Journal of Hazardous Materials 164 (2009) 1439–1446 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Comparative study of the removal of phenolic compounds by biological and non-biological adsorbents Abel E. Navarro a,∗ , Norma A. Cuizano b , Jose C. Lazo c , María R. Sun-Kou c , Bertha P. Llanos b a Department of Chemistry, Graduate School of Arts and Sciences, New York University, New York, NY 10003, United States b Departamento Académico de Química, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima L31, Peru c Sección Química, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Lima L32, Peru article info Article history: Received 10 February 2008 Received in revised form 10 September 2008 Accepted 17 September 2008 Available online 27 September 2008 Keywords: Exchanged bentonite Cross-linked algae Partition coefficient pH Adsorption abstract The ability of biological and non-biological adsorbents to remove 2-nitrophenol (2-NP) and 2- chlorophenol (2-CP) from aqueous solutions in batch experiments at room temperature was compared. The marine seaweeds Macrocystis integrifolia Bory (S1) and Lessonia nigrescens Bory (S2) were cross- linked with CaCl 2 to enhance their mechanical properties. Natural bentonite was chemically exchanged with hexadecyltrimethylammonium bromide (B1) and bencyltriethylammonium chloride (B2) to increase their affinity towards organic compounds as well. The adsorption capacity of all of the adsorbents strongly depends on solution pH, whereas equilibrium assays showed a mixed mechanism according to the Langmuir and Freundlich isotherms. The maximum adsorption capacity of 2-NP follows the trend: S1 > S2 > B2 > B1 within the range of 97.37 and 18.64 mg g -1 whereas for 2-CP, it ranged between 24.18 and 9.95 mg g -1 with the trend: S1 > S2 > B2 ≈ B1. The importance of the octanol–water partition coefficient as the main factor on the adsorption of these compounds on two different kinds of adsorbents is discussed. © 2008 Elsevier B.V. All rights reserved. 1. Introduction At present, one of the most serious concerns faced in the natural environment is chemical contamination with organic and inor- ganic substances catalyzed by the presence of heavy metals and phenolic compounds [1,2]. The presence of such compounds in an aquatic medium originates changes in chemical (pH, chemical oxy- gen demand, alkalinity, acidity, dissolved oxygen, etc.), physical (color, temperature, odor, viscosity, turbidity, etc.) and biological properties, damaging the water quality for human usage and upset- ting the environmental equilibrium [2,3]. The uptake of toxic and heavy metals ions from waste waters and industrial wastes by cer- tain types of microbial biomass especially algae [4,5], fungi [6,7] and other biological adsorbents [8,9] has been the subject of many recent studies. Natural clays have also shown an increasing number of applications on the removal of heavy metals [10–12]. Among the different pollutants of aquatic systems, phenols are considered as priority contaminants since they are harmful to plants, animals and humans, even at low concentrations [3,13]. Due to their extensive use and slow degradation, nitrated and chlori- nated phenols readily enter the environment by agricultural runoff ∗ Corresponding author. Tel.: +1 646 2862082; fax: +1 212 9954475. E-mail address: aen234@nyu.edu (A.E. Navarro). of pesticides, effluents from oil refineries and plastic industries and by leachates emerging from waste deposits produced by microbial hydrolysis and photodegradation of several organophosphorous pesticides, such as parathion [14,15]. Activated carbon is one of the most efficient adsorbents for these organic molecules, as it possesses a high surface area per unit mass and exhibits a high affinity for phenolic compounds [16]. Unfortunately, due to the high cost of activated carbon, it is not an economical adsorbent compared with low cost, naturally occurring alternatives. These non-expensive adsorbents remove trace amounts of organic contaminants from wastewaters where other sophisticated techniques such as ionic exchange, osmosis, and solvent extraction are not applicable. Consequently, the envi- ronmental biotechnology is in a constant search of alternative, less expensive and viable techniques for the removal of these phenolic compounds at very low concentrations. Adsorption using naturally occurring adsorbents has become a cheap and efficient tool, easily applicable in the detoxification of residual waters from industries and mines showing positive results. High efficiency on the elimina- tion of artificial colorants and phenols from aqueous solutions by marine seaweeds and natural clays has been observed in previous studies [17–22]. Peru is widely known for its diversity of natural resources. Marine seaweeds are in such abundance on the shores of beaches as to cause unsightly accumulation. Also, natural clays of the type 0304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2008.09.077