부산대학교 도서관

[Display omitted] • MDC was applied for the first time to obtain calcium nitrate crystals. • Hydrophobic PVDF/Span 85 membranes were prepared and used in the MD step. • Remarkably higher water contact angle was achieved by adding Span 85 to PVDF. • The permeate flux of the MD process was increased by adding Span 85 to PVDF. • The highest amount of crystals was obtained by adding 4 wt% Span 85 to PVDF. As an alternative to the energy-intensive evaporation-crystallization method, membrane distillation crystallization (MDC) was applied for the first time to obtain calcium nitrate crystals from its aqueous solution. Calcium nitrate solution was obtained through the reaction between calcium carbonate and nitric acid, and then it was concentrated in the membrane distillation (MD) process and further crystallized. The MD step was conducted using hydrophobic polyvinylidene fluoride (PVDF)/sorbitan trioleate (Span 85) membranes. Span 85 was incorporated into the membrane structure in various concentrations to improve the hydrophobicity of membranes, and the resultant membranes were characterized via different methods. In addition, the resultant calcium nitrate crystals were characterized by X-ray fluorescence (XRF) spectroscopy. The MDC results showed that the optimum amount of Span 85 in the polymeric solution was 4%, which led to the formation of a membrane with higher porosity (67.2%) and water contact angle (95.7°) compared to the neat PVDF membrane. The mentioned membrane exhibited the highest water flux in the MD process compared to the other membranes, and also it produced the highest amount of crystals due to its remarkably better performance in the MD step in terms of feed concentration. [ABSTRACT FROM AUTHOR]