New physicochemical interpretations for Adsorption of Trichloroethylene on Activated Carbon: Steric and Energetic Interpretation using Statistical Physics Approach

Experimental adsorption isotherms of trichloroethylene (TCE) on activated carbon at four temperatures were analyzed theoretically by a double layer with one energy established through statistical physics approach. This model contains three parameters affecting the adsorption process i.e. the number of molecules per site n, the monolayer adsorbed quantity Q0 and the concentration at half- saturation c1/2. In this work, we propose a steric and energetic interpretation for the different adsorption isotherms of TCE on activated carbon. We calculate also the thermodynamic functions to characterize the adsorption process such as, entropy, free energy, and internal energy as function concentration. The different parameters and the thermodynamic functions were discussed with temperature

Homogenous UV/Periodate Process for the Treatment of Acid Orange 10 Polluted Water

The photoactivated periodate (UV/IO4−) process is used to investigate the degradation of acid orange 10 (AO10) dye. The photodecomposition of periodate ions produces highly reactive radicals (i.e., •OH, IO3•, and IO4•) that accelerate dye degradation. Increasing the initial concentration of periodate to 3 mM enhances the dye removal rate, but over 3 mM periodate, the degradation rate slows down. On the contrary, increasing initial dye concentrations reduces the degradation performance. pH is the most critical factor in AO10 breakdown. Salts slow down the degradation of the dye. However, UV/IO4− is more efficient in distilled water than natural water. Even at low concentrations, surfactants may affect the dye’s decomposition rate. The addition of sucrose reduced the breakdown of AO10. Although tertbutanol is a very effective •OH radical scavenger, it does not affect the dye breakdown even at the highest concentrations. Accordingly, the AO10 degradation is a non-•OH pathway route. According to retrieved data, the photoactivated periodate method eliminated 56.5 and 60.5% of the initial COD after 60 and 120 min of treatment time; therefore, it can be concluded that the UV/IO4− system may treat effluents, especially those containing textile dyes

An innovative in-situ DRAINage system for advanced groundwater reactive TREATment (in-DRAIN-TREAT)

The removal of groundwater contamination is a complex process due to the hydro-geochemical characteristics of the specific site, related maintenance and the possible presence of several types of pollutants, both organic and inorganic. In recent decades, there has been an increasing drive towards more sustainable treatment for contaminated groundwater as opposed to “intensive” treatments, i.e. with high requirements for onsite infrastructure, energy and resource use. In this study, a new remediation technology is proposed, combining the use of advanced drainage systems with adsorption processes, termed “In-situ reactive DRAINage system for groundwater TREATment” (In-DRAIN-TREAT). By taking advantage of the groundwater natural gradient, In-DRAIN-TREAT collects the contaminated groundwater via a drainage system and treats the polluted water directly into an active cell located downstream, avoiding external energy inputs. Preliminary results indicate the applicability and high efficiency of In-DRAIN-TREAT when compared with a permeable reactive barrier (PRB). In-DRAIN-TREAT is applied to remediate a theoretical aquifer with low permeability, contaminated by a 13 m wide hexavalent chromium (CrVI) plume. This is achieved in less than a year, via a drain DN500, 32 m long, a 30 m3 treatment cell filled with activated carbon and no energy consumption. A comparison with permeable barriers also shows a preliminary 63% volume reduction, with a related 10% decrease of remediation costs

Experimental and simulation study of the restoration of a thallium (I)-contaminated aquifer by Permeable Adsorptive Barriers (PABs)

