Effects of stirring speed on coupled transport of nitrate ions through liquid membranes

Abstract

In this study, the removal of nitrate NO À 3 À Á ions from aqueous streams with liquid membrane technique has been investigated. Among the other parameters (temperature, pH, acceptor phase type and medium concentration), the stirring speed was chosen as process parameter. From the experimental results, it has been determined that the reaction was diffusion controlled. The transport ef®ciency of nitrate ions increased with increasing stirring speed. The membrane entrance and exit rate constants (k 1d , k 2m and k 2a respectively) were linearly dependent on the stirring speed ratios of 100 to 250 rpm.Coupled transport of nitrate ions through a liquid membrane in 85% n-hexane-15% tricloromethane as diluent, containing tetraoctyl ammonium chloride (TOACl) as a carrier was examined at various stirring speeds. Membrane entrance (k 1d ) and exit rates (k 2m and k 2a ) increase with increasing the stirring speeds. The diffusion of the nitrate ion-carrier complex through the narrow stagnant layers was found to be rate determining step. The membrane was stable during the transport experiments. There is no leakage of carrier or nitrate ion-carrier complex to both aqueous phases and also, no supplementary water penetration into the membrane. This favours interfacial reaction of nitrate ion and carrier.List of symbols C a nitrate ion concentration in acceptor phase, (mol/l, M) C d nitrate ion concentration in donor phase, (mol/l, M) C m nitrate ion concentration in organic (membrane) phase, (mol/l, M) C d0 initial nitrate ion concentration in donor phase, (mol/l, M) k 1 membrane entrance rate constant, (min )1 ) k 2 membrane exit rate constant, (min )1 ) k 1d membrane entrance rate constant, (min )1 ) k 2a membrane exit rate constant, (min )1 ) k 2m membrane exit rate constant, (min )1 ) R a reduced nitrate concentration in acceptor phase, (dimensionless) R d reduced nitrate concentration in donor phase, (dimensionless) R m reduced nitrate concentration in organic (membrane) phase, (dimensionless) R m,max maximum reduced nitrate concen. in membrane phase, (dimensionless) R reduced nitrate ion concentration, (dimensionless) S dp/mem interface surface of donor phase over per unit of membrane, (cm 2 ) S ap/mem interface surface of acceptor phase over per unit of membrane, (cm 2 ) t time, (min) T max time which nitrate ions concentration becoming maximum, (min) T temperature, (°K) TOACl tetraoctyl ammonium chloride l i distance between phases, (cm) k wave length of UV spectrum e extinction coef®cient of UV spectrum x stirring speed (rev/min, rpm) x a stirring speed of acceptor phase (rev/min, rpm) x d stirring speed of donor phase (rev/min, rpm) x m stirring speed of organic (membrane) phase, (rev/min, rpm)

Kinetic Model for Solute Diffusion in Liquid Membrane Systems

“…By the comparison of the previous equation with equation (15), it can stated that total equilibrium is established when the equilibrium concentration of atropine dissolved in benzene in the first arm is equal to the concentration of atropine dissolved in benzene in the second arm. In other words, the operation will continue until the concentration of atropine dissolved in benzene is equal in both arms of the Utube.…”

“…In LMSs, the kinetic theoretical treatment is not as simple as most of its practical procedures because it includes many complex stages based on reversible, consecutive and diffusion phenomena. Many researchers describe the process as an ordinary consecutive mechanism for the material transport from the donor phase to the receptor phase through the membrane [15][16][17][18][19][20][21][22][23][24][25]. Others have merged Fick's second law of diffusion with the kinetics of reversible reactions [26][27][28], and some researchers have also described the process kinetics as first order mechanisms [29][30][31][32][33][34].…”

The Effect of Stirring Speed of Zinc Ions Transport Through Bulk Liquid Membrane Containing Di-2-ethylhexyl Phosphoric Acid (D2EHPA) in Kerosene

“…Ayırma sıvı filmde çözünme ve difüzyon farkından ileri gelmektedir (Noble and Way, 1989). Sıvı membranlar yüksek seçicilik, kolay kullanım, düşük maliyet ve taşınım veriminden dolayı uranyum (Zahakifar et al, 2018), bakır (Leon et al, 2016), nitrat (İrdemez et al, 2006), nitrit (Demircioğlu et al, 2000), p-nitrofenol (Pourkhanali et al, 2018), bizmut (Yamini et al, 2002), nikel (Yulizar et al, 2000) gibi ağır metal ve organik madde içeren sulu çözeltilerin arıtımında başarılı bir şekilde kullanılmaktadır.…”

“…Taşınım sitemlerinde hız sınırlayıcı aşama film tabakları içerisine çinko taşıyıcı komplekslerin difüzyonudur. Bu film tabakaların kalınlıkları da karıştırma hızı arttıkça azalmaktadır (Demircioğlu et al, 2000;Ma et al, 2001). Şekillerden de görüldüğü gibi karıştırma hız arttıkça çinko iyonlarının taşınım verimi artmaktadır.…”