Enhanced transport of Lignosulfonate by integrating adsorption sweep in a liquid membrane module

摘要

Carrier mediated liquid membrane (LM) processes are unique in a way where proper selection of a carrier can achieve complete separation of the targeted species. This aspect is particularly important in multi-component systems. However, resistance to transport across the membrane phase and low concentration gradient across the LM-strip interphase restricts the overall transport performance. This article proposes an improvised method in a LM transport by integrating adsorption sweep. The investigated species was Lignosulfonate (LS) and the preferred adsorbent was MIL-101 (Cr) metal organic framework (MOF). Pure adsorption study showed high affinity of MIL-101 (Cr) for LS with ca. 94% removal from its model solution. Langmuir isotherm best fits the equilibrium data and pseudo second order model best explains the kinetics. Adsorption sweep experiments showed an overall improvement in extraction percentage of LS from 92% (regular bulk liquid membrane study) to ca. 97%. The recovery percentage of LS was decreased from ca. 75% (regular bulk liquid membrane study) to 10% because of adsorption of LS from bulk stripping medium, leading to an increase in concentration gradient across LM-strip interphase. Favorable chemistry of the stripping medium was found to be important for maintaining suitable pH conditions for the success of adsorption sweep process. During LS transport this aspect was clearly observed when the pH of the stripping medium got reduced, owing to the formation of H2SO4, the resulting adsorption sweep was more pronounced.