No abstract

The environmental footprint for microalgae based biofuel can be reduced by coupling the microalgae cultivation with wastewater treatment. In the present study, the nutrients source for microalga Chlorella vulgaris was replaced by municipal wastewater from wastewater treatment plant located at USM Engineering Campus, Penang. All cultivation experiments were conducted in 5 L photobioreactors (PBRs) under indoor condition with illumination from artificial lights and compressed-air aeration. The growth performances of microalga C. vulgaris and nutrients uptake from wastewater were monitored throughout a 13-day cultivation period. The nutrients removal efficiency (NRE) for total nitrogen (TN) and total phosphorus (TP) by microalgae are 72.1 wt% and 89.7 wt%, respectively under the optimum cultivation conditions. Subsequently, microalgae biomass was collected by flocculation method, followed by extraction of lipid and transesterified to biodiesel. It was found that the biomass collected under optimum cultivation conditions achieved a maximum biomass dry weight density (N) of 0.76 g/L (or an equivalent biomass daily productivity, P of 58.6 mg/(L･d)).

This study was carried out in order to investigate the formation of hydroxyapatite (HAp) coatings on etched Ti mesh substrate using electrodeposition technique. The coatings were deposited from solution containing CaCl 2 and NH 4 H 2 PO 4 (with Ca/P ratio being 1.67) by maintaining cathodic potentials for -0.8 V and -1.5 V vs Ag/AgCl for 30 min at 80 o C. On the other hand, chitosan solution was also added into bath solution to study its effect on coatings morphology. The surface morphology and the elemental compositions of the Ti surface before and after deposition were observed by FESEM and EDAX, respectively. Etching process has changed the morphology of the Ti surface from smooth to rough surface. HAp coatings deposited at -0.8 V and -1.5 V have similar morphology with flower-like structure. However, the coatings are more dense and compact when deposited at higher potential (i.e.: -1.5 V). When chitosan was added into bath solution, the morphological structure of the coating was significantly changed from flower-like structure to flake-like structure interconnected with net-like structure of chitosan.

In this study, hydroxyapatite (HAp) coatings were electrodeposited onto titanium (Ti) substrates using an aqueous solution containing 0.167 M CaCl 2 + 0.1 M NH 4 H 2 PO 4 . The effect of chitosan on the formation of HAp coatings were investigated by adding various amount of chitosan ranging from 5 to 20 vol. %. The electrodeposition was carried out at 80 o C for 30 min under constant applied potential at -1.5 V vs Ag/AgCl. Prior to electrodeposition, the Ti substrates were pre-treated by acid etching to remove oxide and obtain desired roughness surface. The incorporation and intermingling of chitosan in the HAp coatings reduce the amount of space found between the needlelike structures in the pure HAp coatings by 'filling in' the space. However, excessive amount of chitosan added in the deposition solution (i.e.: 20 vol. %) caused it to compete with calcium ions to incorporate with phosphate ions and dominating the coatings. XRD patterns, FTIR spectra and EDAX analyses confirmed that the presence of chitosan in the HAp coatings. So, considering its economic and simple production, a hybrid HAp/chitosan coating is thought to be an attractive candidate for future applications as biomedical implants material.