J. Chem. Tech. Biotechnol. 1982,32, zyxwvu 575-579 zyxwvuts Effect of Carbon-Oxygen and Carbon-Sulphur Surface Complexes on the Adsorption of Mercuric Chloride in Aqueous Solutions by Activated Carbons zyx Juan de Dios Lopez-Gonzalez", Carlos Moreno-Castilla, Antonio Guerrero-Ruiz and Francisco Rodriguez-Reinoso6 Departamento de Quimica lnorgrinica, Facultad de Ciencias, Granada, Spain (Paper received zyxwvutsr 1 February 1982 and accepted 6 March 1982) Several activated carbons obtained from commercial sources have been tested for their ability to remove mercuric chloride (HgC12) from aqueous solutions. The chemical nature of the surface of the activated carbons was changed by introducing carbon-oxygen and carbon-sulphur surface complexes. The influence of these types of complexes on the adsorption of HgClz by the activated carbons has been studied. It seems that the existence of hydroquinonic, phenolic and hydrosulphide groups on the surface of the carbon reduces Hg(I1) to Hg(1). However, there was an increase in the adsorption of Hg(1l) when sulphide or hydrosulphide groups were present on the surface of the carbon. The effect of the pH of the solutions on HgCl2 adsorption was also studied; when the pH was changed from 1 to 7 there was an enhancement of the adsorption of HgClz by the activated carbons. 1. Introduction Activated carbons exhibit a great potential as adsorbents for the treatment of waste and surface waters. They have a large surface area and may also have high surface activity when some surface complexes are present. These surface complexes may be introduced on to or eliminated from the carbon surface by thermal and/or chemical treatment. Mercury, which is a danger to human health, may be found in some surface waters. In the past few years there has been a growing concern about the problem of mercury pollution and activated carbons could play an important role in the removal of Hg(I1) from waters.l This paper presents the results obtained by a study of the adsorption of mercuric chloride (HgC12) from aqueous solution on to activated carbons previously treated zyxw to introduce carbon-oxygen and carbon-sulphur surface complexes to determine their effect on the adsorptive capacity of the original carbons. 2. Experimental Three activated carbons obtained from commercial sources were used in the study: A (particle size 0.5-2.38 zyxwvut rnrn), B (1 .O-2.0 mm) and C (1 0-2.38 mm) which had all been treated with a solution (10 cm3 g-1 of carbon) of H202 (30%, w/v) at room temperature for 1 week. This treatment is expected2 to form different carbon-oxygen surface complexes and hereafter the resulting samples are referred to as AO, BO and CO. The carbons and the oxygenated samples were treated at 873 K under a flow of helium (50 cm3 min-1) for 6 h and then cooled to room temperature under helium; the resulting samples will be referred to as the original followed by 873. Present address: Universidad Nacional de Education a Distancia, Madrid, Spain. b Present address: Universidad de Alicante, Alicante, Spain. 0142-0356/82/0500-0575 $02.00 zyxwv 0 1982 Society of Chemical Industry 575