A Brief Comparative Study on Removal of Toxic Dyes by Different Types of Clay

Increasing amount of organic dyes in the ecosystem particularly in wastewater has propelled the search for more efficient low-cost bio adsorbents. Different techniques have been used for the treatment of wastewater containing toxic dyes such as: biological degradation, oxidation, adsorption, reverse osmosis, and membrane filtration. Among all these processes mentioned, adsorption with low cost adsorbents has been recognized as one of the cost effective and efficient techniques for treatment of industrial wastewater from organic and inorganic pollutants. Clays as material adsorbents for the removal of various toxic dyes from aqueous solutions as potential alternatives to activated carbons has recently received widespread attention because of the environmental-friendly nature of clay materials. This chapter presents a comprehensive account of the techniques used for the removal of industrial cationic and anionic dyes from water during the last 10 years with special reference to the adsorption by using low cost materials in decontamination processes. Effects of different adsorption parameters on the performance of clays as adsorbents have been also discussed. Various challenges encountered in using clay materials are highlighted and a number of future prospects for the adsorbents are proposed

Contribution a l'etude electrochimique des interfaces : interactions matiere organique adsorbee-anions lourds en liaison avec les enrichissements en selenium des particules marines

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

EVALUATION OF CONSTRUCTION MANAGEMENT CONTRACTS IN DEVELOPING COUNTRIES

Developing countries face many formidable obstacles in their development process. Local inflation, material scarcity, slowly developing native technical and managerial talents, heavy international debts, and world wide inflation are dramatically affecting the development programs of developing countries. These problems demand the utilization of the most effective management and technical methods at their disposal in order to achieve their development goal. There are three main project delivery systems that owners from developing countries can use in executing their construction programs. The traditional Engineer, Procure and Construct system (EPC); the Design-build (Turnkey) system, and the Construction Management (CM) system are the main three project delivery systems discussed in this research. The thesis concentrates on analyzing the construction management system, since the traditional and the Turnkey systems are very well known and have been extensively used in developing countries. The process of selecting the appropriate project delivery system that responds to the project\u27s nature and the owner\u27s requirements is a very important step that may significantly affect the success or failure of the project. A Project Delivery Selection Model (PDSM), and a Project Delivery Decision Model (PDDM) were developed to evaluate the owner\u27s requirements, the developing country\u27s characteristics, and the project\u27s nature. These models are very easy to use, a requirement for owner\u27s from developing countries, yet they provide meaningful results that the owner can use in making his selection of the most suitable project delivery system. A survey questionnaire mailed to companies that provide construction management services in developing countries was utilized in identifying the parameters and attributes of construction management and developing countries used in the two models. The construction management system has had mixed results in the United States, but both its opponents and proponents agree that the system has a lot to offer once it is used on the appropriate project and in the right circumstances. These appropriate projects and circumstances are even more important for developing countries, where additional problems may also be present. These problems may be caused by the nature of the construction management system, or by the technical and managerial deficiencies of developing countries. The author examined these problems and recommended the appropriate modifications

Equilibrium and thermodynamic studies for the removal of As(V) ions from aqueous solution using dried plants as adsorbents

This paper reports the feasibility of using dried plants to remove As(V) from aqueous solution under different experimental conditions. For this purpose, micro-particles of both Calami rhizoma and Withania frutescens plants, have been separately used without pre-treatment as natural adsorbents. Effect of various process parameters, namely adsorbent dose, contact time, initial As(V) concentration, temperature, and pH has been studied. The experimental data were analyzed using Freundlich, Langmuir, and Temkin isotherm models to determine the mechanistic parameters related to the adsorption process. It was found that the Langmuir and Freundlich models fitted well. Thermodynamic parameters, viz, free energy change (ΔG0), enthalpy change (ΔH0), and entropy change (ΔS0), were also determined. The negative values of free energy change indicated the spontaneous nature of the adsorption and the positive values of enthalpy change suggested the endothermic nature of the adsorption process. The presence of some competing ions like Cl−, NO3-, Mg2+, Cd2+, Cu2+, and Zn2+ did not affect the arsenate uptake or removal, whereas HPO42- strongly interfered negatively

