This work aimed to synthesize MnFe2O4 nanoparticles using the coprecipitation method. Manganese chloride dihydrate (MnCl2.4H2O) and iron sand from South Cianjur, Indonesia, were used as a precursor for MnFe2O4 nanoparticle synthesis. The iron sand elements and compounds were tested using X-Ray Fluorescence (XRF). MnFe2O4 nanoparticle was characterized using X-Ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX), and Vector Network Analyzer (VNA). The X-Ray Fluorescence test result showed that 70.54% of South Cianjur contained iron sand. The SEM test result showed that the nanoparticles have an average size of  73.75 nm with a round shape, which was attributed to the agglomeration process. The EDX test result showed that the synthesized nanoparticle contained only Mn, Fe, and O elements without contaminants. The XRD test result showed that the crystal phase of MnFe2O4 was formed with a crystal size of less than 27 nm. The largest reflection losses in the 11.5 - 12.5 GHz range were found in MnFe2O4 with 1:2 variation, i.e., 35.08 dB. This study found that adding iron sand increases MnFe2O4 microwave absorption.

Characterizations of membranes made from cellulose coconut fiber-fiber glass as H₂O separators in water of electrolyzer has been done. The separators membrane was successfully made with a manual and simple technique, mixing cellulose fiber material produced from the modification of coconut fibers with NaOH immersion process. Cellulose fiber mixed with fiber glass in the composition of 50:0, 40:10, 30:20, 20:30, 10:40, 0:50 (%wt) to get hybrid composite. The results of testing the ability of the membrane as a separator produce H₂ gas concentrations that are more increased than without using a separator. The optimum value produced is 300 ppm in sample 1 which is 50:0:50 %wt, while the H₂ gas production without using a separator which is 51 ppm. For physical properties testing, the addition of mass percent of celluose coconut fiber affects the physical and electrical properties of membrane where the optimum value of % porosity of the material obtained is 73 %, swealling value is 77,5 % and the conductivity value of the material amounting to 1,572 x 10 ^-7 S/cm.

Characterizations of membranes made from cellulose empty palm oil bunches-fiber glass as H2O separators in water of electrolyzer has been done. The separators membrane was successfully made with a manual and simple technique, mixing cellulose fiber material produced from the modification of oil palm empty bunches fibers (OPEBF) with a steam explosion in 12 % NaOH immersion. Cellulose fiber mixed with fiber glass in the composition of 30:20:50 (%wt)and dried with variations in heating temperature 60oC, 70oC, 80oC, 90oC and 100oC to get a composite. The results of Characterization the ability of the membrane as a separator produce H2 gas concentrations which is more increased than without using a separator. Where is the good and stable value for the membrane as a separator in heating temperature 70oC with a percentage of membrane porosity is 34.9%, the percent value of water absorption (swealling) is 46.93% and membrane conductivity is 1.33 x 10-10 S/cm and SEM results show sample in heating temperature 70oC has more homogeneity than others.