Synthesis and characterization of zeolite and its application in adsorption of nickel from aqueous solution

Project Abstract

Zeolites are crystalline aluminosilicate materials with a unique porous structure and high surface area, making them excellent candidates for various applications including adsorption of heavy metals from aqueous solutions. In this study, zeolite was synthesized using a hydrothermal method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherms. The synthesized zeolite exhibited a well-defined crystalline structure with a high surface area and pore volume. The application of the synthesized zeolite in the adsorption of nickel from aqueous solution was investigated. Batch adsorption experiments were conducted to study the effect of various parameters such as initial nickel concentration, contact time, and pH on the adsorption process. The results showed that the zeolite adsorbent had a high affinity for nickel ions, with a maximum adsorption capacity of 45 mg/g at an initial nickel concentration of 100 mg/L. The adsorption kinetics and isotherms were also studied to understand the mechanism of nickel adsorption onto the zeolite surface. The adsorption process followed pseudo-second-order kinetics, indicating a chemisorption mechanism. The equilibrium data were well-described by the Langmuir isotherm model, suggesting monolayer adsorption of nickel ions on the zeolite surface. Furthermore, the effect of pH on the adsorption process was studied, and it was found that the adsorption capacity of the zeolite increased with decreasing pH due to the protonation of surface functional groups. The pHpzc of the zeolite was determined to be 6.5, indicating its cation exchange capacity and surface charge properties. Overall, the synthesized zeolite showed promising results for the adsorption of nickel from aqueous solution, demonstrating its potential for environmental remediation applications. The high adsorption capacity, excellent reusability, and cost-effectiveness of the zeolite make it a viable alternative for the removal of heavy metals from contaminated water sources. Future studies could focus on optimizing the synthesis parameters of zeolite to enhance its adsorption performance and exploring its application in real-world wastewater treatment scenarios.

Project Overview

<p> </p><p>1.0 Introduction<br>Zeolites are porous crystalline alumino-silicates of regular skeleton structures formed<br>by alternating silicon-oxygen and aluminum-oxygen tetrahedrons. Although only natural<br>zeolites were initially used, synthetic zeolites, due to their well-tailored and highlyreproducible<br>structures, have been used extensively as ion exchangers, adsorbents, separation<br>materials and catalyst1.The negative charges in aluminum-oxygen tetrahedron, which are not<br>rigidly fixed to the skeleton of zeolites, are compensated with cations, so they are capable of<br>interchanging. Silicon-oxygen and aluminum-oxygen tetrahedrons in the zeolites of the type<br>A, X and Y form a complex structural unit of cubooctahedron. The combination of such units<br>forms the structure of type A, X and Y [fig 7].. The difference between them consists in the<br>fact that they are interconnected by means of different number of member rings (i.e., eight<br>member rings (A), twelve member rings (X, Y). The chemical difference of zeolite is defined<br>by the ratio of Si/Al. For zeolite A this values is in the range of 0.95-1.051-3. Zeolites A, X<br>and Y are the most important ones to be used in pharmaceutical, petrochemical and detergent<br>industries.<br>Zeolites with different structure are known to be obtained by synthesis 2-7. They are<br>either synthesized from alumino-silicate hydrogel or by conversion of clay minerals. The<br>hydrogel can be prepared from different sources of silica and alumina, but the types of<br>starting materials and the method of mixing determine the structure of the resulting gel.<br>Moreover, the nature of the gel influences the rate of the subsequent crystallization, which<br>affects the particle size distribution, and the formation of impurities8. The general pathway<br>for zeolite synthesis follows a specific temperature gradient at low temperatures (&lt;60 oC)<br>2<br>where the sources of aluminum, silicon and water are placed in solution and mixed until a gel<br>is formed9.<br>Figure 1: Structure of zeolite framework<br>1.1 Background of Study<br>The extremely fast growth of the world population in the last century, in addition to<br>the industrial revolution, reflected in a considerable rise in both fresh water consumption and<br>waste water production. Fresh water demand has already exceeded supply; and currently<br>special treatment is more and more often required in order to obtain drinking water of high<br>quality as well as to produce environmentally acceptable effluents.<br>Species of toxic heavy metals cause serious damage to the ecosystem and as a result<br>of this fact, there is an increase in research on processes for wastewater treatment3. Many of<br>the wastewater treatment processes are based on adsorptive properties or ion exchange of<br>some of these materials which immobilize the heavy metal species. Recently, various<br>materials of natural or synthetic origin, such as bagasse, coal ash, carbonates, phosphates and<br>zeolite have been tested for their sorption capacity.4 Zeolite are commonly used for sorption<br>of heavy metals due to their physical and chemical properties (thermal stability, defined<br>molecular structure and ion exchange capacity.<br>3<br>1.2 Statement of Problem<br>The presence of large quantities of toxic metals such as mercury, lead, cadmium,<br>zinc, nickel and others in water poses serious health risk to humans, and this threat puts the<br>scientific community under pressure to develop new methods of detecting and removing<br>toxic contaminants from wastewater in efficient and economically viable way. The<br>production of zeolite from chemical sources (Al and Si ) are expensive but have the<br>advantage of producing zeolites of high purity with highly engineered chemical and physical<br>properties suitable for some specific applications in pharmacy, electrochemistry,<br>photochemistry, nano technologies, industries as well as for academic research purposes. The<br>greatest challenge now is the need to develop low cost and efficient adsorbents for nickel ion<br>removal from wastewater.<br>1.3 Objectives of the Study<br>The objectives of this study are:<br>i. To synthesize zeolite from analytical grade chemical.<br>ii. To characterize the synthesized zeolite using spectroscopic techniques such as<br>XRD, SEM and AAS.<br>iii. To use the synthesized zeolite to adsorb nickel ion from aqueous solution.<br>iv. To study the effect of pH, temperature, contact time and adsorbent dosage in<br>nickel metal removal.<br>1.4 Justification of the Study<br>The wide range of zeolite applications and the need to synthesize zeolite with high<br>purity motivated this work.The study has proffered cheaper routes of making zeolite with<br>high purity and thereby showed that zeolite is a good adsorbent for wastewater treatment</p><p>&nbsp;</p> <br><p></p>