Global Journal of Engineering Sciences (GJES)
A
Short Analysis of Biosorbents and its Potential Removal Contaminants from
Aqueous Media
Authored by Guilherme L Dotto
Abstract
Biosorbents are
materials applied in the sorption process, and are extensively studied
throughout the years. Here a brief discussion about the origin of each common
biosorbent studied and major characteristics are presented.
Keywords: Characteristics;
Biosorbent; Dyes; Heavy metal; Pesticides; Pharmaceuticals
Introduction
The development of
industrial activities led to an increase in the volume of industrial effluents
generated. These effluents present a wide variety of organic and inorganic
pollutants, such as dyes, heavy metals, pesticides, pharmaceuticals, and aromatic
molecules [1–4]. The release of untreated effluents causes serious
environmental damage and further public health risk [5].There are several
methods for treating these effluents. Some examples are oxidation,
electrolysis, ozonation, filtration, reverse osmosis, flocculation/
coagulation, biosorption, microorganisms, and enzymes. Among these techniques,
the biosorption is one of the most studied alternatives in the last years,
mainly due to its economic aspects and practical application. The biosorption
terminology consists of the union of the “bio” prefix and the “sorption”
suffix. From a technical point of view mean the application of the adsorption
method using materials from biological bias, often called biosorbents.
Biosorbents
Characteristics and Classification
The biosorbent needs to
present several characteristics to ensure further employment. The first
characteristic is the low-cost and availability, taking into consideration the
transport and any modification of the material. To be further applied, the
biosorbent need to present chemical and mechanical stability, in special for
continuous systems. Significant physicochemical and textural proprieties, in
other words, high surface area, pore-volume, and functional groups. These
characteristics increase the chances of the higher concentration gradient
between the bulk phase and the biosorbent [6]. Although all these
characteristics are important for the biosorbent applications, it is difficult
to develop a biosorbent with all these features.
The biosorbents
present economic and sustainable benefits. These characteristics have drawn the
attention to biosorption studies, where the number of publications doubled in a
decade (Figure 1). These studies show several biosorbents developed with
different species in the removal of dyes, drugs, pesticides, metals, among
others. The latest published articles still bring new materials both in natural
and modified to remove pollutants. Still, the lack of fixed-bed biosorption
publications is a major concern.
Figure 2 presents the
classification for the biosorbents, which is further detailed. The tree bark
has been applied for the adsorption of different dyes, such as crystal violet
and red 97 [7,8]. The biosorbent from threes often present good biosorption capacity
and mechanical stability. Nevertheless, depending on the species, the higher
presence of lignin results in lower adsorption capacity. The fruit’s seeds are
often applied as biosorbents as well for the removal of dyes and heavy metals
(Pb, Cd, and Zn) [9,10].In some cases, the fruits seed present low adsorption
performance, due to the presence of oil in the composition. Thus further
treatment is welcome. Another material that can be obtained from the wood and
agricultural industry is the leaves, for the biosorption of dyes to
pharmaceuticals [11]. Generally, the leaves are modified using basic or acid
solutions, or used for preparing activated carbon. Other biosorbents are made
from the agro-industrial residues are husk and process wastes. Some works have
reported the application of activated carbon from rice husk for the removal of
ciprofloxacin [12]. Sugar cane and cassava have been modified for the removal
of methylene blue [13]. The fruit peel is another often studied, biosorbent
group. Similarly, the biosorbent is modified and present low mechanical
resistance From the shrimp industry wastes, chitin and chitosan are obtained.
These materials are excellent biosorbents, being applied for the removal of
dyes, metals, pesticides, pharmaceuticals, and many other compounds [6].
However, chitin and chitosan, similar to other materials, present low
mechanical stability. This downside has led to the development of advanced
materials such as films, sponge, nanowhiskers, nanoparticles, and nanofibers.
Last, the fungi biomass has been reported on the literature as well, e.g., the
Bacillus licheniformis was used for the removal of lead [14]. The mainly
challenged involving the fungi biomass is related to the fungi production
process, which demands time for growth stage.
Conclusion
In this mini-review, the biosorbent state of the art was presented shortly. The first aspect is that the development of biosorbents has exponentially increased over the years. These materials present a variated biosorption capacity, according to nature and origin. The major characteristics of the biosorbent are related to sustainable and economic characteristics. However, the lack of fixed-bed biosorption reports is a major flaw. Also, the works are mainly focused on the removal of one pollutant per operation. It should be considered the application for mixtures of pollutants to approach real-life effluent conditions.
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