Modified Spruce Sawdust for Sorption of Hexavalent Chromium in Batch Systems and Fixed-Bed Columns.

Dororthea Politi,Dimitrios Sidiras

doi:10.3390/molecules25215156

Abstract

This study investigated the potential use of spruce sawdust that was pretreated with diethylene glycol and sulfuric acid for the removal of hexavalent chromium from wastewater. The sawdust pretreatment process was conducted at different temperatures and times. The adsorbent was characterized by quantitative saccharification, scanning electron microscopy, and Brunauer–Emmet–Teller surface area analysis. Adsorption capacity was studied for both batch and column processes. The experimental adsorption isotherms were simulated using seven isotherm models, including Freundlich and Langmuir models. By using the Langmuir isotherm model, the maximal Cr(VI) adsorption capacity of organosolv-pretreated spruce sawdust (qm) was 318.3 mg g−1. Furthermore, the kinetic data were fitted to Lagergren, pseudo-second-order, and intraparticle diffusion models, revealing that the adsorption of Cr(VI) onto spruce sawdust pretreated with diethylene glycol and sulfuric acid is best represented by the pseudo-second-order kinetic model. Three kinetic models, namely, the Bohart–Adams model, Thomas model, and modified dose–response (MDR) model, were used to fit the experimental data obtained from the column experiments and to resolve the characteristic parameters. The Thomas adsorption column capacity of the sawdust was increased from 2.44 to 31.1 mg g−1 upon pretreatment, thus, demonstrating that organosolv treatment enhances the adsorption capability of the material.

Highlights

The increased magnitude of industrial processes has led to overwhelming environmental pollution and enormous damage to specific ecosystems
The use of chromium is worrying because it is being increasingly utilized in developing countries in a number of industries, such as leather tanning, electroplating, textile dyeing, and metal finishing [2]
The material pretreated with organic solvent and acid catalyst

Summary

Introduction

The increased magnitude of industrial processes has led to overwhelming environmental pollution and enormous damage to specific ecosystems. The high toxicity of heavy metals makes them significant environmental and public health threats. Heavy metals speak to a significant issue for the environment and for all the life forms, since they are not biodegradable and can gather in living tissues, reaching human organisms as well through the chain food [1]. The use of chromium is worrying because it is being increasingly utilized in developing countries in a number of industries, such as leather tanning, electroplating, textile dyeing, and metal finishing [2]. A number of countries are facing issues in relation to the presence of hexavalent chromium in natural ecosystems. It was recently discovered that the Asopos and Thiva Basins are massively contaminated with Cr(VI) because of the excessive industrial activity around the area and unregulated discharge even though a Cr(VI) limit in industrial discharge is mandatory to acquire licensing [5]

Methods

Results

Conclusion