No abstract

Indonesia is one of the largest tin producers in the world. The by-products of processing tin ore in the form of tailings are not used properly. Based on several studies, tin tailings have high levels of silica. In this paper, a silica purification study from tin tailings is proposed using a solid-state method at different pH. The purity of silica in this paper is determined by XRF and XRD analysis. This research is expected to increase the economic value of tin tailings, which can be utilized in various applications.

The presence of dyes in wastewater is one of the main problems in wastewater treatment. Wastewater containing dyes can damage the ecosystem because it can block sunlight into the water and is often accompanied by toxic materials. This paper proposes an alternative method to decolorize dyes in water using CuO as a Fenton-like catalyst, especially for wastewater contaminated by methylene blue dye. The Fenton method is an advanced oxidation process method with a radical group of H2O2 acting as the primary decolorizing agent. By measuring the concentration using a UV-Vis spectrophotometer, we found that the proposed decolorization method effectively degraded the color of methylene blue. To understand the decolorization mechanism, we investigated the reaction kinetics of the decolorization process. We found that compared to the pseudo-first-order and second-order reaction kinetics models, the BMG model had higher accuracy and conformed to the color concentration degradation curve.

As a maritime country, shrimp commodity production in Indonesia is very high and continues to increase. However, because shrimp is a perishable food, we need a detection device. This is because conventional methods that are widely used by the community in detecting freshness of shrimp are only based on the smell. Of course, this is a problem when shrimp are packed in closed containers. In this paper, a method for detecting shrimp is proposed using the Melastoma malabathricum L. - based label indicator. The high content of flavonoids in the extracts allows the changing the colour of the label from red to grey due to the interaction between the label with the OH- group that arises from the shrimp spoilage process. The colour that appears on the label indicator will correlate with the level of shrimp freshness. By increasing detection effectiveness, the classification is performed using the nearest-neighbours algorithm, which is equipped with an image processing mechanism in the form of colour quantization. There are four classifications used to express the quality of shrimp, namely "acceptable," "just acceptable," "unacceptable," and "more unacceptable." The accuracy of applying this method is 71.9%, with the majority of detection errors occurring in the "acceptable" class. Based on these results, it can be stated that the label indicators prepared in this study are very promising to be developed into intelligent packaging components.

CuO-doped SnO2 nanoparticles were successfully synthesized using biosynthetic methods with the pelawan leaf extract. This method is a modification of the sol-gel process by utilizing antioxidant compounds from the leaf extract as a trap-matrix for tin oxides. This research was conducted based on variations in CuO doping. The characteristics of tin oxide observed in this study were a phase, crystallite size, and crystallinity, which determined based on x-ray diffraction method. It is expected that the method proposed in this study can be developed to synthesize SnO2 nanoparticles that are environmentally friendly.