Efficiency of Fe3O4 Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

Abstract

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe3O4) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe3O4) NPs, (ultrasonic-Fe3O4, ozone-Fe3O4 and microwave-Fe3O4) in different treatment times. Moreover, the green synthesized Fe3O4 NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe3O4 respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe3O4 NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R2 = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis.

Enhancement of biogas production from individually or co-digested green algae Cheatomorpha linum using ultrasound and ozonation treated biochar

“…The VS content of C. linum is 72.37 % and a C/N ratio was 9.46 ( Table 3 ). The majority of literature [18] recommends a working C/N ratio of between 20 and 30 with an ideal ratio of 25 for anaerobic bacterial growth in the AD system, which is still significantly lower than the measured ratio for C. linum .…”

“…Because moderate biochar addition effectively mitigated VFA accumulation and resulted in increased methanogenic activity [24] , whereas a higher biochar concentration resulted in increased propionic acid accumulation and lowered the stability of the AD process [25] , the authors concluded that moderate biochar addition was the most effective option for their research. Moreover, according to a study by Lü et al [8] , methane output increased by 23.5–47.1 percent in digesters containing biochar compared to controls that did not include biochar [17] , [18] , [19] , [20] , [21] . Total methane outputs compared to the control group increased by 12.07 percent, 21.19, 33.65, and 45.66 percent in the biochar treatment groups.…”

“…It was necessary to treat and crush the dry algae to a particle size of around 0.5 mm before storing it until it was required for further usage. It has been computed that the amount of dry matter follows the literature [17] , [18] . The ash concentration of powdered dried samples was determined by ashing them for 24 h in a muffle furnace set to 550 °C.…”

“…BET analysis was performed using Mini II, BEL Japan equipment, Inc., Osaka, Japan. Thermal studies were done on both manufactured biochars using the SDT650-Simultaneous Thermal Analayzer equipment in the range of 50 to 900 °C using a 5 °C per minute ramping temperature [18] .…”

“…On the other hand, biochar made from coconut shells and corn straws showed a gradual rise in methane production after acclimation [16] . They reported that adding unmodified biochar at concentrations of 50 and 100 mg to algae significantly increased their biogas production compared to the same amount of algae that had not been treated [16] , [17] , [18] . Using 100 mg of unmodified biochar combined with 10 mg of Fe 2 O 3 in the inoculum, it was revealed that a maximal amount of biogas (219.5 mL/g VS) was formed, and the highest amount of biogas generation was achieved.…”