Zaemah Jubri

Extraction of silica and alumina from coal fly ash for the synthesis of zeolites

This paper reports the extraction of soluble silicates and aluminates from coal fly ash using microwave irradiation from a domestic microwave oven. Fifteen experimental conditions for the extraction were obtained using Box-Behnken design through manipulation of three variables namely sodium hydroxide (NaOH) concentration, power level of microwave irradiation and exposure time; each variable has three values. The variables with their values were; NaOH concentration (2, 4 and 6 M), exposure time to microwave irradiation (1, 3.5 and 6 min) and power level of the irradiation (10, 50 and 100 Watts). Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) was used to study the amount of silicon and aluminium in the extracts. The extracted silicates and aluminates (after the molar ratio of SiO2 to Al2O3 was adjusted to unity by adding aluminium foil) were further incubated at 95°C for 72 hours. The products isolated from the 14 experiments were characterized by their XRD images and found to be Na-A zeolites, gibbsite and sodalite octahydrate.

Synthesis, Characterization and Sustained Release Properties of Zinc-Aluminium-9-Hydroxy-9-Flourenecarboxylate Nanocomposite

Zn-Al-9-hydroxy-9-flourenecarboxylate-layered double hydroxide, ZAF nanocomposite was successfully synthesized by direct self-assembly method with Zn to Al molar ratio, R = 4 and 0.4 M 9-hydroxy-9-flourenecarboxylate, 9H9F. Due to the inclusion of a new anion, 9H9F basal spacing expanded from 8.9 Å in the Zn-Al-layered double hydroxide, ZAL to 13.2 Å in the ZAF. The FTIR spectra of the hybrid nanocomposite show resemblance peaks of the ZAL and 9H9F indicating the inclusion of the organic compound into the LDH interlamellae. The percentage loading of 9H9F was found to be 75.9 % (w/w). Sustained release of 9H9F from ZAF into various aqueous solutions was found to be dependent on the incoming anion, with the percentage saturated release of 94%, 72%, and 15% in sodium phosphate, sodium sulfate and sodium chloride aqueous solution 0.0005 M, respectively. This study indicates that ZAL can be used as a host carrier for plant growth regulator, 9H9F with sustained release capability.

Controlled release of herbicide into water from beta-naphtoxyacetic acid-layered double hydroxide nanohybrid formulation

At present, the use of huge quantities of herbicides in conventional agriculture has lead to some major environmental problems. Controlled release formulations (CRF) are now being developed to avoid such problems. The release of beta-naphtoxyacetic acid (BNOA) into aqueous solution from controlled-release formulation (CRF) prepared by the intercalation of BNOA anion into Zn-Al-layered double hydroxide (ZAL) was studied. CRF consisting of organic-inorganic nanohybrid material was synthesized by coprecipitation method using BNOA as guest anion and Zn-Al-LDH as the inorganic host. As a results of successful intercalation of BNOA ion into Zn-Al-LDH, the powder X-ray diffractogram shows that the basal spacing of Zn-Al-LDH with BNOA as interlayer ion expanded from 8.93 A to 19.46 A. This expansion is to accommodate BNOA ion for the formation of Zn-Al-BNOA nanocomposite (ZAB). The reverse process, i.e., the deintercalation or release of the guest, BNOA was found to be rapid initially, followed by more sustained release thereafter and this behavior was dependent on the type of anions and the concentrations of the release medium, the aqueous solution. The mechanism of release has been interpreted on the basis ion-exchange process between the BNOA anion intercalated into the interlamellae host and carbonate or chloride and/or hydroxyl anions in the aqueous solution.

Synthesis and physicochemical characterization of Mg-Al-flufenamate-layered double hydroxide

A nonsteroidal drug, flufenamic acid (FA) was successfully intercalated into magnesium-aluminium-layered double hydroxide, MAL for the formation of magnesium-aluminium-flufenamate-layered double hydroxide, MAF by self-assembly technique. As a result of the successful intercalation, basal spacing increased from 9.8 Å in the MAL to 23.5 Å in the MAF hybrid nanocomposite. The FTIR spectra of the MAF hybrid nanocomposite show resemblance peaks of the MAL and FA suggesting the inclusion of the organic compound into the MAL interlamellae. The percentage loading of FA was found to be 74.4 % (w/w) calculated from the percentage of carbon in the resulting material, MAF.

Behavior of Layered Double Hydroxides Having Different Divalent Transition Metal Groups

The layered double hydroxides (LDHs) with different divalent transition metal groups and nitrate as a counter anion were investigated. Three d-block divalent metals namely cobalt (Co), nickel (Ni) and copper (Cu) were selected. The cobalt/aluminium (CoAN)-, nickel/aluminium (NiAN)- and copper/aluminium (CuAN)-layered double hydroxides were successfully synthesized via co-precipitation method. All the obtained LDHs were characterized by PXRD, FT-IR, ICP-OES, CHNS and TGA/DTG analysis. Interestingly, behavior of the LDHs was dependent on the size of divalent cations. PXRD showed the basal spacing decrease in the order NiAN (0.88nm)> CuAN (0.87nm) > CoAN (0.74nm), and in a linear correlation with the increasing radii of the divalent cations. Similar trend is observed for the weight loss of LDHs, where NiAN has the highest weight loss (53%), followed by CuAN (43%) and CoAN (34%). Further elemental analysis showed the content of trivalent metal cations, nitrate anions and water molecules in the LDHs decrease with the increasing radii.