Phosphoric Acid Activation of Agricultural Residues and Bagasse from Sugar Cane:  Influence of the Experimental Conditions on Adsorption Characteristics of Activated Carbons

Abstract

Activated carbons from two different types of sugar cane wastes, agricultural residues and bagasse, were prepared by phosphoric acid activation varying the carbonization temperature (300-600 °C), the weight ratio of phosphoric acid to precursor (R ) 1-2.5), and carbonization time (0-3 h). Surface properties of the resulting carbons were markedly dependent on the precursor and a combined effect of the conditions employed. Bagasse carbons showed higher surface area and pore volume than those from agricultural residues. Maximum surface areas of around 1100 and 780 m 2 /g were respectively attained. Temperature above 500 °C, impregnation ratio higher than 2, or prolonged carbonization beyond 1 h led to reduction in porosity development. Selected carbons from both wastes with relatively large mean pore radius showed good ability to decolorize a diluted solution of synthetic melanoidin, used as a model of molasses wastewater. Iodine number between 608 and 746 and methylene blue uptake of 213-261 (mg/g) were determined for the selected samples.

Preparation and Characterization of Activated Carbon from Hydrochar by Phosphoric Acid Activation and its Adsorption Performance in Prehydrolysis Liquor

“…The results indicated that BET surface area and total pore volumes of activated carbon reached a maximum value of 2192 m 2 /g and 1.269 cm 3 /g for the activation time of 1 h. Then, the BET surface area and total pore volume decreased to 1615 m 2 /g and 0.95 cm 3 /g when the activation time was prolonged to 4 h. This could have been explained by the excessive time that led to the contraction and collapse of pores, thus the surface area and pore volume became smaller (Wang et al 2011). The effect of activation time on activated carbons was also reported by Castro et al (2000), that prolongation of activation time beyond 1 h led to a pronounced reduction in porosity development. …”

“…According to the Jagtoyen and Derbyshire (1998) study on the H3PO4 activation of hardwoods, the phosphate ester cross-linked structure forms and expands as the temperature rises in the lower temperature range of 200 °C to 450 °C, and then began to break down, causing contraction and a decrease in the surface area and pore volumes at higher temperatures above 450 °C. Similarly, Castro et al (2000) observed that the surface area and pore volumes were highly dependent on the temperature when using agricultural residues for activated carbon production.…”

“…2c). Also, a large number of small carbon pieces were accumulated together on the AC surface, which might have been caused by the combination of biopolymers fragments during carbonization process (Solum et al 1995;Castro et al 2000). Patnukao and Pavasant (2008) also observed the irregular structure of cracks and crevices on the AC surface when using phosphoric acid activation of Eucalyptus camaldulensis Dehnh.…”

“…This might have been caused by the change in the contact area between the hydrochar and phosphoric acid, which was affected by the impregnation ratio. The higher impregnation ratio would lead to the expansion of the pore structure, which initiated the collapse of the pores and structural contraction (Castro et al 2000;Sych et al 2012). Additionally, higher phosphate acid concentrations will form a protective layer to prevent the activating agent incorporating into the hydrochar, thus hindering any increases in specific surface area and total pore volume (Nahil and Williams 2012).…”

Preparação e caracterização de carvão ativado produzido a partir de resíduos do beneficiamento do café

“…Esse material se caracteriza quimicamente pelo seu alto teor de fibra bruta (celulose, lignina e hemicelulose) e baixos teores de extrativos e cinzas. 3 Em anos recentes, vários estudos relataram a produção de carvões ativados (CA) a partir de resíduos tais como sementes de frutas, 4 bagaço de cana-de-açúcar, 5 restos de couro, 6 pneus 7 etc. O carvão ativado (CA) é um material carbonáceo e poroso preparado pela carbonização e ativação de substâncias orgânicas, principalmente de origem vegetal.…”