The purpose of this study was to utilize waste potato skins (PS) and yam skins (YS) in the production of briquettes with rice waste as a binder. The basic materials used to utilize waste, especially potato skins (PS), yam skins (YS), and rice waste. Experiments were carried out by mixing and molding carbon particles made from an equal mass ratio of PS and YS with rice as binders (i.e., 10, 20, 30, 40, and 50%). PS and YS were dried, carbonized at 250°C for 3 hours, and sieved to get sizes of 250 μm. To make compact briquettes, the molded materials were pressed with 5.66 Pa. Several characterizations were analyzed, including compressed density, relaxed density, relaxation ratio, percentage of moisture content, burning rate, percentage of water resistance index, percentage of durability index, specific fuel consumption, the puncture test, and the hardness test. The characterization results showed that the prepared briquettes have good quality, and the best was for 10% of adhesive. The best durability index was for briquettes with 30% of adhesive. The compressed density and water resistance index were optimum when using 40% of adhesive. In general, briquettes with a low amount of adhesive have a high-density value, low moisture content, and a long flammability. This research is expected to convey information regarding how to reuse rice waste as an adhesive for briquettes.

The use of disposable primary batteries causes environmental pollution due to the lack of battery waste treatment facilities, so it is necessary to handle the problem by making bio-batteries from orange peel and tamarind. The purpose of this study is to know the influence of good electricity on variations of the combination of orange peel and tamarind. The novelty of this study is (1) the use of biomass combination of orange peel and tamarind as bio-battery electrolytes and (2) comparison of orange peel to tamarind. The method used in this study is by experimenting with a mixture of sweet orange peel and tamarind made into pasta and put in a used battery. The results showed that bio-batteries with a variation of 25% orange to tamarind had the highest voltage and the most powerful electric current. This happens because the ion content in the variation is not concentrated so it is easy to move widely. In conclusion, bio-batteries with a mixture of orange peel and acid are the best variation of 25% orange peel against tamarind. The study is expected to reduce the use of chemicals in batteries and reduce disposable battery waste.

This study replaced fly ash with palm oil fuel ash (POFA) in geopolymer paste and mortar. The alkaline activator was a mixture of sodium silicate solution and sodium hydroxide solution with a ratio of 2.5. Three variables were evaluated: the raw material combination (100% fly ash and 25% POFA substituted to fly ash), the mass ratio of raw material to alkali activator (60/40, 65/35, and 70/30), and NaOH molarity (8 M and 10 M). The geopolymer mortar was utilized based on the highest compressive strength of geopolymer paste. The ratio of fine aggregate to binder was 65 to 35. The result showed that the compressive strength of geopolymer paste increased as NaOH molarity increased. 25% substitution of POFA for fly ash increased the compressive strength of geopolymer paste from 12.0% to 27% at 28 days. The raw material/ alkali activator ratio of 65/35 indicated the highest compressive strength. The POFA replacement for fly ash had a longer setting time than 100% fly ash. The compressive strength ratio of mortar to the geopolymer paste was 0.66 and 0.59 for the 65/35 and 70/30 ratios of raw material to alkali activator, respectively.

This research was conducted to determine the effectiveness of the method of learning the electroflotation process with a variety of stainless steel and copper electrodes and the voltages and voltages used. The experiment was carried out by treating domestic wastewater with the electroflotation method at various voltages of 6; 9; 12; 15; and 18 volts and variations of electrodes A, B, and C. The elements of the dispersed substance in the water medium, the pH level, and temperature in the water sample are measured first, then measured again to find out how much influence electroflotation has in separating pollutants. The application of learning is done by providing pretest questions, learning videos, and posttests. The results showed that sample A was good because it had an average value in the decrease in TDS as well as the temperature of the solution. While the results of the implementation of demonstration videos are effective, the score is not significant because it is likely that students already understand the concept as well as network factors. This research is expected to provide solutions to the problem of domestic oil-tainted water and improve the understanding of vocational school students about the concept of electro flotation to clear water. Keywords: copper, electro flotation, stainless steel, teaching clears water