No abstract

Cogon grass (Imperata cylindrica), an invasive, unwanted grass was used and evaluated for its applicability for the sorption of engine oil. Other than dried and ground for smaller size, no notable treatment was performed on the cogon grass. The physical and chemical properties of cogon grass were characterized by ash content, bulk density, pH slurry, and Field Emission Scanning Electron Microscopy (FESEM). The oil sorption was performed in a batch adsorption system. The effects of contact time, dosage of adsorbent and oil retention were investigated. The bulk density and ash content of the prepared carbon was 0.34 g/ml and 7.80 %, respectively. The pH slurry value was near neutrality (6.48). FESEM micrograph of cogon grass showed jagged and rough surface. FTIR spectra revealed the presence of aromatic rings of lignin and some aromatic compounds associated with CH. Carbon, hydrogen and nitrogen (CHN) analysis revealed that 41% of cogon grass consists of carbon. The cogon grass was observed to wet oil almost instantly with sorption equilibrium time of 5 min. The dose of cogon grass was found to slightly affect the sorption capacity. Oil retention experiments reveal the good ability of cogon grass to hold oil with about 96% retention after 24 h dripping. This study may provide an insight on the usefulness of cogon grass for removal of engine oils.

The uptake of Acid Blue 29 (AB29), Reactive Orange 16 (RO16) and Reactive Red 120 (RR120) from aqueous solutions by calcined (CLDH) and uncalcined Mg/Al layered double hydroxide (LDH) has been investigated. The adsorption process was conducted in a batch mode at 25 °C. Anionic dye removal was more efficient using the CLDH rather than LDH. The adsorption process by CLDH involved reconstruction and hydration of the calcined LDH and intercalation of AB29, RO16 and RR120. Physical characterization using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) were used to ascertain the 'memory effect' phenomenon that is structural reconstruction to regain its original LDH after rehydration. To gain insight into the mechanism of adsorption by CLDH, the pseudo-first order (PFO) and pseudo-second order (PSO) and intraparticle diffusion (IPD) kinetic models were used to analyse experimental data. Based on the correlation coefficient (R 2 ), the PSO has better fitting (R 2 = 0.987 -1.00) compared to PFO (R 2 = 0.867 -0.990). Furthermore the values of maximum adsorption capacity, (q e ) calculated from PSO model are consistent with the experimental q e indicating that the experimental kinetic data for AB29, RO16 and RR120 adsorption by CLDH are suitable for this model. Recycling of the adsorbent, in cycles of calcination-reconstruction process promised a possibility of regeneration of CLDH.Keywords: calcined, adsorption capacity, reconstruction, memory effect, regeneration Abstrak Penyingkiran pewarna Acid Blue 29 (AB29), Reactive Orange 16 (RO16) dan Reactive Red 120 (RR120) daripada larutan akues menggunakan Mg/Al dwi-hidroksida berlapis berkalsin (CLDH) dan tanpa kalsin (LDH) telah dilakukan menggunakan kaedah berkelompok pada suhu 25 °C. Penjerapan bahan pewarna menggunakan CLDH didapati lebih berkesan berbanding LDH. Penjerapan bahan pewarna oleh CLDH berlaku melibatkan proses penghidratan dan penstrukturan semula CLDH dan juga apitan AB29, RO16 dan RR120. Pencirian fizikal pada bahan penjerap yang diperolehi dengan menggunakan kaedah Pembelauan Sinar-X (XRD), Mikroskopi Imbasan Elektron (SEM) dan Spektroskopi Inframerah Transformasi Fourier (FTIR) telah digunakan untuk mengenalpasti fenomena 'kesan memori', iaitu proses penstrukturan semula kepada LDH selepas berlaku penghidratan. Cerapan lebih lanjut mengenai mekanisme proses penjerapan ini, model-model kinetik pseudo tertib pertama (PFO), pseudo tertib kedua (PSO) dan resapan intrapartikel (IPD) telah digunakan untuk menganalisis data ujian. Berdasarkan nilai pekali korelasi (R 2 ), model PSO didapati lebih sesuai (R 2 = 0.99 -1.00) berbanding PFO (R 2 = 0.85 -0.99). Fakta ini diperkukuhkan lagi dengan nilai kapasiti penjerapan maksimum, (q e ) hasil pengiraan menggunakan PSO yang didapati konsisten dengan q e ujian (q e, expt .) untuk AB29, RO16 dan RR120. Kitaran semula bahan penjerap melalui beberapa siri kitaran pengkalsinan-penstrukturan semula juga didapati dapat menjanjikan penjanaan semula CLDH.

Air quality and pollution may be partly assessed by examination of rainwater compositions. Long term monitoring is essential in detecting signs of changing trend and hence any plausible air pollution and atmospheric acidification. Weekly samples of rainwater were collected by using a wet-only sampler at Global Atmospheric Watch (GAW) station in Danum Valley, Sabah in East Malaysia for a period between January 2005 and December 2006. Composition of wet deposition was determined for major cations (H + , Na + , K + , Ca 2+, Mg 2+, and NH 4 + ) and major anions (Cl − , NO 3 − SO 4 2− , CH 3 COO − and HCOO − ). In addition, the pH, electroconductivity and volume of rainwater were also determined. The results reveal that there was a steady decrease in pH of rainwater from annual average of 5.37 in 2005 to 5.14 in 2006. These pH values were below 5.6, the limiting value for clean rainwater. The lowest value recorded was 4.79 in October 2006 while the highest was 5.80 in January 2005. This is a worrying indication that atmospheric acidification may has made its presence felt in this remote area which was destined to be pristine environment. The volume-weighted mean concentrations of major ions followed the order: H + > SO 4 2¯ > Cl¯ > Na + > Ca 2+ > NO 3¯ > NH 4 + > K + > Mg 2+ > acetate > oxalate > formate. Both acidic and basic species concentrations were much lower compared to typical values in urban areas. The acid rain precursors; SO 4 2− and NO 3 − were well correlated and so were the sea-salt species, Mg 2+, Na + and Cl¯. The buffering systems to potential acidity are mainly due to crustal origins (Ca 2+ ) and anthropogenic activities (NH 4 + ) with contribution from sea salts (Na + , Mg 2+ and K + ). Biogenic emissions producing weak organic acids was negligible.

This study is on the distribution of rare earth elements (REEs) concentrations in sediments collected from 113 sampling locations of Linggi River. The analysis of sediment samples was performed by Neutron Activation Analysis (NAA) and Inductively Coupled Plasma – Mass spectrometer (ICP-MS). The main compositions of Linggi river sediments were silt > sand > clay. The mean of total concentrations of REEs (ΣREE), light REEs (ΣLREE) and heavy REEs (ΣHREE) in Linggi sediment were 249, 228, and 22.0 mg/kg, respectively. The results of Linggi river sediment were normalised to several reference shale values. REEs of Linggi river sediments were comparable to MUQ reference shale values. Enrichment factors (EF) of mean values indicate Linggi River sediment can be categorised as having minor to moderate enrichment.