –1 . The B2–pC based symmetric supercapacitor delivered a remarkable energy density of ~56 Wh kg−1 , a high power density of 1300 W kg−1 and superior capacitance of 239 F g−1 at 1 A g−1 in 1 M H2SO4 electrolyte. To establish the complex relationships between the electrode structure, active operating conditions and electrochemical performance of the supercapacitor, an artificial neural network (ANN) methodology was utilized herein. After several random runs, the ANN maintained satisfactory predictive performance with an average error rate of ~1.06% and desirability function of 0.93 which is closer to 1.0. Keywords: supercapacitor performance; sucrose-based porous carbons; artificial neural network optimization; electrochemical analysis.
Synthesis and Characterization of Polysaccharide Based Hydrogels for removal of Mercury Ion from Aqueous Solution
Production of major industrial products may degrade the environment. It can result in water pollution since it produces pollutants such as water-coloring agents and toxic heavy metals that are extremely harmful and impair the environment even at low concentrations. To reduce the risk of environmental pollution from these wastes, it is necessary to treat them prior to discharging into the environment. The adsorption process onto solid substrate and natural polymeric materials especially polysaccharides is considered superior to other removal techniques. Mercury deserves special attention among heavy metals such as cadmium, cobalt, chromium, copper, lead, nickel, and zinc, which are highly toxic and dangerous. Mercury spillage is highly dangerous because it destroys brain tissue, lungs, and has the ability to distort protein leading to toxic effects; it mainly affects the kidney and nerve system and may cause some disorders and diseases. Therefore, the removal of mercury from aqueous solutions, especially drinking water, is very important in hydrometallurgical and wastewater treatment. The main aim of this thesis is to investigate the mercury ion removal ability of different natural polymers, cellulose, chitosan, and pullulan. For this purpose, acrylamide monomer has been grafted to chitosan, cellulose, and pullulan and three different hydrogels were synthesized. In addition, the cellulosegraft-polyacrylamide/nano-hydroxyapatite composite hydrogel and pullulan-graftpolyacrylamide porous hydrogels were prepared and characterized using FTIR and SEM. Then, the effects of several variables such as time, temperature, and pH on the swelling behavior of the hydrogels were examined. The results showed that the cellulose-graft-polyacrylamide hydrogel with 5170 % has the maximum and pullulan-graft-polyacrylamide hydrogel with 1554 % has the minimum swelling amount. In addition, the swelling amount of all hydrogels significantly changed with temperature and pH and the kinetics of swelling of hydrogels were best fitted with the second-order model. Finally, the adsorption studies of the mercury (II) ions on synthesized hydrogels were performed to investigate their uptake performances. The results showed that the maximum mercury ion adsorption by cellulose-graft-polyacrylamide hydrogel (1.93 g.g -1 ), cellulose-graft-polyacrylamide/hydroxyapatite composite hydrogel (1.99 g.g1 ), chitosan-graft-polyacrylamide hydrogel (1.87 g.g-1 ), pullulan-graftpolyacrylamide hydrogel (1.75 g.g-1 ), and pullulan-graft-polyacrylamide porous hydrogel (1.78 g.g-1 ) were attained after 24 h. In addition, batch adsorption experiments in different conditions such as temperature, pH, mercury solution concentration, with different amount of adsorbent were performed. According to the results, all synthesized hydrogels are temperature, pH and concentration sensitive. In addition, the kinetic, isotherm, and the thermodynamic parameters of adsorption were calculated. The results indicated that adsorption of mercury ions on all hydrogels followed pseudo-second-order kinetics and best fitted with Langmuir adsorption isotherm with the highest maximum adsorption (qmax) of Hg(II) ions for composite hydrogel and the lowest for pullulan based hydrogels. The negative value of free energy change (ΔGº) and positive value of enthalpy change (ΔHº) shows the adsorption process is spontaneous and endothermic. Finally, the regeneration ability of hydrogels through desorption of mercury ions for three adsorption/desorption cycles were examined. It can be concluded that the synthesized hydrogels qualified for practical application since they can be used repeatedly with negligible loss of adsorption capacity for the mercury ions. Keyword: Cellulose, chitosan, pullulan, hydroxyapatite, hydrogel, porous hydrogel, composite hydrogels, water treatment, mercury
