Research On Yemeni And Huludao Zeolite As Adsorbent Material For NH₄⁺ And PO₄^3-

The functionalization of industrial minerals with high commercial properties, such as natural Zeolites is shaping as a promising approach in environmental sphere.In fact, under the specific conditions, the surface functionalization by adsorption of cationic surfactants reverses the surface charge of the mineral, enabling Zeolites to simultaneously interact either with organic contaminants or inorganic anions.This aspect allows Zeolites to be used in the remediation of contaminated fluids.Phosphate and ammonium ions are major components of most fertilizers and detergents.More often than not, these chemicals find their way into water bodies either through run-off or direct discharge from industries.When the concentration exceeds the maximum tolerable limit required by the aquatic environment, eutrophication results, there by threatening the ecosystem.This is as a result of the explosion of algal population due to increase in nutrients （NH4+ and PO43-）which then deplete other aquatic organism of oxygen supply and sometimes also releases toxin into the environment. A cheaper and efficient material for adsorption and ion exchange of these pollutants has become the focus of most research endeavors.Interest for natural Zeolite-bearing materials has been heightened due to the increasing demand for low-cost, ion exchange and adsorbent. In addition,despite the large number of different studies on the removal of contaminants ions from aqueous solutions using Zeolite, every special Zeolite requires individual research.This study was conducted in disclosing characterization of Clinoptilolite, a kind of Yemeni natural Zeolite to evaluate its potential as an adsorbent material.As well as, an investigation into the optimum modification conditions for contaminants removal was established and the result was compared with the removal efficiency Chinese zeolite.This research also reports the efficiency of Yemeni（Al-Ahyuq） natural Zeolite on removal of ammonium and phosphate as single and binary components.Furthermore,influence of various variables including solution’s pH, mass of Zeolite,contaminants concentration, adsorption time, and temperature of water on removal of ammonium and phosphate was evaluated.The present dissertation is comprised of two parts:A-The first part comprises of field investigation and laboratory testing of Zeolitic tuffs.The present work describes the mineralogical,chemical composition and morphology of a natural Yemeni （Al-Ahyuq） Zeolite and its potential as an adsorbent material.The Zeolite deposits of Al-Ahyuq area, in Taiz Province,Yemen were formed by alteration of volcanic tuffs （Yemen Trap Series）.A total 40 Zeolite samples of Al-Ahyuq area about 0.5kg each were selected and examined to determine their mineralogical and chemical composition. Mineral identification, chemical analysis and morphological insights of Zeolite samples were conducted using X-ray Diffraction （XRD）, X-Ray Fluorescence （XRF） and Scanning Electron Microscopy （SEM）, respectively. XRD data showed that the Zeolite minerals purities range from78 to100% Zeolite.The results also indicated that Clinoptilolite and Mordenite the major mineral present in the deposit whereas Heulandite and Stilbite occurs in minor amounts. Accessory minerals include quartz, illite, Mica, Feldspar, Kaolinite, and Semectite.Chemically, the Zeolite tuff in Al-Ahyuq area ranges were 61.01-72.00%SiO2,10.96-14.41%Al₂O₃,1.12-7,41%K₂O,0.74-3.68%Fe₂O₃, 0.47-3,53%CaO and 0.47-3.53%Na₂O.These results show that the chemical compositions of AI-Ahyuq Zeolitic tuffs are found to be comparable with other Zeolites compositions of high economic value in the world.On the basis of bulk mineralogical, chemical composition and ion cation exchange, natural Zeolite of Al-Ahyuq area display a potential for environmental applications.B-Consider the removal of ammonium and phosphate as single and binary components from aqueous solution, presented in three separate sections:The first section present the first attempt to investigate the effectiveness of Al-Ahyuq natural Zeolite on the removal of ammonium ion （NH4+） and subsequent comparison with Chinese （Huludao） Zeolite. The development of the process of sodium activation of Zeolite has been an effective technique for enhancing the efficiency of ammonium removal.The optimum conditions for the activation of Al-Ahyuq and Huludao Zeolite of the most effective parameters such as sodium concentration, stirring time, and temperature were determined. The most efficient conditions were selected according to the highest ammonium removal capacity. The kinetics and isotherms of ion exchange were studied in a batch system. Important parameters which affect the ion exchange, such as pH of the solution, temperature, contact time, Zeolite mass and initial ammonium concentration were investigated.The characteristics of natural, modified Zeolite and their mechanism of ammonium removal was investigated and compared with Huludao