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Chromium is one of the most widely used heavy metals in industry as it has enough advantages for tanneries, textiles, wood processing and agro-food industries. Chromium VI is highly toxic and highly soluble in water, which is the origin of its great mobility in the ecosystems. In this study, the forward osmosis (FO) process was investigated to remove chromium from aqueous solution using cellulose triacetate membrane and ammonium bicarbonate (NH4 HCO3 ) as draw solution. The effect of various operating parameters such as feed temperature, feed concentration, draw temperature and draw concentration on FO performance was evaluated. The experimental runs showed that the permeate flux was enhanced with draw temperature, and maximum permeate flux of 2.38 × 10–6 m s–1 was obtained at 55°C. The permeate flux was found to decrease with feed concentration. Moreover, the flux reached 2.9 × 10–6 m s–1 at maximum draw concentration of 3 mol L–1. These operating parameters had insignificant effect on chromium rejection and reached, in all cases, more than 99%. The validation of the model, using McCutcheon and Elimelech model, shows a good agreement with the determined experiment alones. [ABSTRACT FROM AUTHOR]

In the present work, the removal of nitrate from aqueous solution by direct contact membrane distillation (DCMD) using flat sheets polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes was studied. Effect of operating parameters, such as feed temperature, feed flow rate, initial nitrate concentration, feed ionic strength, and competing co-existing anions on permeate flux and nitrate rejection, was investigated. In all DCMD experimental runs, an almost complete nitrate rejection was achieved (higher than 99.90%) and the permeate nitrate concentration was largely below the maximum permissible level in potable water. Under the same operating conditions, PVDF hydrophobic membrane showed a higher permeate flux of 37.21 L/m2h than PP membrane with a permeate flux of 4.12 L/m2h. For both the membranes, feed temperature is the important operating parameter which enhanced exponentially the permeate flux. Likewise, a positive effect on permeate flux was found when feed flow rate was increased. However, no significant effect was found by varying initial nitrate concentration, feed ionic strength, and the presence of co-existing anions on DCMD permeate flux or nitrate rejection efficiency. [ABSTRACT FROM AUTHOR]