Nanofiltration operating results

The rejection against As(V) versus the operation pressure of the above composite NF membrane is shown in Figure 11.6. The rejection for the As(V) was about 97% at a transmembrane pressure of 0.3 MPa and a water flux around 32 L m" h At a feed As(V) concentration of 360 xg, one throughout using the nanofiltration membrane results in a permeate water quality slightly higher than the WHO MCE limit of 10 xg level. At elevated operation transmembrane pressure, the rejection increases, leading to a lower permeate arsenic concentration. At 0.4 MPa, the permeate As(V) concentration is lower than 10 xg and the water flux reaches about 43 L m h . These... 

Mehiguene, K., Garba, Y, Taha, S., Gondrexon, N. Dorange, G. (1999) Influence of operating conditions on the retention of copper and cadmium in aqueous solutions by nanofiltration experimental results and modelling. Separation and Purification Technology, 15 (2), 181-187. 

While a number of dendritic catalysts have been described, catalyst recyclization in most cases is an unsolved problem. Diaminopropyl-type dendrimers bearing Pd-phosphine complexes have been retained by ultra- or nanofiltration membranes, and the constructs have been used as catalysts for allylic substitution in a continuously operating chemzyme membrane reactor (CMR) (Brinkmann, 1999). Retention rates were found to be higher than 99.9%, resulting in a sixfold increase in the total turnover number (TTN) for the Pd catalyst. 

A complete process scheme for regeneration and reuse of spent final rinse water from an electroless plating operation has been developed by Wong et al. [105]. It includes (i) pre-treatment by microfiltration, UV irradiation, carbon adsorption (ii) heavy metal removal by nanofiltration and (iii) polishing using an ion exchange mixed bed. The results of a pilot study showed that high quality product water with an overall water recovery of 90% could be produced with an estimated payback period of less than 18 months. 

Kragl et al.100 described the retention of diaminopropyl-type metallodendrimers bearing palladium phosphine complexes on ultra- or nanofiltration membranes and their use as catalysts for allylic substitution in a continuously operating chemical membrane reactor. Their results demonstrated a viable procedure for catalyst recovery, because these metallodendrimers acting as catalyst supports offered an advantage in that the intrinsic viscosity of the solution is smaller, facilitating filtration. 

The removal of MTBE by membrane micro- or ultrafiltration is highly ineffective due to the molecule s small size. Only nanofiltration showed removal potential. However, the process is very elaborate and expensive in terms of equipment and operating conditions (low transmembrane flux, high membrane area). Moreover, the resulting water needs further treatment in order to comply with drinking water standards, and the concentrate has to be treated before discharged. 

Effects of operating pressure on permeate flux value and rejection value during the total circulation experiments are shown in Figure 22.6. Operating pressure had little effect on the rejection value. Permeate flux value increased linearly with operating pressure up to 4 MPa. Once the operating pressure exceeded 4 MPa, permeate flux did not increase linearly. Therefore, suitable operating pressure for separation of anserine and carnosine with the nanofiltration membranes was determined to be 4 MPa. Similar results were obtained with other membranes. 

Type 1 or type 3 can describe results from CRECEP, TZW nanofiltration filtrate, WRC, Kiwa and LHRSP. Peak contamination (type 3) appeared in the first weeks in 30-minute stagnation samples (no data exist for longer stagnation times during the first month). After about 2 months operation, copper concentrations decreased to a minimum with some variation which could be explained (probably) 1 changes in water quality (pH, temperature, oxygen, etc.). 

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