Adsorption of Methylene Blue from Solution Using Anionic Surfactant Modified Palm Seed Powder
Cationic dyes are widely utilized in plastic, textile, leather and tanning industries. High concentrations of these dyes in aquatic environments pose serious threat to human health and the environment due to their toxic profile. Therefore, various environmental protection agencies and governments have established standard control limits to the quality of domestic and industrial effluents before being discharged to water bodies. Among the various treatment processes, adsorption technique was employed in this study for the treatment of methylene blue (MB) simulated effluents under various operational conditions. Here, palm seed powder (PS) was employed as adsorbent for removal of MB from laboratory simulated colored effluent. The sorption capacity of the PS was improved through surface modification by anionic surfactant (sodium dodecyl sulfate). Comparatively, the modified palm seed powder (MPS) efficiently removed 93% of MB while only 57% removal was recorded by PS after 720 min treatment time. The MPS sorption capacity was affected by the presence of interfering ions (Na+ and Mg2+); however, about 18 mg/g of MB was removed even at salt concentration of 100 mg/L. Freundlich isotherm fits suitably the MPS experimental data more than Langmuir isotherm, indicating multilayer sorption process of MB on the heterogeneous MPS surface. The Weber–Morris models confirmed that intraparticle transport played a significant role in the sorption process. Keywords: Adsorption; modified palm seed powder, cationic dyes removal
Azo-Dye Eriochrome Black T Degradation by Heterogeneous Fenton-Like Reaction Using Olive Stones Activated Carbon-Fe Catalyst
Chemically activated carbon K-AC was fabricated from a by-product of olive oil production (olive stones) after chemical treatment with KOH. The as-synthesized activated carbon was then used for; (1) adsorption of an azo dye, Eriochrome black T (EBT) and (2) to prepare a heterogeneous Fenton catalyst Fe-AC, for degradation of same dye using the Fenton-like process. Evaluation of the effect of pH (2-10), temperature (20-50 °C) and contact time required for adsorption was studied while effects of hydrogen peroxide concentration, EBT concentration and time on rate of degradation of EBT was also determined. Optimum conditions for both processes are reported while kinetics of EBT adsorption and degradation was also investigated. Results from the undertaken study showed that temperature and pH had a predominant impact on the adsorption of EBT by K-AC. Also, the Langmuir isotherm equation provided a better fit to experimental data than Freundlich equation implying monolayer adsorption on surface of K-AC. Maximum adsorption capacity of K-AC at 20 °C as determined using the Langmuir isotherm was 101.01 mg/g. RL (0.54-0.92) and n (1.04) values confirmed that the adsorption process is favorable while positive enthalpy (ΔH°; 32.7 KJmol-1) and negative free energy (ΔG°; -1.07 KJmol-1) referred to an endothermic and a spontaneous adsorption process. EBT degradation increased as time and peroxide concentration increased. However, it decreased as EBT concentration increased. Overall, degradation experiments were conducted at optimum conditions (6mM H2O2 and pH 4) to evaluate catalyst degradation efficiency. It was further observed that adsorption kinetics of EBT followed pseudo second order kinetic model based on R2 values. Further analysis on the regeneration of spent Fe-AC using water indicates that catalyst degradation efficiency can be maintained even after three cycles which makes it economical to use in EBT degradation. According to results obtained in this study, both K-AC and Fe-AC can act as adsorbent and catalyst for the efficient removal of EBT dye. Keywords: Olive stones, Fenton process, Adsorption, Eriochrome black T
Bio-derived CuO/olive Cake Nanocomposite for Total Phenols Removal from Olive-mill Wastewater
