Abstract Zinc ferrite (ZnFe2O4) nanoparticles have attracted the attention of researchers because of their unique chemical properties and particle-size-dependent magnetic properties. High-surface-area spinel ferrites have numerous technical applications in areas such as high-density information storage, ferrofluids, and catalysis. The coprecipitation technique is the preferred method for preparing nanoscale ZnFe2O4 because it results in a small crystals with a uniform size distribution. In this study, the synthesis was conducted in solution for 48 h, followed by sintering at 1000°C for 1.5–3.5 h. The smallest crystals (70.58 nm) were found in the sample sintered for 2.5 h. Fourier transform infrared spectroscopy (FTIR) functional-group analysis confirmed the presence of Fe–O and Zn–O bonds of cations in octahedral and tetrahedral sites. The ZnFe2O4 sintered for 3.5 h was superparamagnetic. The characterization results suggest that the obtained ZnFe2O4 could be used as a nanofluid in heat exchangers.

Abstract: Among the renewable biomass fuel alternatives, microalgae are the most important fiiture choices owing to its f'ast growth rate and great capability for C02 fixation. There are vaxious species in the world, in which each species has its characteristics. This work presents a prospect of marine microalgae Isochrysis galbana for renewable fuel feedstock regarding its biomass abundance, physicochemical properties, and thermal characteristic. The seawater médium in the Erlenmeyer flask was used for the algal culturing. The biomass abundance, in term of specific growth rate and doubling time, was assessed by calculating the culture médium cells number with a hemocytometer and optical microscope. Harvesting was done by precipitating biomass with caustic soda, subsequently filtering, and washing it with distilled water. The biomass sediment had been sun-dried for three days, and then dried biomass was crushed by using the mortar to be a powder. The proximate analysis was arranged by conducting an experiment in according to the test method of ASTM D 3173-11, ASTM D 3175-11, ASTM D 3172-13 and ASTM D 3174-12 for specifying the content of moisture, volatile matter, fixed carbón, and ash of the sample, respectively. The heating valué was estimated by using adiabatic bomb calorimeter. The chemical composition of biomass was determined by Energy-dispersive X-ray (EDX) spectrometry. The biomass cellular macromolecular compounds were also evaluated by Fourier transform infrared (FTIR) spectroscopy and compared with its residue. Through eight days observation, it was noticeable that Isochrysis galbana has a specific growth rate of 0.18 d-1 and a doubling time of 3.85 d. The respective moisture, volatile matter, fixed carbón, and ash content were 12.98, 40.10, 7.47, and 39.45 (%, air-dried basis). The energy content algal biomass was 16.22 MJ kg-1. This current investigation encourages that Isochrysis galbana can be viable as one of a future sustainable solid biofuel feedstock.