Waste to Valuable by-Product: Kinetic and Thermodynamic Studies of Cd, Cu and Pb Ion Removal by Decanter Cake

Palm oil mills generate about 4 - 5 tons of decanter cake for every 100 tons of palm fresh fruit bunch processed. Due to the high organic content, the decanter cake could be converted to adsorbent for the removal of metal ions from waste water. The decanter cake was first dried at 105 oC and then carbonized at 500 oC. Earlier data showed that 500 oC had highest performance in ions removal. The resulting carbonized decanter cake were tested for removing cadmium (II), copper (II), and lead (II) ions. Proximate analysis using thermogravimetry of decanter cake carbonized at 500 oC indicated that the adsorbent contained 4% moisture, 21% volatile, 23% fixed carbon, and 52% ash. Adsorption test was carried out by mixing 1.0 g of the decanter cake in 100 mL aqueous solution of the various ions. Langmuir and Freundlich isotherm models were used to fit the isotherm experimental data. The maximum uptakes of Cd, Cu and Pb onto the carbonized decanter cake in this study were estimated to be 24, 23, and 97 mg/g respectively. The adsorption kinetics was found to follow the pseudosecond-order kinetic model. Thermodynamic parameters such as standard enthalpy (H), standard entropy (S) and standard free energy (G) were determined

Technology Selection of Microalgae Thermochemical Conversion to Bio-Crude Oil

Microalgae as a third-generation biofuel source with various advantages is a potential part of renewable energy resources. Various studies on the conversion process of microalgae into biofuels have been carried out, one of which is the thermochemical process. The thermochemical conversion process is considered better than the biochemical process which has a low conversion rate and higher production costs. Recent researches state that to obtain bio-crude oil from microalgae through a thermochemical process, there are two alternative technologies that can be used, which are pyrolysis and liquefaction. In this research, a selection was made to determine which technology was better using decision making tools of Analytic Hierarchy Process (AHP) method. The evaluation criteria that have been used are technological (readiness level, energy efficiency, pre-treatment process, and product output), operational complexity, environment, and economy (investment cost and operation cost). The alternative technologies evaluated were pyrolysis with bubbling fluidized bed reactor, pyrolysis with circulating fluidized bed reactor, and hydrothermal liquefaction. From the results of pairwise comparisons, the technological criteria had the highest weight (0.343) and hydrothermal liquefaction technology was the best alternative technology among other alternatives (0.420). © Published under licence by IOP Publishing Ltd