Acutely high organic-loaded olive mill wastewater (OWW) is produced seasonally from the olive oil processing sectors. In North Cyprus, there is no regulated policy regarding the discharge of olive mill wastewater. Hence, the OWW is routinely discharged into the environment top soil or evaporation ponds, and the solid wastes disposed of without treatment to surrounding lands near the processing mills. This poor management of OWW enhances the risk of polluting the surface water and agricultural soil resources. The environmental threat of the olive mill wastewater is majorly due to the toxicity and low biodegradation of phenolic compounds present in the OWW. This research focused on the feasibility of integrating bio-derived nanoparticles into the surface of waste olives cakes and converting into a high-performance and environmentally nanocomposite adsorbent for removal of total phenol from OWW. An efficient bio-derived CuO/olive cake nanocomposite (BCO-NC) with 266.11 m2/g surface area was prepared using banana peel extract. Under optimised conditions (pH 6 and dosage 2.5g), 80% of total phenols was removed after 180 min in the dark (BCO–NC/dark), but rapidly increased to 100% just after 90 min using BCO–NC/H2O2/sunlight system at pH 10, dosage 1.0g and H2O2 1mM. The removal mechanism is represented by Freundlich isotherm model (R2= 0.996–1.00) and best modelled by pseudo-second-order kinetic. Keywords: Bio-derived nanocomposite; olive mill wastewater, total phenols removal
Adsorptive Removal of Nickel from Aqueous Solution by Palm Seeds-based Magnetic Biochar
Here, the possibility of using biomass wastes such as palm seed as a suitable precursor for the preparation of magnetically responsive adsorbent was explored. Magnetic biochars (MB) were prepared from raw palm seed in the presence of iron oxide (Fe3O4) particles and utilized for adsorption of nickel. The thermal decomposition processes of the adsorbents were determined by thermogravimetric analysis. The physical structure and textural characteristics of the adsorbents were investigated. The effects of adsorption parameters, including pH, adsorbent dosage, temperature, interfering ions and contact time were investigated. The results showed that the magnetic biochar exhibited high sorption capacity, excellent dispersion and convenient separation after spent. The relationship between the MB and the pollutant (Ni2+) was established to follow Langmuir model, described well by pseudo-second-order kinetic and intraparticle diffusion played an important role in the sorption process. 27.8 mg/g was obtained as the maximum nickel uptake. The values of thermodynamic parameters revealed that the sorption process depended on the temperature of the medium, was spontaneous and endothermic in nature. Lastly, the magnetic biochar was regenerated via a simple technique and reuse with no significant loss in activity, suggesting that MB is technically and economically efficient. Keywords: Magnetic biochar, palm seed powder; nickel (II) ions, adsorption
Anti-Bacterial Properties of Boron Cross-linked Chitosan/Poly (Vinyl Alcohol) Hydrogels Containing Zinc Oxide Nanoparticles
Chitosan is a hydrophilic and versatile polysaccharide possessing functional groups such as carbonyl and amine groups which are areas for antimicrobial activity. PVA has high degree of swelling in aqueous solutions and mostly blended with chitosan because of its good tensile strength and elastic nature. Six chitosan- PVA hydrogel samples were prepared by varying the amounts of chitosan and PVA, blending them with equal amounts of boric acid ( cross-linker), soaking them in sodium hydroxide overnight, washed several times with distilled water, freeze- thawed at -200 for 6hrs and + 370 for 2hrs respectively for 5 cycles, then dried in an oven and later analyzed. During the hydrogel preparations, the first three samples were blended without zinc oxide nanoparticles and the last three with equal amounts of zinc oxide nanoparticles. Swelling percentages of samples 1- 3 were evaluated in 2 ways: (1) soaking a known amount of each dried sample in distilled water while varying time. (2) soaking another known amount of dried samples in different pH buffer solutions for 24hrs. Its kinetics showed that: as the pH increases, their swelling % increases and starts dropping as the pH gets more basic and that the higher the amount of PVA in a sample, the higher its swelling % in water with increased time. The bacterial analysis of the samples were carried out in order to determine the effect of an increased amount of chitosan and of zinc oxide nanoparticles on bacterial growth. The LB agar medium was used for the culturing of the E.coli bacteria which is a gram negative bacteria possessing a thinner peptidoglycan membrane. The sample with the highest amount of Chitosan showed more inhibition than the others and the addition of nanoparticles to this sample showed an even more greater inhibition towards the bacteria. Finally the Scanning electron microscopy (SEM) and FTIR of the prepared hydrogels were done inorder to determine the surface structures of the hydrogels and the various functional groups present in each hydrogel respectively. Keywords : Chitosan-PVA hydrogel, Zinc oxide nanoparticles, Boric acid cross linker, Antibacterial properties, Swelling properties.
