Comparative Study on the Efficiency of Mercury Removal From Wastewater Using Bacterial Cellulose Membranes and Their Oxidized Analogue.

D Suárez-Avendaño,E Martínez-Correa,P Gañán-Rojo,M Peresin,A Cañas-Gutierrez,M Castro-Riascos,M Pereira,C Castro-Herazo,R Zuluaga-Gallego

doi:10.3389/fbioe.2022.815892

Abstract

A comparative study was conducted on the efficiency of mercury removal using bacterial nanocellulose (BNC) membranes obtained from the fermentation of the microorganism Komagataeibacter medellinensis, in contrast with its oxidized analog obtained by modifying the bacterial nanocellulose membranes via oxidation with 2,2,6,6-Tetramethylpiperidine-1-oxyl. Both types of membranes (modified and unmodified) were characterized to identify variations in the Physico-chemical parameters after modification. FTIR spectra confirmed the chemical modification of cellulose in all reaction conditions by the presence of a new characteristic band at ∼1730 cm−1, corresponding to the new carboxylic groups produced by the oxidative process, and the decline of the band at ∼1,650 cm−1, corresponding to the hydroxyl groups of the C6 carbon. While the XRD profiles indicated that the percentage of BNC crystallinity decreased and the SEM images showed that the nanoribbon network was interrupted as the amount of oxidizing agent increased. The kinetics of mercury removal from both types of membrane was evaluated by calculating the concentration of mercury at different times and establishing a mathematical model to describe the kinetics of this process. The modified membranes improved significantly the adsorption process of the metal ion and it was found that the modification that results in the greatest adsorption efficiency was BNC-m 7.5 with a value of 92.97%. The results obtained suggest that the modification of the bacterial nanocellulose membranes by oxidation transcendentally improves the mercury removal capacity, outlining the modified membranes as an excellent material for mercury removal in wastewater.

Highlights

The population growth leads to an increase in the industrial production of goods, many of these use raw materials obtained from mining activities
The pseudo-second-order model considers that the speed is directly proportional to the number of active sites on the surface of the adsorbent and the number of metal ions adsorbed onto the surface in time t and equilibrium (Renuka R and K 2013), which indicates that the adsorption process between the adsorbent and the mercury ions occurs through chemical interactions, which implies a process of chemisorption on the surface of the bacterial nanocellulose (BNC) and Bacterial nanocellulose membranes were modified (BNC-m) membranes
Bacterial nanocellulose membranes were modified using an oxidative process mediated by TEMPO

Summary

Introduction

The population growth leads to an increase in the industrial production of goods, many of these use raw materials obtained from mining activities. Wastewater contaminated with heavy metals is released directly or indirectly into the environment each day, which is a huge problem due to the persistence of these pollutants in nature (Fu and Wang 2011; Yu et al, 2013a; Hokkanen 2014). In Colombia, there is evidence of environmental pollution in water sources and the air by mercury, and there have been reports of its presence in birds and humans in areas of high influence mining, such as Bajo Cauca and the north of Antioquia (Olivero et al, 1995; Olivero V and Jhonson R 2002; Olivero-Verbel et al, 2006). The contamination resulting from human economic activities may arise from waste discharge, direct emissions into the atmosphere from the burning of fossil fuels, incineration of solid waste and smelting of metals such as copper and zinc (Olivero V and Jhonson R 2002)

Methods

Results

Conclusion