Lignocellulosic Based Biochar Adsorbents for the Removal of Fluoride and Arsenic from Aqueous Solution: Isotherm and Kinetic Modeling.

Iram Ayaz,Basem H Elesawy,Abdul Qayyum,Khadiga Ahmed Ismail,Ahmad El Askary,Hajira Haroon,Naveed Ahmed,Jeffery Layton Ullman,Muhammad Rizwan,Amal F Gharib

doi:10.3390/polym14040715

Abstract

Eucalyptus wood is made up of lignocellulosic material; this lignocellulosic material contains two types of biopolymers, i.e., carbohydrate and aromatic polymers. In this study, this lignocellulosic material was used to prepare biochar. Three biochar, i.e., laboratory-based (B1), barrel-based (B2), and brick kiln-biochar (B3), were used for fluoride and arsenic removal from aqueous solution. Barrel-based biochar was prepared by using the two-barrel method’s alteration. The highest fluoride removal (99%) was attained at pH 2 in the presence of B1, while in the presence of B2 and B3, maximum fluoride removal was 90% and 45.7%, respectively. At pH 10, the maximum arsenic removal in the presence of B1, B2, and B3 was 96%, 94%, and 93%, respectively. The surface characteristics obtained by Fourier-transform infrared spectroscopy (FTIR) showed the presence of carbonyl group (C-O), and alkene (C=C) functional groups on all the three studied biochars. Isotherm studies showed that the adsorption was monolayered (all the adsorbed molecules were in contact with the surface layer of the adsorbent) as the Langmuir isotherm model best fits the obtained data. Adsorption kinetics was also performed. The R2 value supports the pseudo-second-order kinetics, which means that chemisorption was involved in adsorbing fluoride and arsenic. It is concluded that B1 gives maximum removal for both fluoride (99%) and arsenic (96%). The study shows that lignocellulose-based biochar can be used for arsenic and fluoride removal from water.

Highlights

The presence of toxic substances in drinking water can cause a risk to the human health [1,2]
These biochars were analyzed for their capability/potential for adsorbing both fluoride and arsenic from water
The highest fluoride removal was attained at pH 2, biochar-adsorbent dose of 0.1 g, and a contact time of 60 min in the case of both B1 and B2

Summary

Introduction

The presence of toxic substances in drinking water can cause a risk to the human health [1,2]. The study found the presence of arsenic, fluoride, and bacteria in drinking water [3]. Clean water is a fundamental human right, but pollution with metals, non-metals, natural processes, and some inorganic components such as fluoride and arsenic poses serious health problems. Arsenic is an element found in a natural setting, organisms, soil, and aquatic environment. Arsenic is among the prominent four nonessential elements: toxic arsenic, mercury, cadmium, and lead. It is considered the potential carcinogenic element [6]. According to the WHO, it is among group 1 human carcinogens [7]

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