Sains Malaysiana 44(3)(2015): 429–439

Enhancement of Gaseous BTEX Adsorption on RH-MCM-41 by Chlorosilanes

(Peningkatan Penjerapan Gas BTEX pada RH-MCM-41 oleh Klorosilana)

T. AREEROB^1,4, S. CHIARAKORN²* & N. GRISDANURAK³

¹Division of Environmental Technology, Joint Graduate School of Energy and Environment

King Mongkut's University of Technology Thonburi, 10140 Thailand

²Division of Environmental Technology, School of Energy, Environment and Materials

King Mongkut's University of Technology Thonburi, 10140 Thailand

³Department of Chemical Engineering, Thammasat University, 12120 Thailand

⁴Center for Energy Technology and Environment, Ministry of Education, Thailand

Received: 14 January 2014/Accepted: 25 August 2014

ABSTRACT

In this research, the surface hydrophobicity of a mesoporous molecular sieve synthesized from rice husk silica, called RH-MCM41 was improved via silylation techniqueto enhance the adsorption efficiency of non-polar volatile organic compound. The effect of chlorosilane leaving on was analyzed with three silanes containing different numbers of chloride leaving group; trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMDCS) and methyltrichlorosilane (MTCS). The unmodified RH-MCM-41 was soaked in 100 mL of 5% v/v of silane reagent at 30ºC for 24 h. The results showed that the silane loading on the RH-MCM-41 was in the order of increasing number of leaving groups as MTCS > DMDCS > TMCS. The crystallinity results studied by X-ray diffractometry indicated that the silylation did not affect the hexagonal pattern of RH-MCM-41. However, the porosity of the silylated RH-MCM-41 was significantly decreased after silylation, especially by MTCS, due to pore blocking. After silylation, the adsorption performance of gaseous BTEX (benzene, toluene, ethylbenzene and xylene) on the silylated RH-MCM-41 was determined by gas chromatography equipped with flame ionization detector (GC-FID). From the results of humidity effect on adsorbability, the BTEX adsorption capacity of the unsilylated RH-MCM-41 was dropped a half, conversely the BTEX adsorption capacity of all silylated RH-MCM-41 was decreased in range of 20-30% when the relative humidity increased from 25 to 99%. This was indicated that the influence of humidity on the BTEX adsorption was relieved after silylation. In additions, the maximum BTEX adsorption capacity belonged to RH-MCM-41 silylated by TMCS which was recommended for the enhancement of non-polar volatile organic compounds adsorption.

Keywords: Adsorption; BTEX; MCM-41; rice husk silica; silylation

ABSTRAK

Dalam kajian ini, permukaan kehidrofobian penapis molekul mesoporous disintesis daripada sekam padi silika, dikenali sebagai RH-MCM41 bertambah baik melalui teknik sililasi untuk mempertingkatkan kecekapan penjerapan sebatian organik yang tidak berkutub. Kesan klorosilana yang tertinggal dianalisis dengan tiga silana yang mengandungi jumlah klorida berbeza meninggalkan kumpulan; trimetilklorosilana (TMCS), dimetildiklorisilana (DMDCS) dan metiltriklrosilana (MTCS). RH-MCM-41 yang tidak diubah suai, direndam dalam 100 mL 5% v/v bagi bahana uji silana pada 30ºC untuk 24 h. Hasil kajian menunjukkan bahawa bebanan silana ke atas RH-MCM-41 adalah dalam aturan penambahan bilangan meninggalkan kumpulan sebagai MTCS > DMDCS > TMCS. Keputusan habluran yang dikaji oleh belauan sinar-x menunjukkan bahawa sililasi tidak menjejaskan corak hexagon RH-MCM-41. Walau bagaimanapun, keliangan sililasi RH-MCM-41 menurun dengan sekata selepas sililasi, terutamanya MTCS, kerana menghalang liang. Selepas sililasi, prestasi penjerapan gas BTEX (benzena, toluena, etilbenzena dan xilena) pada sililasi RH-MCM-41 ditentukan melalui kromatografi gas dilengkapi dengan pengesan pengionan api (GC-FID). Hasil daripada serapan kelembapan menunjukkan kapasiti penjerapan BTEX sililasi RH-MCM-41 jatuh separuh, sebaliknya kapasiti penjerapan BTEX untuk semua sililasi RH-MCM-41 adalah menurun dalam julat 20-30% apabila kelembapan bandingan meningkat daripada 25 kepada 99%. Ini menunjukkan bahawa pengaruh kelembapan pada penjerapan BTEX lebih baik selepas sililasi. Sebagai tambahan, kapasiti maksimum penjerapan BTEX adalah kepunyaan RH-MCM-41 sililasi oleh TMCS yang dicadangkan untuk meningkatkan penjerapan-tidak berkutup organik meruap.

Kata kunci: BTEX; MCM-41; penjerapan; sekam padi silika; sililasi

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*Corresponding author; email: Siriluk.chi@kmutt.ac.th