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Reuse of water in mining helps reduce the volume of tailings directed to dams, avoiding overloads and ruptures, as occurred in Brumadinho, Brazil. Water reuse in mining requires treatment mainly for removing the surfactant substances used. Photo-Fenton and UV/H 2 O 2 showed 96% to 98% degradation results of anionic surfactants within 5 minutes, suggesting this technique is faster than biological systems that can take days. This paper aims to study the degradation of a surfactant used in the flotation process by UV/H 2 O 2 , Fenton, and photo-Fenton oxidation techniques. The compound was characterized by FTIR and MALDI-TOF. In degradation experiments, the variation in reactants concentrations was evaluated with hydrogen peroxide, iron sulphate heptahydrate, and oxalic acid. We used a synthetic solution of surfactant in the reverse flotation of ore with 180 mg/L. The reaction was monitored with TOC analysis and a spectrophotometer throughout the reaction. The UV/H 2 O 2 and

The residue generated in the crystallization stage of the Bayer process to obtain alumina may be used for sodium recovery. The addition of calcium hydroxide (Ca(OH) 2 ) to the residues of the Bayer process may become an alternative study for recovering the caustic soda (NaOH) inserted in the process, so the objective of this work is to utilize the causticization technique in a real residue obtained from the crystallization step of the Bayer liquor. The residue characterized presented 13% Al, so this indicated that there were losses of this element in the Bayer process. Also, the presence of Na 2 C 2 O 4 , Na 2 CO 3 , and NaAlO 2 were observed. The total sodium recovery was 87%, and the best condition for causticization to occur was in the use of a 1:1 molar ratio (Na 2 C 2 O 4 and Ca(OH) 2 ), during 6 h of reaction, and at 80 C, with the conversion of 96% of the organic carbons present in the solution. The causticization was effective in separating sodium from residue in the removal of oxalates, organics, and aluminium, and it provided a reaction that separated oxalates and carbonates that are harmful to the aluminium obtaining process.

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