Effects of NaOH Activation on Adsorptive Removal of Herbicides by Biochars Prepared from Ground Coffee Residues

Yong-Gu Lee,Changgil Son,Jinwoo Kwak,Kangmin Chon,Sangwon Kim,Kyung Hwa Cho,Jaegwan Shin

doi:10.3390/en14051297

Abstract

In this study, the adsorption of herbicides using ground coffee residue biochars without (GCRB) and with NaOH activation (GCRB-N) was compared to provide deeper insights into their adsorption behaviors and mechanisms. The physicochemical characteristics of GCRB and GCRB-N were analyzed using Brunauer–Emmett–Teller surface area, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the effects of pH, temperature, ionic strength, and humic acids on the adsorption of herbicides were identified. Moreover, the adsorption kinetics and isotherms were studied. The specific surface area and total pore volume of GCRB-N (405.33 m2/g and 0.293 cm3/g) were greater than those of GCRB (3.83 m2/g and 0.014 cm3/g). The GCBR-N could more effectively remove the herbicides (Qe,exp of Alachlor = 122.71 μmol/g, Qe,exp of Diuron = 166.42 μmol/g, and Qe,exp of Simazine = 99.16 μmol/g) than GCRB (Qe,exp of Alachlor = 11.74 μmol/g, Qe,exp of Diuron = 9.95 μmol/g, and Qe,exp of Simazine = 6.53 μmol/g). These results suggested that chemical activation with NaOH might be a promising option to make the GCRB more practical and effective for removing herbicides in the aqueous solutions.

Highlights

The increasing use of herbicides with different action modes to enhance agricultural production can lead to non-point source pollutants of surface water and groundwater through herbicides leaching and runoff from agricultural fields [1,2,3]
These results demonstrated that the aromaticity (H/C = 0.022 of the ground coffee residue biochars without (GCRB) and H/C = 0.017 of the GCRB-N) and polarity ((O+N)/C = 0.085 of the GCRB and (O+N)/C = 0.060 of the GCRB-N) of the GCRB were found to increase due to NaOH activation
This study investigated the effects of the NaOH activation on the physicochemical characteristics of GCRB related to the adsorptions of the herbicides (ALA, DIU, and SIM)

Summary

Introduction

The increasing use of herbicides with different action modes (e.g., photosynthesis inhibition, plant growth regulation) to enhance agricultural production can lead to non-point source pollutants of surface water and groundwater through herbicides leaching and runoff from agricultural fields [1,2,3]. Simazine (SIM), chlorotriazine herbicide, has been extensively used since the 1950s for selective weed control, it can generate mutagenicity, reproductive and immune toxicities on the fish and amphibians due to low biodegradation rate and high ecological toxicity [9,10,11]. Based on these reasons, wastewater treatment techniques have achieved significant importance as increasing attention to global environmental concerns for herbicide pollution of the water sources

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