Trypan blue removal from water with zein sorbents and laccase

Tatianna Marshall,Alejandro G Marangoni,Xiuju Wang,Erica Pensini,Loong-Tak Lim,Kristine Lamont

doi:10.1007/s42452-020-04107-w

Abstract

Zein-based materials were used to remove Trypan blue from water under flow conditions and in batch tests. In flow tests, zein dissolved at pH = 13 was injected in sand columns and subsequently coagulated with CaCl2, to create an adsorbent filter which removed over 99% of Trypan blue. Batch tests were conducted using zein powder, zein dissolved at pH = 13 and coagulated with CaCl2, Fe2Cl3 or citric acid, and zein dissolved in ethanol and then coagulated with water. The highest Trypan blue removal was achieved with zein powder (4000 mg Trypan blue/kg sorbent, as determined through spectrophotometry), followed by zein coagulated with Fe2Cl3 (500 mg Trypan blue/kg sorbent) and with other salts (140 mg Trypan blue/kg sorbent). Differences in the sorption efficiency are attributed to differences in the surface area. The sorption isotherm of Trypan blue onto zein-based sorbents was a Type II isotherm, suggesting physisorption. Desorption of Trypan blue was limited when zein-based coagulated sorbents were immersed in pure water. Trypan blue could be degraded by free laccase in water, as determined through spectrophotometry and electrospray ionization mass spectroscopy (ESI-MS). Trypan blue could also be degraded by laccase when zein-based laccase-containing sorbents were prepared at pH = 10, using Fe2Cl3 as coagulant.Graphic abstract

Highlights

Pollution from industrial processes has recently become a significant worldwide concern [1]
Removal efficiencies of zein sorbents in sorbing Trypan blue from water in batch tests conducted under quiescent conditions over 24 h were determined using spectrophotometry and a calibration curve
Sorption was most significant with zein powder, likely due to its high surface area compared to zein-based sorbents coagulated with CaCl2, Fe2Cl3 or citric acid, or obtained by adding water to zein solutions in ethanol (Figure 2)

Summary

Introduction

Pollution from industrial processes has recently become a significant worldwide concern [1]. Dyes are used in the textile industry [2] and in other industries [3], including paper printing, color photography, pharmaceutical, food, cosmetic, and leather industries [4]. Despite their widespread use, dyes are toxic to humans and to the environment. Trypan blue is a teratogen [8], and it can harm the human eye [9] In addition to their toxicity, when dyes are released in water bodies, they reduce light penetration in water, and they prevent oxygen ingress and increase biochemical oxygen demand [4]. Azo dyes represent approximately half of all dyes used, and they are the largest group of synthetic colorants released into the environment [4]

Methods

Results

Conclusion