Issue 4

The objective of this study is to elucidate the efficiency of electrosorption on desalination of aqueous NaClsolution using nano-structured carbon aerogel electrodes. The experiments were performed in an electrosorption cell consisting of a pair of carbon aerogel sheets separated by a 0.5cm spacer. The electrosorption performance is investigated with different applied voltages and solution concentrations. It increases with increasing applied voltage, higher concentration gradient and less double-layer overlapping effect. Under the experimental conditions at the optimum applied voltage of 1.2 Volt and initial NaCl concentration 100 - 1000 mg l^-1, the electrosorption capacity was found to be 5.20 - 14.22 mg NaCl/g carbon aerogel.Na⁺ and Cl^- ions are electro-absorbed at the electrical double layer without electron transfer redox reactions at anode and cathode. The good electrosorption performance of carbon aerogel electrodes might be attributed to their high specific area, high electrical conductivity, chemical inertness and optimal pore size distribution for the passage and easy movement of ions during electrosorption and electrodesorption. The process is reversible, as the electrode charge/discharge procedure can be repeated innumerable times without any significant loss of salt sorption capacity in all cycles. 

The performed analysis could be used to quantify the impact of climatic change on evaporation, to determine the accuracy of predicted evaporation against that obtained from the meteorological instruments, and to investigate the alternative values of several meteorological variables in the case of limited data sets. 

This study examines the implication of a market-based system to allocate water regionally in one of the most intensively irrigated areas of Greece. The proposed approach combines elements from administrative allocation and tradable water rights in order to assess several water supply scenarios under growing water scarcity conditions. In this framework, irrigation water demand functions were derived by means of an optimization model that maximizes the expected annual net benefits from water use in agriculture. Then, an inter-district water market model is developed to compute the most effective water allocation at the basin-level. An institutional reform is suggested, that is linked with the creation of effective water users’ associations. The aim of this reform is to achieve a functioning and low-cost trading system at the basin level. The results show that significant volumes of water would be traded under various deficit scenarios, mainly due to the spatial heterogeneity in water use and availability.

In the present study, batch adsorption studies were performed for the removal of malachite green and acid blue 161 dyes from aqueous solutions by varying parameters such as contact time, waste marble dust amount, initial dye concentration and temperature. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin adsorption isotherm models. The Langmuir and Freundlich adsorption models agree well with experimental data. The pseudo-second order, intraparticle intraparticle diffusion and Elovich kinetic models were applied to the experimental data in order to describe the removal mechanism of dye ions by waste marble dust. The pseudo-second order kinetic was the best fit kinetic model for the experimental data. Thermodynamics parameters such as ΔG, ΔH and ΔS were also calculated for the adsorption processes. The experimental data were used to construct an artificial neural network (ANN) model to predict removal of malachite green and acid blue 161 dyes by waste marble dust. A three-layer ANN, an input layer with four neurons, a hidden layer with 12 neurons, and an output layer with one neuron is constructed. Different training algorithms were tested on the model to obtain the proper weights and bias values for ANN model. The results show that waste marble dust is an efficient sorbent for malachite green dye and ANN network, which is easy to implement and is able to model the batch experimental system.