Zeolite. Both Zeolites were fully characterized by scanning electron microscopy （SEM）, Energy-dispersive X-ray spectroscopy （EDS） technique, zeta potential （Z-potential）, X-ray diffraction （XRD）, X-Ray Fluorescence（XRF）,Fourier transform infrared spectroscopy（FTIR）, thermogravimetry analyzes（TGA） and specific surface area（SSA） analysis.The results demonstrate that the mechanism of NH4+ removal on Zeolite was Na+ion exchange and had maximum removal efficiency of about 99% based on the relevant parameters.The highest ion exchange capacity for Al-Ahyuq Zeolite was obtained at 35℃ whereas, for Huludao Zeolite it was attained at 25℃. Moreover, the kinetic data for both Zeolites followed closely the pseudo-second order model while ion exchange isotherm results illustrated that Langmuir model（LM） provided the best fit for the equilibrium data. In addition, thermodynamic parameters such as change in free energy（△G°）,enthalpy（△H°） and entropy（△S°）were also calculated.The parameters revealed that the exchange process of ammonium ion by both Zeolites is spontaneous and exothermic. As indicated by values of △G°, the selectively for NH4+ions by both Zeolites suggested an order of preference:Al-Ahyuq activated Clinoptilolite> Huludao activated Clinoptilolite> Al-Ahyuq natural Clinoptilolite> Huludao natural Clinoptilolite. The results demonstrated that the Si/Al molar ratio of Zeolites determined the selectivity for NH4+.The second section aims at developing and evaluating an effective technique for the enhanced removal of phosphate ion （PO43-） by a novel composition of TiO2/Al-Ahyuq Zeolite adsorbent. The characteristics of TiO2/Zeolite （TZ） and its mechanism for PO43-removal were investigated and compared to that of natural Zeolite （NZ）. In addition, both Zeolites were fully characterized with a variety of techniques. Important parameters which affect adsorption were investigated as in the first section. The TiO2/Zeolite composite revealed the highest phosphate removal efficiency approached 100% at low initial PO43-concentrations.The specific surface area and PO43- adsorption capacity of the composite material reached 166.5 m2/g and 37.6 mg/g, respectively. Moreover, Maximum adsorption for both Zeolites occurred at 2 to 4 pH and 35℃.The results of zeta potential, FTIR,XRF and EDS analyses indicated that electrostatic attraction and replacement of surface hydroxyl groups （T\OH） by phosphate were the main adsorption mechanism. The adsorption isotherm results illustrated that Freundlich model（FM） provided the best fit for the equilibrium data.Furthermore, thermodynamic parameters such as change in free energy（△G°）, enthalpy（△H°） and entropy（△S°） were also calculated. The parameters revealed that the adsorption of PO43- ion by Zeolite is spontaneous and endothermic in nature. It was concluded that a Ti02/Zeolite composite is a highly efficient and economic adsorption material with good regeneration and can be utilized in the remediation of environmental pollution.The third section explore the feasibility of the simultaneous removal of phosphate （PO43-） and ammonium （NH4+） from simulated reclaimed waters by employing NaCl,AlCl3 and thermally modified Al-Ahyuq Zeolite. The characteristics of Al-modified Zeolite （AlZ） and its mechanism for PO43- and NH4+ removal were investigated and compared to that of natural Zeolite.The surface area of AlZ and the content of Na and Al increased whereas the Ca,K and Mg content decreased after Zeolite modification. Yemeni natural Zeolite （NZ） under the modified condition of 1M NaCl and 10 ml/g of pillaring dosage, the ammonium and phosphate removal efficiencies of AlZ from simulated reclaimed water reached 97.80% and 98.60%, respectively. The results of FTIR, XRF, BET and EDS analyses indicated that replacement of the surface hydroxyl groups （Al\OH） was the main adsorption mechanism for phosphate while the Na+ ion exchange was the main mechanism for ammonium removal.In addition, the kinetic experiments showed that the adsorption of ammonium and phosphate followed pseudo-second-order model whereas the adsorption isotherm of ammonium and phosphate is more consistent with the Langmuir isotherm model （LM）. Moreover, the change in free energy（△G°）, enthalpy（△H°） and entropy（△S°） revealed that the adsorption of NH4+and PO43- ion by AlZ is nonspontaneous and endothermic.It was concluded that NaCl, AICI3 and thermal modification of Al-Ahyuq Zeolite can significantly improve the simultaneous removal of NH4+ and PO43- at low concentrations from aqueous solutions.Finally,this dissertation concluded that Al-Ahyuq and Huludao Zeolites can be used as a substitute for the more expensive adsorbents because it is a readily available, cheap, regenerable and ecofriendly adsorbent suitable for removing of ammonium and phosphate a single or binary components from wastewaters.However,Al-Ahyuq Zeolite is a more cost effective adsorbent than Huludao Zeolite because the high quartz content of Huludao Zeolite necessitates additional purification step thus adding to overall cost.