The interaction of a naturally occurring membranous collagen with high-saline dye solutions – mechanistic features from unusual multi-step biosorption

Abstract

It is known that wastewaters containing dyes are very difficult to treat, since many dyes are stable and recalcitrant
molecules. In this way, sorption may suitable for effectively remove dyes in this specific application field.
In this work, a first approach for using polymeric membranous collagen of fish scales for sorption of saline
methylene blue dye (MB) solution found in subsurface procedures of oil well industry. From structural characterization,
the sorbent was found to be a composite of fibrillar type I collagen and apatites. The MB sorption
amounts decreased with temperature increasing, with maximum MB sorbed of 2.18 mmol g-1 at 25 0C. In most
sorption tests, residual MB in saline water was undetectable within 200 min of contact time. The sorption kinetic
data were well adjusted to a three-parameter multi-step exponential function. The good fitting of such function
were only obtained taking into account the presence of time-dependent kinetic parameters. The proposed multistep
sorption mechanism involved surface interaction and diffusion of MB into the membranous collagen. The
interaction of positively charged MB ions with the collagenous adsorbent occurred through electrostatic forces.
The results point out the collagenous adsorbent for effective procedures of sorption of MB dyes from high-saline
wastewaters.
Keywords: Biosorption; membranous adsorbents; high-saline water; multi-step kinetics; oil well.