Characterization of modified polypropylene powder (Accurel) and its use for adsorption of phenolics from aqueous solution

Abstract

The polypropylene based Accurel has been modified using surfactant and then characterized for selective adsorption of phenolics. The pore distribution falls between macroporous and mesoporous domains. The SEM images of Accurel reveal that it has porous structure of typically 73% void volume with cells of 5-10 μm connected by pores of 0.0028 μm diameter. The BET surface area of the Accurel is typically found as 27 m²/g. The titled adsorbate-sorbent system follows L2 type of adsorption. The adsorption of studied phenolic acids depends on several factors, such as pK_a, ionic strength, and steric effect (molecular size). The adsorption coefficients for the studied phenolics follow the sequence: chlorogenic acid > p-cumaric acid > syringic acid > p-hydroxy benzoic acid. The adsorption capacity of phenolics grows with increase in –OH groups in the structure of the acids. The amount of adsorbed phenolics increases with increasing ionic strength and obeys the sequence: Cl_{<img src='http://www.niscair.res.in/jinfo/subscript28.gif' border=0>} < <i>S</i>O_{_{<img src='http://www.niscair.res.in/jinfo/subscript27.gif' border=0>}} < PO_{_{<img src='http://www.niscair.res.in/jinfo/subscript26.gif' border=0>}}. Similarly, the cations are added in the same concentration range as anions and the effectiveness is found to obey the sequences: Na⁺< Ca²⁺< fe³⁺. The adsorbed amount decreases at both high and low <i style="mso-bidi-font-style:normal">p</i>H values. Adsorption is found to increase significantly with increase in ionic strength, suggesting a role for the hydrophobic force in this adsorption process. Urea, a hydrogen bond breaker, reduces the adsorption, suggesting that the hydrogen bonding may also play a role in the adsorption of phenolics on modified Accurel. The modified Accurel shows significant sorption capacity for phenolics under suitable experimental condition and hence, will serve as a useful sorbent which can be extended to other chemical systems for the isolation of anti-oxidant phenolics. Furthermore, Accurel is available commercially and hence, scalable for industrial purpose.

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