Mechanisms of Competitive Adsorption Organic Pollutants on Hexylene-Bridged Polysilsesquioxane.

De-Rong Lin,Douglas Loy,Bao-Shan Xing,Hong You,Li-Jiang Hu

doi:10.3390/ma8095275

Abstract

Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS) are a promising new class of adsorbent for the removal of organic contaminants from aqueous solutions. These hybrid organic-inorganic materials have a larger BET surface area of 897 m2·g−1 accessible through a cubic, isotropic network of 3.82-nm diameter pores. The hexylene bridging group provides enhanced adsorption of organic molecules while the bridged polysilsesquioxane structure permits sufficient silanols that are hydrophilic to be retained. In this study, adsorption of phenanthrene (PHEN), 2,4-Dichlorophenol (DCP), and nitrobenzene (NBZ) with HBPMS materials was studied to ascertain the relative contributions to adsorption performance from (1) direct competition for sites and (2) pore blockage. A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment.

Highlights

Mesoporous organosilicas, such as Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS), have good potential for effectively removing a wide range of organic pollutants from water.Organic pollutants include organic compounds varying in molecular weight between a few hundredDaltons and one hundred thousand Daltons [1] with a wide range of functionality and shapes
The adsorption capacity of the HBPMS materials are relative to the pore size, competitive adsorption sites, and pore blocking
The FM model is applicable for HBPMS’ competitive adsorption of organic pollutants

Summary

Introduction

Mesoporous organosilicas, such as Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS), have good potential for effectively removing a wide range of organic pollutants from water.Organic pollutants include organic compounds varying in molecular weight between a few hundredDaltons (peptides) and one hundred thousand Daltons (proteins) [1] with a wide range of functionality and shapes. Mesoporous organosilicas, such as Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS), have good potential for effectively removing a wide range of organic pollutants from water. Organic pollutants include organic compounds varying in molecular weight between a few hundred. Daltons (peptides) and one hundred thousand Daltons (proteins) [1] with a wide range of functionality and shapes. The efficacy of adsorption decreases substantially with increasing concentration for all sorbents. There are two mechanisms for inhibition of pollutant adsorption: direct site-competing (SC) and pore blockage (PB). Direct competition for available adsorption sites, and the resulting reduction of adsorption capacity, is mainly caused by organic pollutants with lower molecular weights [2]. Pore blockage is mainly caused by larger molecules, which adsorb in larger pores and constrict, possibly completely blocking the entrance to smaller pores

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