Butanol

Production and characterization of activated carbon from Gorse (Ulex europaeus)

Milquez Harvey Andres a,*, Ceron Julian b, Calderon Andres b, Zuluaga L b.

aCentro de Investigación Científica de Yucatan. Mérida, Yucatán, México.

bFundación Universidad de América. Bogotá, Colombia.

Abstract

Gorse is one of the 100 most hazard invasive species of the world. In Colombia this plant was introduced as live fence and is disseminated by the Andes region. Affects water basins, native flora and fauna. The eradication actions were concentrated in manual and mechanical removal, whose wastes are incinerated or composting.

Besides, activated coal have a wide industrial application, especially in the water treatment, Colombia has an average annual consumption of 700 ton/year, with a price which varies between 0.5 and 3 USD/kg. Activation of carbonaceous raw material can be done via chemistry or physics, the chemical pathway requires the determination of the type of acid or base, concentration, temperature and time. The objective of this study is to produce activated carbon from gorse, identifying conditions for obtaining a commercial quality activated coal. The best conditions found were: 1) use of the stem of the plant, H3PO4 to 50% v/v, activation temperature 550 °C and time 0.52 h, to produce an activated coal macro porous type II with iodine value of 770.5 mg/g Coal, BET surface area 717.9 m2/g and apparent density 0.4655 g/ml.

Keywords 

Gorse, Ulex europaeus, activated coal, preparation, characterization.

1. Introduction

Gorse, also known as espinillo, retamo espinoso, argoma or tojo (Ulex europaeus) is a shrub of European origin, which is included in the list of the 100 most harmful invasive species of the world. Reports have been found in the America, Asia, Oceania and Africa [1]. 

It is a perennial plant, which grows by forming dense, impenetrable areas; it is extremely competitive, affects artificial and native plantations, capable of altering the conditions of the soil by be a nitrogen-fixing species, eradication is hard due to the prolonged viability of its seeds [2].

In Colombia, Gorse is located in the Andean region, mainly in the Departments of Antioquia, Cundinamarca and Boyaca, affecting water basins, native flora and fauna and becoming fuel for forest fires [3].

Colombian legislation prohibits planting, transplanting, sale, distribution and marketing of Gorse, by causing various environmental and social problems related to water, fire and drought [4], [5] and [6].

Different governmental sectors have made actions, with the purpose to eradicate the specie, which include: composting [7], planting of native species [1], manual removal, mechanical removal, chemical control, biological control, grazing and controlled fires [8] c.

Activated carbon is a material of porous structure, which gives high adsorption capacity [11]. Its applications include water purification, removal of organic and/or toxic compounds, elimination of color and scent and basis of catalysts [12].

Activation of the coal requires two primary elements, the source of carbon and the activation method. The method of activation can be chemical or physical [13].

Chemical activation consists in increase temperature between 500 -- 700 ºC in an oxygen-free environment, raw material is smeared with chemical agents (phosphoric acid, sulfuric acid or zinc chloride). Physical activation starts with the charring of the raw material, where hydrogen and oxygen are deleted, and continues with the activation with water vapor, air or CO2, at temperatures between 700 and 1100 ºC [14].

Preparation of activated carbon using alternative raw materials is an area of different studies, agro-industrial waste [15],  [16], [17], [18], [19], [20], [21], [22], forest species [23], [24], [25], activated sludge [26], [27], among other sources.

The objective of this study is evaluate the use of Gorse (Ulex europaeus), as a raw material for the preparation of activated carbon through a chemical process.

2. Materials and Methods

Gorse was collected in the foothills of Monserrate, located in the eastern part of Bogota, Colombia. The plant is dug up to release the roots, taking great care before depositing it in bags without spreading seeds.

The project was divided into two phases, first the variables analyzed were: part of the shrub (group 1 [G1]: leaves, seeds and fruits, group 2 [G2]: stems) and concentration of phosphoric acid (50 - 67.5 and 85% v/v), the schema used is shown in table 1. 

Table 1. Phase 1 experimental conditions.

For second phase, best result of the first was maintained constant, temperature was changed (between 382 and 718 ºC) and activation time (between 0.52 and 2.68 h), using a orthogonal central composite experimental design, the design shown in figure 1 where the first coordinate is the temperature ( °C) and the second time (h).

Figure 1. Orthogonal central surface design

Raw material collected was sun dried for 24 hours, to the stalks were reduced its size to facilitate processing by using a carbon disk of 40 teeth.

Material was processed in a disc mill and sieve until have precursor diameter between 5 and 10 mm diameter. After was impregnating with H3PO4, there were two drying processes, the first 110 ºC for 1 h and second 150 ºC for 1.5 h. Once dry the material, the activation was performed.

The activation was made in a 3 L reactor, with maximum temperature of 1000 ºC, type K thermocouple, wool as insulating and coated with sand, two ports for input and output of nitrogen, in order to complete the product was washed with distilled water to ensure a neutral pH.

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