Mine acid drainage (MAD) is a primary environmental problem caused by mining activity. The main characteristics of MAD are extremely low pH level (1.5–4.0), as well as content of sulfate and a number of heavy metals and metalloids that can destroy vegetation, accelerate erotion, and disrupt land ecosystem balance. The objective of this research was to process MAD by improving pH level and lowering iron and manganese content in MAD by Lactobacillus casei and Dekkera bruxellensis mixed culture. MAD Neutralization test was conducted on SMSs media with MAD concentration variations of 10, 15, 20 and 25 (%;v/v), and contact time variations of 48, 96, 144, and 192 (hours). The MAD neutralization test by Lactobacillus casei and Dekkera bruxellensis mixed culture occurred best at 10% concentration (v/v) with contact time of 96 hours. The pH improvement reached up to 6.20 with iron metal efficiency removal at 32.47% and manganese metal up to 24.94%. MAD neutralization test revealed that the best contact time variation is at 96 hours. At this contact time, the pH level was increased to 6.17 with iron metal removal efficiency at 31.17% and manganese metal removal at 25.43%.
This research was conducted to overcome the Cu2+ heavy metal pollution in the environment through a biotechnological approach with heavy metal sorption process by microalgae beads. Biosorbent in form of beads was produced from Chlorella sorokiniana, Monoraphidium sp., and Scenedesmus obliquus tropical microalgae mobilized with Naalginate polymer. The sorption process is observed on a controlled batch culture with variations of temperature (25, 35, and 45 °C), and observation periods (200th, 220th, 250th, 270th min) as contact time. The absorption efficiency on each temperature variation reaches more than 90%, but the highest absorption efficiency rate is at 92.20% on 35 °C temperature and 200 minutes of contact time. Biosorbent beads with 2–3 mm of diameters show the best sorption ability than the 3–4 mm and 4–5 mm ones. Sorption process is also evident with the existence of intensity alteration on amide, ketone, and sulfhydryl function groups which were consistently weakened until the end of the sorption process. The beads utilized in this research are potentially reusable as biosorbent. Thus, further examination is required to acknowledge the maximum reutilization rate of the beads as biosorbent on heavy metal absorption process.
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