MODIFIKASI PERMUKAAN SILIKA DENGAN ASAM FOSFONOASETAT DAN AMINOETILDIHIDROGENFOSFAT UNTUK ADSORPSI Co(II), Ni(II), Cu(II) DAN Zn(II); MODIFICATION OF SILICA SURFACE WITH PHOSPHONOACETIC ACID AND AMINOETHYLDIHYDROGENPHOPHATE FOR ADSORPTION OF Co(II), Ni(II), Cu(II) AND Zn(II)

Widjonarko, Dian Maruto, Nuryono

2015 | Tesis | FMIPA

Modification of silica gel surface with phosphonoacetic acid (PA) and aminoethyldihydrogenphosphate (AEPH2) through bridging group of ?–glycydoxyprophyltrimethoxysilane (GPTMS) and 1,4-dibromobutane and its adsorption characteristic toward Cu(II), Ni(II), Cu(II), and Zn(II) have been performed. The effect of NaOH and HNO3 in activation; effect of ethanol, toluene, and water in grafting of GPTMS on silica; and effect of water, tetrahydrofuran (THF), and dioxane in grafting of 2-aminoethyldihydrogenphosphate (AEPH2) on GPTMS grafted onto silica have been studied. The effect of GPTMS and 1,4-dibromobutane; PA and AEPH2; and rate, capacity, and selectivity of adsorption of resulted materials were evaluated also. The modification of silica was carried out in multisteps. Firstly, silica was activated with NaOH and HNO3 in various contact time. Then, GPTMS and 1,4- dibromobutane were grafted, followed with grafting of PA and AEPH2 on material previously resulted. The resulted materials were characterized its active sites and porousity with infra-red spectroscopy and adsorption-desorption of N2, respectively. While, the adsorption characteristic was studied by applying the materials produced in batch technique toward Co(II), Ni(II), Cu(II), and Zn(II) in aqueous solution. The unadsorbed metal ions were analyzed with flame–atomic absorption spectroscopy. In order to analysis the rate, capacity, and selectivity of adsorption, some isotherm and kinetics models were evaluated. The result of the study show that modification of silica surface has been succesfully performed. The resulted materials consist of silica centered with phosphonate and bridging with organosilane group. The resulted materials are mesoporous. The activator prefer NaOH to HNO3 in silica activation. The solvent prefer toluene to water and ethanol in grafting of GPTMS on silica. The solvent prefer water to THF and dioxane in grafting of AEPH2 on GPTMS grafted onto silica. The grafting of GPTMS and 1,4-dibromobutane result organosilane group while GPTMS result added active site of COC which able to form complex and chelate bonding with cations. The grafting of PA and AEPH2 result active site of POH and PO which able to exchange cations and able to form complex and chelate bonding, respectively. The grafting of PA result added active site of COO which able to form complex and chelate bonding while AEPH result NH which able to form complex and chelate bonding. This active sites and metal ion depend on pH. Cu(II) adsorption by resulted materials follow second order, whilst for Co(II), Ni(II), and Zn(II) follow to pseudo–2 order. Adsorption of Cu(II) on modified silica follow isotherm adsorption Freundlich model, whilst adsorption of Co(II), Ni(II) and Zn(II) follow isotherm adsorption Langmuir model. The capacity of resulted materials of PA are bigger than of AEPH2 while capacity of resulted materials of GPTMS are bigger than of 1,4-dibromobutane. Ionic potential effect is more dominant than active sites and porousity effect. The selectivity of resulted materials follow the order of Cu(II)>Co(II)>Ni(II)>Zn(II).

Kata Kunci : silica gel; modification; phosphonate; organosilane, selective adorbent