Precipitated Silica Derived from Palm Oil Mill Fly Ash: Kinetics and Characterization

Abstract

The silica extraction from palm oil mill fly ash (POMFA) using sodium hydroxide as one of viable processes for obtaining silica from agricultural waste was investigated. The effects of extraction time and temperature were closely examined to study the kinetics of the process. The fixed variables used in the present work were mass of POMFA 468.2 gram; the POMFA mass to NaOH volume ratio 0.2341 g/cm3; the concentration of NaOH 1.4 N and the stirring speed of 1065 RPM. The levels of temperature employed were 348 K, 358 K, 368 K and 378 K for different time durations up to 60 min. The mechanical fragmentation process was applied to obtain precipitated silica from the extracted silica. The precipitation conditions were: stirring speed of 1160 RPM, pH of 8.75, temperature of 303 K and precipitation time of 100 min. The shrinking core model (SCM) with intra-particle diffusion controlled mechanism and the Jander equation can satisfactorily represent the extraction process. The activation energy for silica extraction was 58.20 kJ/mol for the SCM with intra-particle diffusion and 62.22 kJ/mol for the Jander equation respectively. The precipitated silica agglomerate obtained at the time of 100 min has the median-weighed volume particle size distribution of 114.07 μm. The chemical composition and physical characteristic of precipitated silica which were analyzed with LPSA, XRF, XRD, FTIR and SEM are similar to the precipitated silica from the references.

Effective utilizations of palm oil mill fly ash for synthetic amorphous silica and carbon zeolite composite synthesis

“…If it is assumed that the carbon is fixed it can be calculated that of 60.11% silica can be extracted from the POMFA. This is in accordance with Utama et al, (2016) that reported at the similar conditions around 60% of silica can be extracted from POMFA [4].…”

“…The alkaline extraction combine with the sol-gel precipitation and mechanical fragmentation was applied to produce precipitated silica, the result was 60% of silica from the ash can be extracted. The silica content in the POMFA was 39% so from 1 ton of POMFA only 234 kg silica can be extracted [4]. The process above still produces waste of 766 kg.…”

“…The main composition of POMFA is carbon of 30% and silica of 39% [4]. The extraction process will decreased the content of silica, make the POMFA richer in carbon and still has significant silica content.…”

Green Route Synthesis of Amorphous Silica from Oil Palm Decanter Cake: From Literature Review to Experiments

“…The porous structure observed was mainly due to the high combustion temperature that created holes on the particle's surface, thus, creating a larger surface area on the particles (Yahya et al, 2010). As the temperature reaches up to 700C, more agglomeration into irregular shapes can be seen through images due to mineral content in the crystalline form as the particles become more brittle (Utama et al, 2018;Yang et al, 2022). These results can also be proven through EDX spectra in which the silica intensity increased with the temperature increase.…”

“…It can be observed that the particle size is smaller than 500 nm. The spherical clusters displayed in Figure 3f indicate the presence of amorphous silica aggregated due to the increase of pH during the treatment using an alkaline solution (Permatasari et al, 2016;Quercia et al, 2013;Utama et al, 2018). The EDX spectra showed an increase in the intensity of silica.…”