الفهرس 
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Abstract
Enviromental contamination of air, water and soil has become a threat to the continued existence of human, animals and plants. The industrial processes are one of the main sources of enviromental contamination. In recent decades, a class of anionic clays known as layered double hydroxides (LDHs) or hydrotalcite-like compounds (HTlc) has attracted substantial attention from both industry and academia. Although LDHs exist as naturally occurring minerals, they are also relatively simple and economical to synthesize. The structure of LDHs is based on positively charged brucite-like sheets and the positive charges are balanced by intercalation of anions in the hydrated interlayer regions. LDHs have relatively weak interlayer bonding and, as a consequence, exhibit excellent ability to capture organic and inorganic anions. The most interesting properties of LDHs include large surface area, high anion exchange capacity, that is comparable to those of anion exchange resins, reconstruction of calcined LDH by the memory effect and good thermal stability.
LDHs have been studied for their potential use in a wide range of important areas, i.e. catalysis, photochemistry, electrochemistry, polymerization, magnetization, biomedical science, and environmental application. There has also been considerable interest in using LDHs to remove environmental contaminants since environmental pollution has emerged as an important issue in the recent decades.
Indeed, increasing interest has recently been diverted to evaluating the ability of LDHs to remove inorganic and organic contaminants such as oxyanions and dyes from aqueous solutions by the process of adsorption and ion exchange.
In this concern, the present work is directed to study the preparation of different LDHs and evaluation of the products’ ability to sorb some anionic contaminants, namely; chromium (VI) as an oxyanion and congo red as a dye.
The main plan of this work includes:
1- Synthesis of different layered double hydroxides (LDHs).
2- Characterization of the synthesized LDHs with different analytical techniques.
3- Evaluation for the synthesized LDHs ability to sorb some anionic contaminants from aqueous medium.
4- Studying the factors effecting on the sorption of anionic contaminants by LDHs.
5- Studing the sorption isotherms and kinetics to investigate the mechanism and the type of the sorption process and determination of the thermodynamic parameters.
6- Investigation the recyclability of the prepared LDHs.