Phosphorus (P) is an essential macronutrient that plays a pivotal role in the growth of plants, which, when insufficient, may adversely affect crop yields. Phosphate is directly linked to the world’s population growth, as agriculture plays a crucial role as an essential human activity for sustaining life and development. Population growth tends to amplify environmental pressures, impeding progress towards a more sustainable future, including the demand for food, housing, and infrastructure. In this context, the importance of NPK (nitrogen, phosphorus, potassium) fertilizers for agriculture and food production should be highlighted. The phosphorus comes from the mineral apatite, which is usually concentrated by froth flotation before being processed for fertilizer production.

Flotation is one of the most fundamental unit operations in mineral processing, a technique that relies on the physicochemical properties of minerals and chemical reagents (depressants, frothers, collectors) to selectively separate valuable minerals from the gangue by exploiting their differences in surface properties. In recent years, there has been a reinforcement of regulations and pressures to reduce chemical toxicity, increase biodegradability, and lower environmental impact. Therefore, the use of the term “green reagents” has increased substantially. However, despite its widespread usage, the notion of a green reagent for flotation remains ambiguous, under-defined, and contested. 

This thesis was written with the objective to answer the following questions: Q.1.: “What is a green reagent for flotation?” This question requires methodological reflection because the definition of “green” is not purely technical or chemical, but it is also a discursive, industrial, and contextual construction. To fully understand this concept, this study employs a triangulated research design combining qualitative data (document analysis, framework analysis, and grounded theory elements) and quantitative data (mechanistic, causal, and diagnostic laboratory flotation tests). The second research question is related to the past of the main topic of this work, which is focused on apatite flotation: Q.2.: “What is known until nowadays about green collectors for phosphate flotation?” This question was primarily used to map the main published knowledge on environmentally friendly collectors. The third research question is about the updated present of apatite flotation: Q.3.: “What are the main green collectors applied commercially worldwide for apatite flotation, and how are they conceptually classified?” This question aims to compare market products using qualitative and quantitative analysis, specifically for LKAB apatite ore. Future work will focus on applying different molecules and studying their mechanisms in apatite flotation, comparing their effects on performance (grade and recovery).