Search results for "Dissolution"

Thermogalvanic effects on the corrosion of copper in heavy brine LiBr solutions

2012

Thermogalvanic corrosion of copper in heavy brine LiBr solutions has been investigated using a zero-resistance ammeter (ZRA). The temperature gradients between copper electrodes immersed in the same LiBr solution result in the formation of thermogalvanic cells with hot anodes, leading to high and sustained thermogalvanic currents. Copper loss rates, calculated using Faraday's law, substantially exceed 0.025mmyear -1, a value regarded as the threshold of low corrosion rates. The effects of thermogalvanic coupling on the surface properties of the anode and the cathode have been analysed by means of electrochemical impedance spectroscopy (EIS). The results obtained in this analysis have been r…

Ecotoxicological status of a watercourse recovering from heavy loading by pulp and paper industry

2013

A phenomenological model for the quantitative interpretation of partial suspension conditions in stirred vessels

2000

Publisher Summary Many important chemical engineering operations involve the suspension of solid particles in a liquid phase inside stirred tanks. Relevant examples include adsorption, crystallization, dissolution, leaching, precipitation, ion exchange and catalytic multiphase processes. This chapter describes a phenomenological model for the quantitative determination of the suspended solids mass fraction in stirred tanks operated at partial suspension conditions. Experimental data on fractional suspension, obtained by the “Pressure Gauge Technique” in vessels stirred by a downward-pumping pitched-blade-turbine, are presented. Furthermore, model predicted trends are compared with experimen…

Trace element fractionation through halite crystallisation: Geochemical mechanisms and environmental implications

2019

Halite is an important mineral for industry, agriculture and food production. It crystallises after water evaporation, while the progressive growth of dissolved metal ions in brines is occurring. Then, halite exploitation may provide the delivery of metal ions in the environment and the mechanism of this trace element accumulation should be studied. In this work we investigate the distribution of lanthanides and Y (hereafter named Rare Earth Elements, REE), Zr and Hf between crystallising halite and brines in the Dead Sea as geochemical tools for recognising the mechanism of metal ion removal from brines and accumulation in halite. Halite forms cubic crystals where octahedral planes sometim…

Colloidal stability of nanoparticles derived from simulated cloud-processed mineral dusts

2013

AbstractLaboratory simulation of cloud processing of three model dust types with distinct Fe-content (Moroccan dust, Libyan dust and Etna ash) and reference goethite and ferrihydrite were conducted in order to gain a better understanding of natural nanomaterial inputs and their environmental fate and bioavailability. The resulting nanoparticles (NPs) were characterised for Fe dissolution kinetics, aggregation/size distribution, micromorphology and colloidal stability of particle suspensions using a multi-method approach. We demonstrated that the: (i) acid-leachable Fe concentration was highest in volcanic ash (1mMg−1 dust) and was followed by Libyan and Moroccan dust with an order of magnit…

The closure of water circuits by internal thermophilic (55 and 70�C) anaerobic treatment in the thermomechanical pulping process

1997

The suitability of an internal thermophilic anaerobic treatment system for closing the water circuits in thermomechanical pulp (TMP) production was studied. The dissolution of wood organics in the water circuit was simulated by hot disintegration of TMP pulp, while the water system closure was simulated by repeated hot disintegration of TMP pulp with recirculated water. The upflow anaerobic sludge blanket (UASB) reactors were started at 55 and 70°C with mesophilic inoculum, and stable performances were established within 60 days at both temperatures. Closing the water circuits without internal treatment rapidly resulted in increased chemical oxygen demand (COD) in the recirculated water. In…

Influence of three types of superplasticizers on tricalciumaluminate hydration in presence of gypsum.

2006

International audience; Different types of superplasticizers have been widely used over the past few decades in order to produce a more fluid or very high strength and durable concrete. These chemical admixtures interfere with the various physico-chemical processes occurring in early cement paste. In this paper we present results from a study on the influence of superplasticizers on pure tricalciumaluminate hydration in presence of gypsum. The suspensions hydration has been investigated by conductimetry, isothermal calorimetry and total organic carbon analysis of the liquid phase. The time taken for ettringite formation has been determined without superplasticizer and in presence of three d…

Optimization of the coagulation–flocculation treatment: influence of rapid mix parameters

1999

[EN] Turbid waters, containing suspended and colloidal particles, are normally treated by coagulation–flocculation followed by clarification; the process usually consists of the rapid dispersal of a coagulant into the raw water followed by an intense agitation commonly defined as rapid mixing. Rapid mixing is influenced by chemical and physical parameters and the final result of the whole treatment depends on this step. The study focused on the most important parameters of rapid mix design: velocity gradient and rapid mix time. Wastewaters from a tannery processing stored ovine hides were treated with aluminium(III) or iron(III) salts. Experimental results indicate that rapid mix time has a…

Rapid on-line sample dissolution assisted by focused microwave radiation for silicate analysis employing flame atomic absorption spectrometry: iron d…

2004

An on-line automated flow injection system with microwave-assisted sample digestion was used to perform silicate rock dissolution in acid medium for iron determination. For this purpose, a continuous flow system was built up by using an automatic flow injection analysis (FIA) system coupled to a flame atomic absorption spectrometer (FAAS), including a focused microwave oven unit. Inside the microwave cavity was inserted a polytetrafluoroethylene (PTFE) reactor coil (300cm length and 0.8mm i.d.) where the dissolution takes place. Chemical and flow variables as well as iron determination parameters were studied. In the flow system, a slurry of the rock sample (50mg in 200ml of acid mixture HF…

FTIR approaches for diuron determination in commercial pesticide formulations.

2005

Two strategies have been developed for Diuron determination by FTIR spectrometry, an off-line extraction and stopped-flow determination and a fully mechanized procedure, based on the on-line extraction of Diuron and FIA-FTIR measurement of the extracts. The aforementioned procedures have been compared with a reference chromatographic method. The off-line FTIR spectra were obtained at a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) by accumulating 25 scans. Diuron was determined using peak height measurements at 1582 cm(-1) corrected using a baseline defined between 1562 and 1614 cm(-1). The waste generation of the off-line procedure was 3.4 mL chloroform for each sample, and the me…