3. Orange peels

Orange peels are waste generated mainly by the juicing industry that can cause environmental problems due to its large volume of generation and physicochemical characteristics, such as soil and water pollution. For this reason, the recovery and transformation of orange peels has become a topic of interest for recent investigations; one important alternative is the preparation of sorbent materials.

4. Sorbent materials obtained from orange peels

Table 3. Physicochemical composition of the orange peel [7].

1

2

g of citric acid/100 mL.

db = dry basis.

dioxide (basis of physical activation) [13].

The elaboration of high-quality sorbent materials from agroindustrial waste opens an effective

Activated carbons are commonly used as sorbent materials due to their sorption capacity; those activated carbons are produced from a wide variety of carbon-based materials. Those materials used for the production of activated carbon are carbon-based organic materials, such as coal, lignite, and wood. Although natural coal is the most used precursor, agroindustrial waste is considered as a good alternative; in this way, the activated carbon produced from waste would reduce the demand of forests since wood is also used for this purpose [12].

According to International Union of Pure and Applied Chemistry (IUPAC), an activated carbon is a porous carbonaceous material that has been subjected to gas reaction, sometimes with chemical agents, during or after carbonization process in order to increase its sorption properties. The use of carbon-based materials goes so far back in history, since charred wood and mineral coal or simply partially volatilized coal materials were already used for similar purposes.

From 1901, several patented methods of activated carbon production were registered. In this way, R. Von Ostrejko patented two methods to produce activated carbon: one based on the carbonization of lignocellulosic materials with metal chlorides (the basis of chemical activation) and the second method based on a gentle gasification of coals with water vapor or carbon

path for the conversion of these residues into high value added products [11].

Parameter Value Soluble solids (Brix) 7.10 1.2 pH 3.93 0.003 Acidity<sup>1</sup> 0.29 0.003 Formaldehyde 34.00 2.4 Moisture (%) 60.5 Ash (%)2 3.29 0.19 Fat content (%)<sup>2</sup> 0.2 Protein (%)2 1.5

Sustainable Sorbent Materials Obtained from Orange Peel as an Alternative for Water Treatment

http://dx.doi.org/10.5772/intechopen.76137

205

Carbohydrates (%)<sup>2</sup> 89.00 1.1 Pectin (%)<sup>2</sup> 170.00 <sup>5</sup> Lignin 3.20 0.4 Essential oils (mL/kg) 1.45 0.16

The waste material of the orange industry is constituted mainly by peels, shells, seeds, and capillary membranes. When leaving the industry, the orange peels have a high level of organic matter and low pH; such indicators demonstrate the potential polluting. Since the composition of orange peels can be transformed to use as raw material for the production of national interest products, in this way, value-added products can be obtained due to the valorization process, and, at the same time, it is possible to reduce the environmental impact [5, 6].

#### 3.1. Physicochemical composition of orange peel

The chemical composition of orange peels, shown in Table 3, makes them an attractive source of industrial products. Soluble sugars present in orange peels are composed mostly of sucrose, glucose, and fructose, while organic acids are composed of citric, oxalic, and succinic acid. The fiber is the portion of the shell where the pectin is contained. The pectins contained in the orange fiber are soluble and insoluble in the form of protopectin [5].

However, resent investigations of citrus waste focus on the recovery of a single component, such as d-limonene, pectin, or bioethanol [8].

Recent investigations have shown that orange peel is a potentially valuable resource that can be transformed into value-added products; the most common alternatives have reported the use of this material as livestock feed, source of heat generation, biomethanization, and compost [9, 10].


2 db = dry basis.

The oranges processed in the industry are destined in its majority to the juice export market (Table 2). Studies show that Mexico, in comparison with large producing countries, has been increasing the amount of juice produced over the years. Mexico has had a great inclusion in the international market, satisfying the demand of countries such as the United States, Canada,

Production 2011 2012 2013 2014 2015 2016 Mexico 2011 2012 2013 2014 2015 2016 EUA 79 143 121 153 158 163 Brazil 110 114 113 81 66 65

Table 2. Export data of orange juice, considering 1000 metric tons at 65 BRIX.

Orange peels are waste generated mainly by the juicing industry that can cause environmental problems due to its large volume of generation and physicochemical characteristics, such as soil and water pollution. For this reason, the recovery and transformation of orange peels has become a topic of interest for recent investigations; one important alternative is the preparation

The waste material of the orange industry is constituted mainly by peels, shells, seeds, and capillary membranes. When leaving the industry, the orange peels have a high level of organic matter and low pH; such indicators demonstrate the potential polluting. Since the composition of orange peels can be transformed to use as raw material for the production of national interest products, in this way, value-added products can be obtained due to the valorization

The chemical composition of orange peels, shown in Table 3, makes them an attractive source of industrial products. Soluble sugars present in orange peels are composed mostly of sucrose, glucose, and fructose, while organic acids are composed of citric, oxalic, and succinic acid. The fiber is the portion of the shell where the pectin is contained. The pectins contained in the

However, resent investigations of citrus waste focus on the recovery of a single component,

Recent investigations have shown that orange peel is a potentially valuable resource that can be transformed into value-added products; the most common alternatives have reported the use of this material as livestock feed, source of heat generation, biomethanization, and com-

process, and, at the same time, it is possible to reduce the environmental impact [5, 6].

3.1. Physicochemical composition of orange peel

such as d-limonene, pectin, or bioethanol [8].

orange fiber are soluble and insoluble in the form of protopectin [5].

and Japan, among others [3, 4].

204 Wastewater and Water Quality

3. Orange peels

of sorbent materials.

post [9, 10].

Table 3. Physicochemical composition of the orange peel [7].