Permeable Adsorptive Barriers (PABs), filled with a commercial activated carbon, are tested as a technique for the remediation of a thallium (I)-contaminated aquifer located in the south of Italy. Thallium adsorption capacity of the activated carbon is experimentally determined through dedicated laboratory tests, allowing to obtain the main modelling parameters to describe the adsorption phenomena within the barrier. A 2D numerical model, solved by using a finite element approach via COMSOL Multi-physics®, is used to simulate the contaminant transport within the aquifer and for the PAB design. Investigations are carried out on an innovative barrier configuration, called Discontinuous Permeable Adsorptive Barrier (PAB-D). In addition, an optimization procedure is followed to determine the optimum PAB-D parameters, and to evaluate the total costs of the intervention. A PAB-D made by an array of wells having a diameter of 1.5 m and spaced at a distance of 4 m from each other, is shown to be the most cost-effective of those tested, and ensures the aquifer restoration within 80 years. The simulation outcomes demonstrate that the designed PAB-D is an effective tool for the remediation of the aquifer under analysis, since the contaminant concentration downstream of the barrier is below the thallium regulatory limit for groundwater, also accounting for possible desorption phenomena. Finally, the best PAB-D configuration is compared with a continuous barrier (PAB-C), resulting in a 32% saving of adsorbing material volume, and 36% of the overall costs for the PAB-D

Statistical model 'Life Cycle Cost-Reliability' for a new mass transit vehicle

Computational Mechanics Inc. US

A modelling analysis of PCE/TCE mixture adsorption based on Ideal Adsorbed Solution Theory

For a proper design of multicomponent adsorption systems, the availability of reliable adsorption models is paramount. In this work, an experimental and modelling analysis of PCE/TCE adsorption, aimed at investigating adsorption capacities in a binary system, is carried out. All the experimental tests are conducted at constant pH and temperature. The analyte concentration is varied over a wide range in order to cover as much as possible real cases that could lead to different adsorption behaviours and, consequently, to different modelling results. Experimental data show that the PCE adsorption capacity does not depend on TCE presence, and the equilibrium final conditions are not related to different analyte adsorption rates. The equilibrium adsorption data are analyzed by using different adsorption models, namely Langmuir multicomponent, Ideal Adsorbed Solution Theory (IAST) and Predictive Real Adsorbed Solution Theory (PRAST) models. The Langmuir model provides the worst data prediction since its basic hypotheses do not reflect the physical behaviour of the system. The IAST model does not provide a satisfactory prediction of binary data except for low liquid concentration levels, as it underestimates the PCE adsorption capacity and overestimates TCE. It follows that when the solid coverage increases, the PCE-TCE mixture behaviour is not ideal. Finally, the PRAST model, here developed for liquid systems for the first time, is considered in order to take into account a non-ideal system by including activity coefficients. The PRAST model provides a very good prediction of PCE adsorption experimental data but it is not useful to predict TCE adsorption data, its performance being even worse than IAST. The inability of the model to correctly predict both isotherms simultaneously lies in the particular type of non-ideality of the system itself, as shown by experimental data

Chemical demulsification of model water-in-oil emulsions with low water content by means of ionic liquids

The demulsification of model water-in-oil (w/o) emulsions containing 1% wt. water by [Omim][PF6] and Aliquat® 336 ionic liquids (IL) as demulsifiers was investigated in batch mode at different temperatures (30, 45 and 60 °C) and demulsifier concentrations (2.5×10‒3, 1.2×10‒2 and 2.9×10‒2 mol L‒1). The model oil is a mixture n-heptane/toluene (70/30% wt.) with 1% wt. of Span® 83 as a surfactant. Experimental results showed that the main differences in demulsification dynamics between systems containing IL and blank (i.e., in the absence of demulsifier) are detected at 30 °C and for short demulsification times (t≤4 h). In particular, the demulsification efficiency is 8, 21 and 74% for the blank sample, [Omim][PF6] and Aliquat® 336 tested under the more concentrated IL condition, respectively. The superior demulsification performances of Aliquat® 336 with respect to [Omim][PF6] were related to the greater molecular weight and more hydrophobic character of its cation, likely able to induce a faster desorption of the surfactant at the w/o interface and consequently promoting water droplet coalescence. Moreover, the kinetic demulsification data were successfully interpreted by an empirical pseudo-first order model. In general, the obtained outcomes encourage future research efforts in the use of ionic liquids for the removal of low water fractions from w/o emulsions