Membrane Performance Evaluation for Desalination

Performance evaluation of surface-modified membranes was investigated. The permeation tests were carried out in a crossflow, flat-sheet testing cell for brackish water desalination unit at ambient temperature and under operating pressure up to 25 bar; the feed solution tank had capacity of 20 L. The effective surface membrane area was (54 cm²). Synthetic feed solution was prepared using sodium chloride (1 g/L) and calcium chloride (0.2 g/L) with total salinity of 1000–1050 ppm. Experiments were operated at constant pressure of 20 bar. Membrane samples underwent permeation test for 4 h using distilled water before testing.
The total permeate flux (J) of the tested solution was determined from Equation (1):
where Q is the permeate mass in kg; A is membrane active area in m²; and t is time in hour
The rejection (R) was calculated as Equation (2): $$\mathrm{R}\%=\frac{({\mathrm{C}}_{\mathrm{f}}-{\mathrm{C}}_{\mathrm{P}})\times 100}{{\mathrm{C}}_{\mathrm{f}}}$$
where C_f is the concentration of the salt-feed solution, and C_p is the concentration of salt in permeate.