1,721,116 research outputs found
Electrokinetic mobilization of inorganic contaminants from dredged sediment
No full textThe management of dredged sediment is commonly recognized as a complex procedure in industrialized countries, where sediments are often contaminated by metals and organic contaminants due to the presence of a number of point and diffuse contamination sources (i.e., river and coastal discharges, shipping, yacht maintenance). Due to the huge amounts to be dredged every year due to harbor maintenance or environmental dredging activities, the identification of management options different from landfilling is claimed. The valorization of dredged sediments in application typical of the civil and environmental sector (i.e., road construction, embankments, structural materials formulation) usually needs a pretreatment stage aimed at improving the physical (water content, grain size distribution) and chemical properties (pollutants content, salt concentration) of the sediments.
Among the available treatment options, Electrokinetic Remediation (EKR) seems to be particularly suitable due to a number of potential advantages, like the capability of treating fine graded and low-permeability matrices such as sediments, and the ability to remove organic and inorganic contaminants.
EKR is based on the application of an electric field, originated from electrodes immersed in aqueous solutions (anodic and cathodic solutions), to a portion of the contaminated sediment so as to promote the mobilization of the contaminants. The application of EK to contaminated porous media induces the mobilization of ions towards the electrodes due to electromigration. electroosmosis, and electrophoresis. In order to improve the remediation process is possible to use enhancement agents like acids, chelating agents, surfactants added in electrode compartments. In particular, for the metals removal the use of the acids seems to be a promising strategy. However, due to the complexity of both the sediment matrix and the contaminants nature, despite the interest demonstrated by the scientific sector in EK, the uncertainties in process yields and control still hinder the full-scale application.
The aim of this work consists in the study of lab-scale experiments of EKR carried out on metal contaminated sediment samples, collected in three Italian harbors. The EKR tests were performed using different types of agents, namely acetic, nitric and hydrochloric acid, EDTA and ascorbic acid. Each sample was characterized before the EKR test so as to determine: water content, grain size distribution, pH, Acid Neutralization Capacity (ANC), metal content, metal speciation and electrical resistivity. The results showed that the most critical elements were Cu, Cr, Ni, Cd, Pb and Zn, as they were present at concentrations above the limits defined by the Italian Ministry for the Environment.
The EKR tests, performed in plexiglass cells, were conducted using the same conditions in terms of current density, while the duration of the tests and the dosages of the extracting agents were varied, in order to understand the best enhancement conditions on the basis of metals removal and metals mobilization results and to identify the parameters that can hinder the treatment. Furthermore during the treatment the electrical resistivity was monitored in order observe whether this physical parameter could provide information on the progress of decontamination.
Main conclusions:
The use of acids in order to neutralize the basic front produced at the cathode was found to be the best strategy in enhanced electrokinetics tests on dredging sediments. The tests also evidenced that the process was influenced by several factors: treatment time, properties of the matrix (buffering capacity) and of metals (metal fractionation).
It was also observed the nonexistence of a condition of equilibrium between the process fluids and the matrix treated, hence it was not possible apply the prediction models generally used for the description of the chemical reactions.
The monitoring of the electrical resistivity shown that through this parameter is not possible evaluate the migration of the metals during the treatment, likely due to the increase of the ionic content in the system caused by the addiction of the extracting agents. If this hypothesis is confirmed, the monitoring of the electrical resistivity could be used to evaluate the migration of the enhancing agents through the specimen and at this regard, further investigations are in progress
May Pouch Volume and Shape Influence GERD Symptoms Resolution After Conversional Roux-en-Y Gastric Bypass for Sleeve Gastrectomy Related Erosive Esophagitis?
No full textA useful manoeuvre to semplify sellar floor repair following endoscopic transnasal pituitary surgery
No full textReply to letter to the editor: Misleading conclusions on the effects of sleeve gastrectomy on body composition due to statistical errors
No full textBariatric surgery in the setting of liver cirrhosis with portal hypertension: the confection and particularities of Roux-en-Y gastric bypass in a high-risk patient
No full textIntroduction: Morbid obesity is associated with the occurrence of non-alcoholic fatty liver disease, which may progress to cirrhosis. Although weight loss is the treatment of choice, surgical management can be challenging at the stage of cirrhosis. The aim of this video report is to present the confection and the features of a Roux-en-Y gastric bypass (RYGB) in the setting of liver cirrhosis. Methods: We present the case of a 60-year-old man with a weight of 115 kg and a corresponding BMI of 38.9 kg/m2, with non-alcoholic steatohepatitis (NASH)-related liver cirrhosis. The latter was compensated (Child–Turcott–Pugh score at A6) but the patient had already undergone three esophageal variceal ligations. Portal hypertension with splenomegaly was clearly visible on preoperative workup. Results: In this video, we show how to perform RYGB in a case of liver cirrhosis, with a focus on common pitfalls. The main risks remain perioperative bleeding due to portal hypertension and impaired coagulation, as well as the decompensation of the cirrhosis. A careful preoperative nutritional and hepatological evaluation is mandatory since the perioperative risk of morbidities is higher. Conclusion: RYGB is a feasible option in selected patients with morbid obesity and cirrhosis. These patients ideally should be managed in centers having experience in bariatric surgery and hepatology
Attualità in tema di valvola peritoneo-giugulare di Le Veen in pazienti epatopatici in regime di day hospital
No full textImpianto di valvola peritoneo-giugulare di Le Veen in pazienti Epatopatici in day-hospital.
No full textVery low-calorie diet, the morbidly obese with liver cirrhosis and bariatric surgery
No full textNo Abstract availabl
Low Molecular Weight Heparin in Liver Transplant Recipients After Sleeve Gastrectomy
No full textNo abstract availabl
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