Pillared graphene oxide composite as an adsorbent of soluble hydrocarbons in water: pH and organic matter effects

• Published in: Journal of environmental management 2020-04, Vol.259, p.110044-110044, Article 110044
• Main Authors: Flores-Chaparro, C.E., Castilho, C.J., Külaots, I., Hurt, Robert H., Rangel-Mendez, J.R.
• Format: Article
• Language: English
• Subjects: Adsorption; Chitosan; Graphene oxide; Graphite; Hydrogen-Ion Concentration; Oxides; Pillared composite; Soluble-hydrocarbons; Water
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.110044

Graphene oxide (GO) is a single-atom-thick sheet of carbon with oxygen-containing functional groups decorating its basal plane and edge sites. Most of its high surface area can be lost due to restacking of individual layers during the synthesis and drying of GO-based bulk sorbents. There is great interest to increase the specific surface area of graphene-based sorbents by introducing organic molecules as “pillaring agents” between GO sheets to hinder the stacking process and create sorbents with elevated surface area. This work synthesizes pillared GO by introducing chitosan (CS), a linear polysaccharide with various molecular weights. A composite of low molecular weight CS at a CS/GO ratio of 0.1 is shown to have the highest specific surface area (up to 70.5 m2/g) in comparison to the medium and high CS molecular weight, pristine GO, and the CS/GO composite materials. The affinity of the optimized GO/CS composites towards benzene, toluene, and naphthalene was evaluated at 19.3 mg/L of organic matter content while altering pH. Sips and Langmuir adsorption isotherm models well described the adsorption behavior, and benzene adsorption performance was reduced at low pH. Related to the presence of dissolved organic matter (DOM) in solution, lower diffusivity constants (k1) in hydrocarbon systems were recorded. Our results demonstrate the feasibility of CS as a potential pillaring agent in CS/GO composites to increase specific surface area and enhance the capture of soluble hydrocarbons from aqueous solutions. [Display omitted] •Low-molecular-weight chitosan optimized a pillared effect on graphene oxide.•An optimized chitosan/graphene oxide ratio of 0.1 achieved a surface area of 70 m2/g.•Medium and high molecular weight chitosan produced a little or no pillaring effect.•Composite had 2 to 4-fold the adsorption capacity of graphene oxide.•The removal decreased with increasing [H+] due to the amino groups protonation.