Feasibility of Forward Osmosis to Recover Textile Dyes Using Single Salts and Multicomponent Draw Solutions.

The textile industry generates large volumes of water characterized mainly by an intense color coming from dyes that are difficult to process due to their synthetic base and the presence of aromatic components. Due to the stricter regulation on the discharge of these effluents, in order to reduce dye waste before discharge into natural channels, alternatives are being sought to manage this wastewater. In this work, the concentration of dyes in simulated wastewater from the textile industry was studied by forward osmosis (with a cellulose triacetate CTA membrane), with the aim of concentrating the dye for its future recovery and reincorporation into the production process. Two dyes of different nature were evaluated to study the efficiency of the proposed process, using NaCl and reverse osmosis brine from a model seawater desalination solution as extraction solutions. It was observed that dye type (reactive or direct) and their charge influence the color rejection with the forward osmosis membrane used. It was able to concentrate the dyes in the feed solution up to approximately 55% with the reverse osmosis brine from the model seawater desalination solution. Finally, the results demonstrate that the FO process is a promising option for concentrating dyes present in wastewater from the textile industry in order to reuse them in the dyeing process.

Theoretical Model for the Prediction of Water Flux during the Concentration of an Olive Mill Wastewater Model Solution by Means of Forward Osmosis.

Currently, understanding the dynamics of the interaction between the agents in a process is one of the most important factors regarding its operation and design. Membrane processes for industrial wastewater management are not strangers to this topic. One such example is the concentration of compounds with high added value, such as the phenolic compounds present in olive mill wastewater (OMW). This process is a viable option, thanks to the forward osmosis (FO) process, osmotically driven by a saline stream. In this context, the transport of the solute and the solvent through the FO membranes, although essential to the process, remains problematic. This paper presents a study to predict, by means of a theoretical model, the water flux for two membranes (a cellulose triacetate flat sheet and a polyamide hollow fiber with integrated aquaporin proteins) with different characteristics using a sodium chloride solution as the draw solution (DS). The novelty of this model is the consideration of the contribution of organic compounds (in addition to the inorganic salts) to the osmotic pressure in the feed side. Moreover, the geometry of the modules and the characteristics of the membranes were also considered. The model was developed with the ability to run under different conditions, with or without tyrosol (the compound chosen as representative of OMW phenolic compounds) in the feed solution (FS), and was fitted and evaluated using experimental data. The results presented a variability in the model prediction, which was a function of both the membrane used and the FS and DS, with a greater influence of tyrosol observed on the permeate flux in the flat cellulose triacetate membrane.

Nitrogen recovery from sludge centrate by membrane contactor: Influence of operating parameters and cleaning conditions.

In urban wastewater treatment, the sludge generated is treated by anaerobic digestion, to be subsequently dehydrated by centrifuges. Currently, the liquid fraction obtained in this dehydration process is recirculated at the head of the treatment plant. However, its high nitrogen and phosphorus content makes it an effluent with high added value. The recovery of these nutrients could be an excellent alternative for the production of fertilizers or other industrial applications. In this study, the use of a liquid-liquid phase membrane contactor is presented as a favorable solution for the recovery of ammoniacal nitrogen from sludge centrated. The polypropylene hollow fiber membrane was evaluated considering its ammonia removal and recovery capacity. For this, different parameters were evaluated: the influence of the type and concentration of the acid solution, the wastewater pH, the flow rates of feeding and the acid stripping solution, and the contact time. Results showed that with a contact time of 65 min, ammonia removal and recovery percentages of the order of 90% were achieved. The flow rates of the stripping and feed solutions together with the acid concentration did not have a significant influence on the removal but on the recovery. Concerning used acid, sulphuric and phosphoric acid solutions achieved better results than nitric acid solution. The most critical parameter was the pH, obtaining the highest removal and recovery of ammonium at the highest pH. Finally, a stable cleaning protocol was obtained, between preventive and moderate cleanings to avoid severe cleanings, keeping the membrane at its maximum capacity.

Copper Recovery From Ammonia Solutions Through Electro-Electrodialysis (EED).

Alkaline leaching with highly selective ammoniacal complexing agents is an interesting alternative for the treatment of copper concentrates. This treatment is beneficial for copper recovery because it allows the formation of soluble amines complexes, with cupric tetramine (  Cu ( NH 3 ) 4 2 + ) being the most stable. In order to suppress the unit operation of solvent extraction (SX) and move directly to the electrochemical process, an electro-electrodialysis (EED) process using ion exchange membranes to obtain copper is proposed. The study contemplates the operation with synthetic ammonia solutions containing copper at different concentrations and current density under standard conditions of pressure and temperature. The presented data demonstrate that the concentration of copper in the solution and the excess of ammonia are inversely related to the efficiency of the current and the voltage of the cell, whereas an increase in current density causes an increase in current efficiency, contrary to what happens in sulfuric systems.