M.T. Montañés

Effect of pH and chloride concentration on the removal of hexavalent chromium in a batch electrocoagulation reactor

In this work, the effect of pH and chloride ions concentration on the removal of Cr(VI) from wastewater by batch electrocoagulation using iron plate electrodes has been investigated. The initial solution pH was adjusted with different concentrations of H(2)SO(4). The presence of chloride ions enhances the anode dissolution due to pitting corrosion. Fe(2+) ions formed during the anode dissolution cause the reduction of Cr(VI) to form Cr(III), which are co-precipitated with Fe(3+) ions at relatively low pH. The reduction degree of Cr(VI) to Cr(III) and the solubility of metal hydroxide species (both chromic and iron hydroxides) depend on pH. At higher concentrations of H(2)SO(4), the reduction of Cr(VI) to Cr(III) by Fe(2+) ions is preferred, but the coagulation of Fe(3+) and Cr(III) is favoured at the lower H(2)SO(4) concentrations.

Evolution with Exposure Time of Copper Corrosion in a Concentrated Lithium Bromide Solution. Characterization of Corrosion Products by Energy-Dispersive X-Ray Analysis and X-Ray Diffraction

Abstract The evolution with the exposure time of copper corrosion in a 400-g/L lithium bromide (LiBr) solution was investigated using electrochemical measurements. The study was carried out under a...

ZnO/ZnS heterostructures for hydrogen production by photoelectrochemical water splitting

This work studies the photoelectrochemical behavior of novel ZnO/ZnS heterostructures obtained by means of anodization in water and glycerol/water/NH4F electrolytes with different Na2S additions under controlled hydrodynamic conditions. For this purpose different techniques such as Field Emission Scanning Electronic Microscopy (FE-SEM) with EDX, Raman spectroscopy and photoelectrochemical water splitting tests under standard AM 1.5 conditions have been carried out. The obtained results showed that the hydrodynamic conditions promoted an ordered nanotubular morphology which facilitates electron–hole separation and consequently, the photoelectrochemical activity for water splitting is enhanced. Additionally, the effect of glycerol in the anodization solutions seems to be beneficial for increasing the dark current photostability.

Effect of Fluid Velocity and Exposure Time on Copper Corrosion in a Concentrated Lithium Bromide Solution

Abstract A study was carried out to investigate the effect of hydrody-namic variables and exposure time on the corrosion of copper in a 4.6-M lithium bromide (LiBr) solution at room temperature usi...

Stabilization/solidification of hot dip galvanizing ash using different binders

This study focuses on solidification of hot dip-galvanizing ash with a high content of zinc and soluble substances. The main purpose of this paper is to immobilize these pollutants into a matrix and allow a safer way for landfill disposal of that waste. Three different binders (Portland cement, fly ash and coal fluidized-bed combustion ash) were used for the waste solidification. Effectiveness of the process was evaluated using leaching test according to EN 12457-4 and by using the variance analysis and the categorical multifactorial test. In the leaching test, four parameters were observed: pH, zinc concentration in leachate, and concentration of chlorides and dissolved substances in leachate. The acquired data was then processed using statistical software to find an optimal solidifying ratio of the addition of binder, water, and waste to the mixture, with the aim to fulfil the requirement for landfill disposal set by the Council Decision 2003/33/EC. The influence on the main observed parameters (relative amount of water and a binder) on the effectiveness of the used method and their influence of measured parameters was also studied.

Influence of Temperature and Reynolds Number on the Galvanic Corrosion of the Copper/AISI 304 Stainless Steel Pair in Lithium Bromide Using a Zero-Resistance Ammeter

The effects of temperature and Reynolds number (Re) on the galvanic corrosion of the copper (UNS C15710)/AISI 304 (UNS S30400) stainless steel pair in a concentrated lithium bromide (LiBr) solution was investigated in a hydraulic circuit using a zero-resistance ammeter. Results show that copper is the anode and that galvanic current density decreases with time because of the formation of a protective film. Initially, galvanic current density increases with Re; however, with time, differences decrease and this tendency is even reversed. As Re increases, greater quantities of corrosion products are initially produced and a thicker film is formed. The galvanic current density increases with temperature, suggesting that the films formed at lower temperatures are less defective and more resistant; however, at the highest flow rate, with time, the galvanic current density is lower at 75°C than at 50°C. This behavior is attributed to the quick and large formation of corrosion products at the highest flow and tem...

Integrating Sustainable Development in Chemical Engineering Education: The Application of an Environmental Management System.

The principles of sustainable development have been integrated in chemical engineering education by means of an environmental management system. These principles have been introduced in the teaching laboratories where students perform their practical classes. In this paper, the implementation of the environmental management system, the problems arisen, the proposed solutions and the obtained results are discussed. The main problems are related to the chronological order of the courses in the chemical engineering degree, the commitment of students and the proper management of wastes. The suggested solutions are a combination of preliminary theoretical explanations, the supply of adequate documents to students and the evaluation of their work from the principles of sustainable development. Results show that after the implementation of the system, it is possible to reduce the consumption of raw materials and resources, and the generation of wastes. Results also suggest an improvement in the skills, attitudes and values of the students according to the sustainable-development principles.

Effect of Temperature and Impurities on the AISI 316L/Microplasma Arc Welded AISI 316L Galvanic Pair in H3PO4 under Flowing Conditions

The authors would like to express their gratitude to the Spanish MAEC (PCI Mediterraneo C/8196/07, C/018046/08, D/023608/09, D/030177/10), to the FPU grant given to Rita Sanchez Tovar and to Dr. Asuncion Jaime for her translation assistance.