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This work addresses the treatment by nanofiltration (NF) of solutions containing NaCN and NH(4)Cl at various pH values. The NF experiments are carried out in a Lab-Unit equipped with NF-270 membranes for model solutions that are surrogates of industrial ammoniacal wastewaters generated in the coke-making processes. The applied pressure is 30 bar. The main objective is the separation of the compounds NaCN and NH(4)Cl and the optimization of this separation as a function of the pH. Membrane performance is highly dependent on solution composition and characteristics, namely on the pH. In fact, the rejection coefficients for the binary model solution containing sodium cyanide are always higher than the rejections coefficients for the ammonium chloride model solution. For ternary solutions (cyanide/ammonium/water) it was observed that for pH values lower than 9 the rejection coefficients to ammonium are well above the ones observed for the cyanides, but for pH values higher than 9.5 there is a drastic decrease in the ammonium rejection coefficients with the increase of the pH. These results take into account the changes that occur in solution, namely, the solute species that are predominant, with the increase of the pH. The fluxes of the model solutions decreased with increased pH.

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A B S T R AC TThis work addresses the assessment of nanofi ltration (NF) in terms of membrane characteristics, operating transmembrane pressure and feed composition for the maximal removal of anionic surfactants in wastewater from a detergent industry. Model solutions of linear alkylbenzene sulphonates (LAS) and sodium lauryl ether sulphates (SLES) covering a wide range of SLES/LAS ratios are used as surrogates of the wastewaters with 0.43 g l −1 of methylene blue active substances (MSAS). The NF experiments are carried out in a unit equipped with NF-90, NF-200 and NF-270 membranes (FilmTec Corp., USA). The applied pressure varied from 15 to 25 bar. The rejection coeffi cients to total organic carbon (TOC) are practically independent of pressure and are higher than 95% for all model solutions and higher than 92% for the wastewater. The SLES solutions have the highest permeation fl uxes of 20-33, 121-207 and 242-371 kg h −1 m −2 for NF90, NF200 and NF270 membranes, respectively. The permeation fl uxes for the other model solutions have intermediate values between the ones of the SLES solution and the ones of the wastewater. These present permeations fl uxes as low as 10-11 kg h −1 m −2 for the NF 200 and the NF 270 membranes.

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