Sandblasting is a method used to improve the surface structure of the material by using high pressure. Quartz sand is one of the abrasives used for sandblasting—quartz sand PT. Lamongan DOK contains silica (SiO2) of 83.4%. The method used in this study is the base method. The solvent used is KOH and NaOH with temperature variation of material preparation 600, 900, 1200 oC and variation of extraction time 1, 1½, 2 hours. The results showed that the most optimal variable with NaOH solvent was at the preparation temperature of 900 oC with 2 hours of extraction, and the amount of the extract yield was 28.5%. The following variable is at the preparation temperature of 600 oC with 1.5 hours of extraction, and the amount of the extract yield is 28.3%. Besides that, the optimal variable with KOH solvent is at the preparation temperature of 900 oC with 1.5 hours of extraction, and the amount of the extract Yield is 27.9%. XRD analysis showed that the extract obtained SiO2 in the form of Crystal Cristobalite and Quartz, and the FTIR analysis results detected the presence of O – H alcohol functional groups. It can provide information that sandblasting waste has a reasonably high Silica content, which can be utilized as a product with higher economic value.

The rapid increase in population and land transportation in Kendari City has impacted the availability of green open spaces (GOS), which are crucial for maintaining air quality by absorbing carbon dioxide (CO2) emissions from motor vehicles. This study aims to assess the capacity of GOS in Kendari to absorb CO2 based on different vegetation types. The research employed a descriptive analysis method, with data collected through field observations and secondary sources, including information on GOS area, motor vehicle fuel consumption, and emission factors. The study found that Kendari City requires 17.73 hectares of GOS to absorb the CO2 emissions produced by motor vehicles, while the existing GOS covers 2,562.67 hectares. These indicate that the current GOS is sufficient to perform its environmental functions. Forests in the area absorb 10.292 tons of CO2, parks absorb 1.767 tons, green lanes absorb 27.682 tons, and other GOS areas, including the Kendari Botanical Gardens and sports fields, contribute more diminutive amounts. The results suggest that while Kendari's existing GOS can still manage CO2 emissions effectively, further expansion and optimization of green areas could enhance the City's environmental sustainability. This research provides valuable insights for urban planners and policymakers in Kendari, especially in planning for future GOS development to ensure continued air quality management.