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This work addresses the selective recovery of platinum group metals (PGMs) from aqueous streams, a critical issue within the recycling and metal refining industries aiming to lose zero of the value contained. Herein, selective PGM capture was investigated using three metal-capturing polymeric resins from different manufacturers: a special anion exchanger (Dow), an S-containing chelating resin (Lanxess), and a phosphine oxide containing coordinating resin (Magpie Polymers). The relative affinity of these different materials for the PGMs, as well as copper, was compared under various conditions. It was found that the phosphine oxide based material was the most suitable for the selective capture of PGMs from an oxidizing solution containing high concentrations of copper and counterions. Theoretical calculations using density functional theory (DFT) have shown that the most likely binding of PGMs to this material is a bidentate coordination via the phosphine oxide groups. more...

Pareto optimization approach was used in searching for the particular successions of topologies and operating conditions for a semicontinuous water network (batch with respect to the raw materials) that minimize both the freshwater consumption and the investment and operating costs. The semicontinuous wastewater network (SWN) formed of N water-using units (WUs), each handling at most K contaminants, and one storage tank (ST) is optimized on time intervals by increasing the wastewater reuse opportunities. A single freshwater source is available and later a regeneration unit (RU) is added to the network as a fine-tuning tool in the Pareto optimization, and further its influence is discussed. The WUs are ordered simultaneously by schedule and by maximum allowable outlet concentrations of contaminants. Thus, the rules concerning the internal reuse between the overlapping WUs correspond to an oriented graph: no recycle is allowed against the ordered sequence. The differential-algebraic equations model consisting in a set of differential equations for the ST and a nonlinear system mass balance equations with restrictions for the overlapping WUs is optimized using the Matlab built in functions for both the genetic algorithms (GA) and the RK-type integrator. The topology of the SWN changes for each time interval, its optimal structure depending upon the minimum freshwater consumption and the costs. A complex synthetic case study was subjected to optimization, and several scenarios are analyzed. more...

The residence time distribution (RTD) approach was used to characterize the flow and mixing behavior of burners. This analysis consists of injecting an inert gaseous tracer into the feed and measuring its change in concentration at various detection points. The responses are then used to characterize the flow behavior and, thus, the local mixing in the space delimited by the injection and probe points. The outcome of this RTD analysis is a flow model that, combined with an appropriate kinetics, constitutes an efficient tool in examining the ways to reduce NOx emissions in existing installations. A replica made in plastic at a 1:1 scale of an industrial gas burner was used for cold experiments. As preliminary information, a chart of local mixing in the axial section of the burner chamber was obtained. Even though far from working conditions, cold experiments are beneficial because they reveal the existence of possible major flow disturbances, leading to imperfect or incomplete combustion, a source of NOx. more...

A water network (WN) for a batch process could be seen as a dynamic structure which changes its topology at fixed time intervals delimited by events. During each time interval, the WN could be abst... more...

The optimization of an integrated network of water-using (WU) and treatment (TU) units is addressed in this paper, by targeting for maximum treated water reuse as a considerably better alternative to fresh water consumption. An optimal integrated water network (WN) is an oriented graph, starting with inlet contaminant free WUs and then the other WUs ranked by a certain criteria. The outlet wastewater streams are either split to be reused by the next WUs in sequence or sent to treatment. The mathematical model of the integrated WN is based upon total and contaminant species mass balances for each and every WU/TU which is restricted with respect to the inlet and outlet contaminant concentrations. The performance of the approach is tested on a synthetic example. Several scenarios were used, the results being analyzed in connection with the reduction of fresh water consumption and the increase of internal and treated water reuse. more...