[A-HW18] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW18-P02] Vinasse potassium recovery with zeolite for use as a slow-release fertilizer

*Juliana Gardenalli de Freitas¹, Flávia Oliveira Damaceno¹, Fernanda Kaori Kuriki¹, Mirian Chieko Shinzato¹, Reginaldo Bertolo², Ricardo Hirata² (1.Universidade Federal de São Paulo, 2.Universidade de São Paulo)

Keywords:vinasse, zeolite, groundwater contamination, fertilizer, adsorption

Vinasse is an acidic liquid waste generated during sugar and alcohol production, rich in organic matter, potassium, and other nutrients of interest to agricultural production. Because of its high nutrient content, it is commonly applied directly into the soil as a fertilizer for sugar cane. This practice is very common in Brazil, but can cause severe soil and groundwater contamination. For example, it contains hundred times more organic matter than raw sewage. Therefore, recovering the nutrients from vinasse to be reused as fertilizers can decrease the impacts caused by soil and groundwater contamination. A sustainable alternative is to use minerals with high retention capacity, such as zeolites, to retain the nutrients, and then apply them as slow-release fertilizers. Zeolites enriched with potassium from the vinasse can be applied into the soil as a slow-release fertilizer, minimizing nutrients loss by leaching. Therefore, this study evaluated the potassium sorption capacity of zeolite. The zeolite used was originated from Cuba, and composed of 67.5% clinoptilolite, 20% de mordenite, and 12.5% muscovite. The vinasse contained 2160 mg L^-1 of potassium and pH around 4.5. The potassium sorption capacity was initially determined using synthetic solutions prepared with KCl in batch tests (0.5 g of zeolite in 25 mL of potassium solution with concentrations ranging from 100 to 400 g mL^-1 K⁺, agitated for 60 min). Then, column tests were performed simulating vinasse flow through the zeolite. For ten hours, vinasse (6 L) was percolated through 50 g of zeolite. The batch tests results were analyzed according to adsorption models (Langmuir and Freundlich) and confirmed a high affinity of the zeolite sample to potassium, with maximum sorption of 20.60 mg K⁺ per gram of zeolite. In the column tests using vinasse, the highest adsorption rate was 44 mg g^-1. This shows that the zeolite has a high capacity of retaining potassium, even in the presence of other ions. Future tests will evaluate potassium release from the enriched zeolite. The authors thank the São Paulo Research Foundation (FAPESP) for support through grants 2020/15434-0 and 2022/00652-7 and the scholarship from the National Council for Scientific and Technological Development (CNPq).