Removal of Safranin Dye from Aqueous Solution using Surfactant-Modified Carbonized Olive Stones
The adsorption study of safranin dye by surfactant modified carbon MCOS produced from olive stone under batch adsorption process was undertaken to check the influence of varying different experimental conditions; initial safranin concentration, pH, adsorbent dosage, temperature, counter ions and time on safranin removal by our adsorbent. Physiochemical characterizations including moisture content, ash content, bulk density etc. was also undertaken. Two well known adsorption isotherms (Langmuir and Freundlich) and three kinetic models (pseudo first and second order, intra particle diffusion) were used to better understand the mechanism involved in the adsorption process. Our collected results showed that there was an increase in adsorption capacity of MCOS as initial dye concentration, dose and number of counter ions in solution increased; pHpzc was at pH 6.6 while maximum adsorption capacity was 7.30mg/g obtained at pH 7. Langmuir isotherm which implies monolayer coverage by MCOS well represented our equilibrium data with a higher correlation coefficient value of while kinetic study showed that adsorption process followed pseudo second order kinetic model. RL and n values obtained from both adsorption isotherms used indicates a favorable adsorption process. The spontaneity and exothermic nature was confirmed by negative ΔG° and ΔH° values, though spontaneity reduced as temperature increased. Hence, MCOS can serve as an ecofriendly and cheap alternative for removing safranin from industrial waste effluents.
Preparation, Characterization and Dye/Heavy Metal Adsorption Properties of Bio-based Composites
Biomagnetic composite based on raw Ferula communis and polyacrylamide (MBFC) was synthesized. The MBFC proved to be an effective and high performance adsorbent for the removal of heavy metals, acidic and basic dyes from simulated effluents by batch and fixed-bed experiments. The morphology, surface and magnetic properties of the as-prepared MBFC were examined by Boehm titration; scanning electron microscope and Fourier transform infrared techniques. The sorption process was optimized via Box-Behnken approach and techno-economic analysis completed using central composite design. The adsorption isotherm, kinetics and parametric behaviors of the pollutants were investigated, and detailed explanation of the results is discussed. The maximum removal efficiencies of the pollutants of 69.3─96.9% were obtained at the optimum operation conditions of 50 mgL─1 initial adsorbate concentration, 100 mg MBFC dose, 360 min contact time, pH 4.0 (acidic dyes) and pH 7.0 (basic dyes and heavy metal ions). The rate-controlling mechanism is discussed in terms of intraparticle diffusion, and the actual step was confirmed by Boyd model. Finally, the efficiency and stability of MBFC were assessed via several regeneration-reuse cycles. Keywords: Bio-based composite; acid dyes; basic dyes; heavy metals; adsorption optimization; modeling; thermokinetic studies.
Glucose Responsive Hydrogels: Synthesis and Investigation of the Biomedical Applications
The growing rate of diabetes mellitus (DM) has called for urgent concern among researchers and expert in the field of drug delivery. Hence, the present work synthesized pH and glucose-sensitive hydrogels with promising antibacterial applications. The hydrogel (CS─PVA) was synthesized via boric acid crosslinking and freeze-thawing cycle techniques. The surface chemistry of CS─PVA hydrogel was confirmed by scanning electron microscopy and Fourier transform infrared spectroscopy. The hydrogel displayed high glucose-sensitivity under physiological conditions, and its sensitivity was noticed to increase in the presence of varied glucose concentrations. Additionally, the swelling and drug loading behavior of the hydrogel was influenced by the pH of the medium. Under optimized conditions, the cumulative drug releases ranged between 33─86% for bovine serum albumin and 39─92% for insulin at 37°C in PBS solutions and in the presence of glucose. The synthesized hydrogel exhibited excellent antibacterial activity and was found to reduce the growth of E.coli (gram negative) bacterial by 86.5%. Keywords: Chitosan; glucose sensitivity; drug delivery; antibacterial; hydrogels; swelling; optimization.
