Humulus scandens-Derived Biochars for the Effective Removal of Heavy Metal Ions: Isotherm/Kinetic Study, Column Adsorption and Mechanism Investigation.

Xingang Bai,Dapeng Wu,Kexin Huang,Mengmeng Yin,Ning Liu,Nana Ma,Luyang Xing,Kai Jiang

doi:10.3390/nano11123255

Abstract

Humulus scandens was first adopted as a biomass precursor to prepare biochars by means of a facile molten salt method. The optimized biochar exhibits a high specific surface area of ~450 m2/g, a rich porous structure and abundant oxygen functional groups, which demonstrate excellent adsorption performance for heavy metal ions. The isotherm curves fit well with the Langmuir models, indicating that the process is governed by the chemical adsorption, and that the maximum adsorption capacity can reach 748 and 221 mg/g for Pb2+ and Cu2+, respectively. In addition, the optimized biochar demonstrates good anti-interference ability and outstanding removal efficiency for Cu2+ and Pb2+ in simulated wastewater. The mechanism investigation and DFT calculation suggest that the oxygen functional groups play dominant roles in the adsorption process by enhancing the binding energy towards the heavy metal ions. Meanwhile, ion exchange also serves as the main reason for the effective removal.

Highlights

A large number of studies have proven that the outstanding adsorption performance of biochar originates from the large surface area, stable porous structure, abundant surface oxygen functional groups such as carboxyl and hydroxyl groups, and rich mineral species which can remove the harmful ions through the ion exchange process [13]
Of weight loss ends around ~170 ◦ C, which corresponds to the evaporation of moisture and decomposition of organic matter in Humulus scandens (HS)
(310.6 and 110.0 mg/g for Pb2+ and Cu2+ ). These results further indicate that under the conditions of an air atmosphere and high temperature, the etching effects of molten salt and NaOH on carbon products can endow the biochar with high specific surface area and rich oxygen functional groups, which is conducive to the adsorption capacity of heavy metal ions

Summary

Introduction

Harmful heavy metal ions such as cadmium, chromium, lead, arsenic, copper, mercury and so on are commonly detected in different water bodies [5,6]. Chemical, physical and biological methods including electrochemical treatment, ion exchange, chemical precipitation and adsorption are the mostly commonly employed strategies to remove heavy metal ions from wastewater [7]. Among these methods, adsorption is considered an effective and economic method because of its facile operation and low cost [8,9]. It is of great significance to develop high-efficiency and low-cost biochar materials to remove heavy metals from polluted water environments [14]

Methods

Results

Conclusion