Adsorption of Ammonium Nitrogen from Aqueous Solution on Chemically Activated Biochar Prepared from Sorghum Distillers Grain

Derlin Hsu,Changyi Lu,Tairan Pang,Yuanpeng Wang,Guanhua Wang

doi:10.3390/app9235249

Derlin Hsu, Changyi Lu + Show 3 more

Open Access

https://doi.org/10.3390/app9235249

Copy DOI

Abstract

Chemically activated biochars prepared from sorghum distillers grain using two base activators (NaOH and KOH) were investigated for their adsorption properties with respect to ammonium nitrogen from aqueous solution. Detailed characterizations, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and specific surface area analyses, were carried out to offer a broad evaluation of the prepared biochars. The results showed that the NaOH- and KOH-activated biochars exhibited significantly enhanced adsorption capacity, by 2.93 and 4.74 times, respectively, in comparison with the pristine biochar. Although the NaOH-activated biochar possessed larger specific surface area (132.8 and 117.7 m2/g for the NaOH- and KOH-activated biochars, respectively), the KOH-activated biochar had higher adsorption capacity owing to its much higher content of functional groups. The adsorption kinetics and isotherms of the KOH-activated biochar at different temperatures were further studied. The biochar had a maximum adsorption capacity of 14.34 mg/g at 45 °C, which was satisfactory compared with other biochars prepared using different feedstocks. The adsorption process followed pseudo-second-order kinetics, and chemical adsorption was the rate-controlling step. The equilibrium data were consistent with the Freundlich isotherm, and the thermodynamic parameters suggested that the adsorption process was endothermic and spontaneous. Consequently, this work demonstrates that chemically activated biochar from sorghum distillers grain is effective for ammonium nitrogen removal.

Highlights

Water pollution has become a major concern, and water pollution control has been regarded as a priority for both society and public authorities [1]
The elemental analysis suggested that the Sorghum distillers grain (SDG) mainly contained C (44.1%), H (6.5%), and N (2.9%) because of its high starch, cellulose, and protein contents
The pseudo-second-order kinetics model had higher correlation coefficient values (R2 ) than the pseudo-first-order model (Table 1). These results suggest that the adsorption of the NH4 + -N on KOH-activated biochar followed a pseudo-second-order kinetics model

Summary

Introduction

Water pollution has become a major concern, and water pollution control has been regarded as a priority for both society and public authorities [1]. The chemical compositions of natural water resources are primarily determined by industrial, domestic, and agricultural practices, geology, climate, and other natural and anthropic sources [2]. The anthropogenic pollutants, such as nitrogen compounds, metals, pesticides, pharmaceuticals, personal care products, etc., have a critical effect on the quality of water resources [3]. Ammonium nitrogen is a common water contaminant and is generally released into the environment through industrial effluent and agricultural drainage [4]. Excess ammonium nitrogen in water leads to a series of ecological problems in aquatic environments.

Methods

Results

Conclusion