Bio Adsorption: An Eco-friendly Alternative for Industrial Effluents Treatment 41

Aquatic systems are large bodies that receive many waste streams, mainly resulting from human

activities (Acumar 2019, Liu et al. 2008). The diversity of industries that may discharge their effluents

into a water body influences its degree and type of pollution. The assessment of the interferences that

may exist between various types of pollutants present simultaneously in a water body should keep

being studied as they may produce different effects on the ecosystem (Renaud et al. 2021). Prevention

is the way forward. Avoiding the discharge of effluents with high pollutant content is necessary and

finding systems that could selectively remove or decrease a specific pollutant concentration in the

presence of other substances is very promising regarding their recovery and reuse.

Due to their high persistence in the environment, metals have the potential to get bioaccumulated

in organisms of lower trophic levels and reach their biomagnification, with a direct implication

on the ecosystem and on the health of populations not directly exposed to contaminated water

(Di Giulio and Newman 2008). For these reasons, the Argentinian legislation considers them as

hazardous substances and regulates their content both in effluent discharges and in drinking and

irrigation waters (PLNRA 1992). However, this legislation as well as other water quality regulations

and guidelines in the world do not consider the effect of the simultaneous presence of different

metals (Renaud et al. 2021).

The search for low-cost processes for water treatment is fundamental to its applicability; waste

reuse is a possible path to follow. When thinking about the low cost of the process, this implies that

the waste should be sourced close to where it will be used in order to reduce transport expenses

as well as the carbon footprint of the process. It also implies making just a basic conditioning to

the waste, that is, treating the material as little as possible. Finally, the process must be adapted

to the specific effluent conditions, so as not to require adjustments involving the use of large

quantities of chemical reagents or energy. There are several established conventional processes for

pollutants treatment and recovery from wastewater (Mihelcic and Zimmerman 2012). However, in

recent years, studies on biosorption technologies development have increased due to their potential

economic convenience. Numerous works using lignocellulosic materials indicate a high capacity

to concentrate water pollutants in their structures (Boeykens et al. 2018, Boeykens et al. 2019, Piol

et al. 2021, Saralegui et al. 2021, Saralegui et al. 2022). For this work, wastes with high availability

in Argentina were selected: peanut shells (Arachis hypogaea), sugar cane bagasse (Saccharum

officinarum), avocado stones (Persea americana), pecan nut shells (Carya illinoinensis), wheat

bran (Triticum aestivum), banana shells (Mussa paradisiaca) and different parts of the moringa

plant (Moringa oleifera) for the study of metal removal from water.

Selected wastes:

• Peanut shells: Argentina is the sixth-largest producer of peanuts in the world, accounting

for 3% of global production, with 42.6 million tons produced during the 2016–2017 growing

season (Pellegrino 2019). Peanut shells, the waste from the industrialization of the nuts, are

often a drawback as they represent between a quarter and a fifth of the harvest and constitute a

polluting waste which is usually incinerated in the open air, generating large amounts of smoke

(BCC 2014).

• Sugar cane bagasse: another waste product is sugar cane bagasse, which is the fibrous

material that remains after the sugar cane is crushed. Typically, for every 10 tons of crushed

cane, 3 to 4 tons of wet bagasse (40–50% moisture) remains as residue. Increasingly, it is used

as fuel for steam and electricity generation in sugar mills, but also as a source of organic matter

when returned to the soil. According to statistics, in the last 10 yr’ harvest, 18 to 20 million

tons of sugar cane were milled in the country, producing a large volume of bagasse for disposal

(Preciado Patiño 2015, Rios et al. 2017).

• Avocado stone: the avocado stone represents about 18% of the fruit weight. In Argentina

it is currently a growing crop as different soils and climates are favorable for its growth and

development (Carrere 2010).