Production and Characterization of Activated Carbon from Coal for Gold Adsorption in Cyanide Solutions

Abstract

In this work, activated carbons were produced using coal as raw matter from seven Colombian carboniferous zones. Physical activation was performed in two stages: a carbonization stage with Nitrogen at a temperature of 850 °C and a residence time of 2 h, followed by an activation stage using steam at temperatures of 700 and 850 °C with residence times of 1.5 h and 2.5 h. From the pore volume characterization for the adsorption of gold, two activated carbons from Cundinamarca, obtained at 850 °C (1.5 h), 850 °C (2.5 h), and a commercial carbon (GRC 22) were selected. Gold adsorption tests were performed with those three activated carbons using synthetic aurocyanide solutions and a gold waste solution. The data of the adsorption isotherms were adjusted using the Freundlich adsorption model for the synthetic solution, as well as Langmuir for the waste solution. The results showed that, using a solution of 1 ppm, the activated carbons C-850-2.5 and C- 850-1.5 produced the higher maximum gold loading capacities in the equilibrium (8.7 and 9.3 mg Au/g, respectively) in comparison to the commercial activated carbon (4.7 mg Au/g). Gold adsorption test using a waste solution (21 ppm of gold) showed that the activated carbon C-850-1.5 had the highest value of adsorption capacity (4.58 mg Au/g) compared to C-850-2.5 (2.95 mgAu /g).

Adsorption Thermodynamics of Cr(VI) Removal by using Agro-Industrial Waste of Oil Palm Bagasse and Plantain Peels

“…For the plantain peel, a cylindrical aspect is observed. In contrast, an entanglement structure with porosity is noted for the palm bagasse, typical of lignocellulosic materials (Martínez-Mendoza et al, 2020). This characteristic is extremely beneficial for metal ion transport which increases the adsorption capacity (Pradhan, Arora, and Mahajani, 2018).…”

Hydrochars produced by hydrothermal carbonisation of seaweed, coconut shell and oak: effect of processing temperature on physicochemical adsorbent characteristics

“…At high temperatures, the oxygen containing surface compounds were consumed more easily. As reported by Martinez-Mendoza et al [70], this generates spaces in the structure through which fixed carbon is consumed allowing the widening of the pores. This is because intramolecular dehydration reactions [71] followed by decarboxylation reactions take place in the solid-to-solid conversion pathway [72].…”

“…HTC resulted in an increase in the fixed carbon content and the levels in the hydrochars increased with a rise in the HTC temperature. Martinez-Mendoza et al [70] found that fixed carbon and volatile matter suggest the extent of carbonisation and relate to porosity development in the hydrochars, while an additional activation stage consumes fixed carbon from the char walls, causing them to widen. However, there was no activation process in this present study.…”

“…The very high increased in the ash content of the Oak-HC250 may be due to the precipitation of inorganic salts on the hydrochar during HTC at higher temperature [77], which correlated with the higher yield of the Oak-HC250 hydrochar (Table 1), caused by polymerisation reactions leading to continues reaction of the lignin intermediates to char [38]. High levels of ash content are undesirable as it blocks the micropores (< 10 nm), creating inactive sites [70], and reducing the mechanical properties of the adsorbents.…”

Production of Activated Carbon From Rice Husk and Its Proximate Analysis

“…Figure 5: (a) SEM of rice husk; (b) SEM of rice husk char; c) SEM of activated carbon(Hanum et al, 2017) Hidayu, et al (2013). produced activated carbon from oil palm empty fruit bunches and activated with superheated steam at 765 o C for 77 min Martínez-Mendoza, et al (2020). produced activated carbon from Bituminous and subbituminous coal in two stages.…”