Bio-based Adsorbent for Removal of Safranin Dye from Aqueous Solutions
The potential of dried (CC) and anionic surfactant modified (MCC) prickly pear cactus cladodes as an ecofriendly and low cost material for safranin removal from simulated wastewater was evaluated. Effect of several operational parameters including; pH of safranin solution, counter ions, dosage etc. on the adsorption capacity and removal efficiency of safranin was investigated. Physiochemical characterization of the adsorbents was also undertaken. The experimental data obtained was then tested using different mathematical adsorption isotherms and kinetics. Results obtained in this study found that the modified cactus samples MCC performed better than the unmodified one CC in all experiments conducted. The adsorption capacity of both samples towards safranin decreased with increasing concentration of competing ions, ionic strength and dosage. Kinetic studies followed the pseudo second order kinetic model; intraparticle diffusion was involved but wasn’t the rate determining step while equilibrium process was well represented by the Freundlich model for MCC. Positive ΔH° (30.4 and 9.2 KJ/mol) and ΔS° (109.7 and 47.6 J/mol K) values coupled with negative ΔG° for both CC and MCC determined from the thermodynamic study confirmed the process to be a spontaneous, endothermic and random disorderly process. Generally, adsorption of safranin by CC and MCC proved to be effective and suggests that they can be used as an alternative adsorbent for wastewater rich in safranin.
Chitosan-graft-Poly(trichlorovinylsilane) Polymers: Synthesis, Characterization, Antibacterial Susceptibility and Dye Adsorption Studies
In this study, chitosan-grafted-trichlorovinylsilane (CT–g–VTCS) film is produced and elucidated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The SEM micrograph of exhibited refine structure with rough surface. The CT–g– VTCS antibacterial action was assayed using the agar diffusion and broth dilution approach. Obtained results herein pointed out that CT–g–VTCS exhibited increased water solubility (67 mg/mL) when compared with chitosan (CT) film (2.6 mg/mL). CT–g–VTCS exhibited improved antibacterial action against S. aureus, E. coli, Kleb spp., E. faecalis and Methicillin-resistant Staphylococcus aureus (MRSA) (minimum inhibitory concentration (MIC) = 0.078 – 0.156 mg/mL and minimum bactericidal concentration (MBC) = 12.5 – 3.12 mg/mL) higher than the precursor CT film. Contrary to most quaternized chitosan derivatives, the CT–g–VTCS was processed via a simple and easy route and showed comparatively high antibacterial efficiency. Studies from the time-kill assessment revealed that 5 mg/mL CT–g–VTCS exposed to the bacteria cells is copious to give a ~0.08 log10 reduction (>99.9% kill rate) within 24 h. Vinyltrichlorosilanechitosan-graft-polyacrylamide (VCSCT-g-PAAm) hydrogel was also synthesized. From the results obtained, hydrogels with varying molar ratios of VCSCT-g-PAAm all formed within 13 min. The incorporation of polyacrylamide onto vinyltricholosilane–chitosan backbone enhanced the hydrogel physical and chemical properties in terms of strength, swelling capacity, adsorptivity and antimicrobial activity. The VCSCT-g-PAAm hydrogel interacted with methylene blue (MB) dye solution at different mass-liquid ratio, pH and temperature. The amount of MB dye removal was estimated using UV-Vis spectrophotometer at an optical density of λmax= 665nm. The MB dye removal was most effective at pH 12 with about 98% removal at 50oC. The hydrogel was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and other physicochemical parameters. Experimental data obtained for the adsorbent-MB dye pair suited the Langmuir, Freundlich and pH-dependent Langmiur Freundlich adsorption isotherms. Calculated values for ∆Ho , ∆So , ∆Go were - 2.72kJ/mol, 16.72J/mol K and 7.73kJ/mol correspondingly. Further studies revealed high swelling ratio in basic solution with about 1,179% swellability. Investigations showed that VCSCT-g-PAAm hydrogel exhibited a high percentage killing against S. aureus and E. coli, more than 99.9% kill rate after 24 hr contact with S.aureus and E.coli, this can contribute immensely in biomedical application and beneficial in waste water treatment. Keywords: Chitosan, Trichlorovinylsilane, Antibacterial, Adsorption, Methylene blue.