Orthophosphate ion adsorption onto raw shrimp shells

The aim of this work was to develop new low-cost adsorbents obtained from animal origins, available in large quantities and environmentally friendly. Raw shrimp shell (RSS), a biomaterial of animal origin, is abundant, available, renewable and non-toxic. It has physicochemical properties that can induce a significant adsorptive activity. In this study, the removal of phosphate anions (H2PO4-, HPO42-) from aqueous solution by adsorption onto raw shrimp shells was studied. The surface micro-morphology of the biomaterial was investigated using scanning electron microscope and qualitative element composition was analyzed using energy dispersive X-ray and infrared spectroscopies. The efficiency of the biomaterial was investigated using a batch adsorption technique under different experiment conditions, achieved by varying parameters such as adsorbent dosage, the contact time, the initial phosphate anion concentrations, the temperature and the initial solution pH. Results show that the kinetics adsorption of phosphate ions by the biomaterial is relatively quick and the biomaterial showed a high adsorption capacity of 0.20 g∙g-1 and 0.4 g∙g-1 for HPO42- and H2PO4-, respectively. The adsorption data were analyzed using the Langmuir, Freundlich and Temkin adsorption isotherms to determine the nature of the adsorption sites. Both Langmuir and Freundlich adsorption models showed good fits to the experimental adsorption data.Cette étude s’inscrit dans le cadre de certains de nos travaux visant la valorisation de matériaux naturels d’origine végétale, animale et minérale pouvant rendre les procédés d’épuration des eaux simples et moins coûteux. Les carapaces de crevettes à l’état brut, biomatériau d’origine animale, entrent dans cette catégorie. Il est abondant, disponible, renouvelable et non toxique, et présente des propriétés physicochimiques qui peuvent induire une activité adsorbante importante. Le biomatériau a été caractérisé par microscopie électronique à balayage, par spectroscopie d’émission X et spectroscopie infrarouge. Une étude complète de l’adsorption des ions phosphates (HPO42- et H2PO4-) sur des carapace de crevettes à l’état brut a été effectuée. L’influence de paramètres physicochimiques tels que la masse d’adsorbant, le temps de contact, le pH, la température et la concentration initiale de phosphate a été étudiée. Les résultats obtenus montrent une cinétique rapide et une grande capacité de ce biomatériau à retenir les ions phosphates pouvant atteindre 0,20 g∙g-1 pour HPO42- et 0,40 g∙g-1 pour H2PO4-. Les isothermes d’adsorption étudiés (Langmuir, Freundlich et Temkin) montrent une bonne corrélation avec les modèles de Langmuir et de Freundlich

Kinetic and equilibrium isotherm studies for the removal of acid blue 113 dye by dried

Water pollution is an alarming problem in developing countries. Dried algae can be considered as potential and suitable bio-sorbents due to their fast and easy growth and high availability. The special surface properties of these algae allow them to adsorb different types of organic and inorganic pollutants from solutions. In this context, the removal of anionic acid blue 113 dye (AB113) from aqueous solutions by dried Corallina officinalis alga as low-cost bio-sorbent was chosen as a case study of a typical remediation process of water contaminants. The effect of various environmental and physicochemical parameters has been studied. The results show that the equilibrium adsorption was established within 120 min. The sorption phenomenon was investigated by determining the process kinetics at different concentrations and the adsorption isotherms at different temperatures. The kinetics results showed that the pseudo second-order kinetics model generates the best agreement with the experimental data. The modeling results showed that linear Langmuir and Freundlich models appear to fit the adsorption data better than Temkin model for the adsorption of AB113 onto dried C. officinalis alga. It can be concluded that C. Officinalis alga can be successfully used as adsorbent