Adsorption Capacity and Mechanism of Expanded Graphite for Polyethylene Glycol and Oils

Abstract

Expanded graphite (EG) shows higher adsorption capacity for oils such as salad oil and SD300 oil than polyethylene glycol (PEG) with different MW (4000, 10000, 20000). To illustrate their different adsorption mechanism, adsorption capacities of EG for these pollutants are firstly detected. And then stepwise adsorption for oils is carried out with EG which has been saturated first by PEG with different MW. Then difference between stepwise adsorbance of oil is checked with deviation analysis. Scanning electronic microscopy (SEM) analysis is used to show structure difference of EG adsorbed different adsorbates. It is testified adsorption isotherms of PEG are all type I, PEG molecules lay flat on EG surface and equilibrium adsorbance decrease with the increase of PEG MW. Adsorbance for SD 300 oil and salad oil can reach 131.3 g/g and 127.8 g/g respectively. Deviation analysis for stepwise adsorbance of oil shows no statistical significance. EG saturated firstly by PEG, still has an average adsorption capacity of 98 g/g for SD300 oil and 85 g/g for salad oil and it does not change with the initial PEG concentration. SEM photos illustrate the adsorption of oil on EG is mainly filling. In the adsorption of PEG water solution, there is severe breakage of the V-type pore and shrinkage of the particle.

Adsorption Characteristics of Polyvinyl Alcohols in Solution on Expanded Graphite

“…Equilibrium adsorbances are less than 20 mg/g among the detected PVA solution and it decrease with the increase of PVA' DP. The results are just as the adsorption of linear PEG on EG 25 . The planar structure and large molecules of PVA might form certain kinds of conformation on the surface of EG, which might reduce the adsorbed sites and make the further adsorption difficult.…”

“…The pore in EG ranges from several nm to hundreds µm 15 , it has been used as absorbent for its high adsorption capacity for organic materials, such as heavy oil and biomedical molecules [16][17][18][19][20][21] . Pang et al have studied the adsorption capacities of EG for oil, dyes, aromatic sulfonates, polyethylene glycol (PEG) [22][23][24][25] , results indicated EG show definite adsorption capability for these organic substances, especially for oils. Both adsorbates molecular weight and molecular structure affected adsorption type, saturation adsorbance.…”

Thermodynamic analysis of fatty acid harvesting by novel carbon-based adsorbent

“…Haghi et al (2015) has reported that the specific surface area of a carbon is not necessarily proportional to the adsorption capacity of the activated carbon because the large surface area of activated carbon is mainly due to the contribution of micropores, which can be hardly available for high molecular weight and slowly diffusive adsorbates such as FA. In the adsorption of FA with activated carbon as adsorbent, the adsorbed molecules lay flat on activated carbon surface (Pang 2010). In contrast to the adsorption on activated carbon, most of the pores are exposed to the surface contacting with aqueous solution (Fig.…”

Thermodynamic and Kinetic Study of Competitive Adsorption Between Sodium Anthraquinone-1-Sulfonate and Xylenol Orange on Expanded Graphite

“…It has attracted attentions of scientists and engineers as for its high adsorption capacity to organic materials, such as heavy oil, dyes, aromatic sulfonates, poly(ethylene glycol), etc. [11][12][13][14][15][16][17][18] . Actually, pollutants rarely exist solely in single component, but the adsorption research for them on expanded graphite often carried in single component system.…”