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The objective of this study was to analyze the use of Spray Drying for concentration and preservation of biosurfactants produced by Bacillus subtilis LBBMA RI4914 isolated from a heavy oil reservoir. Kaolinite and maltodextrin 10DE or 20DE were tested as drying adjuvants. Surface activity of the biosurfactant was analyzed by preparing dilution x surface activity curves of crude biosurfactant, crude biosurfactant plus adjuvants and of the dried products, after their reconstitution in water. The shelf life of the dried products was also evaluated. Spray drying was effective in the recovery and concentration of biosurfactant, while keeping its surface activity. Drying adjuvants were required to obtain a solid product with the desired characteristics. These compounds did not interfere with tensoactive properties of the biosurfactant molecules. The dehydrated product maintained its surfactant properties during storage at room temperature during the evaluation period (120 days), with no detectable loss of activity.

Use of lime to mitigate acid mine drainage is, in general, accompanied by precipitation of iron (Fe) and aluminium (Al) (hydr)oxides which may increase the removal of trace elements from water. This work aimed to evaluate the precipitation of Fe/Al (hydr)oxides to remove rare earth elements (REE) from contaminated water and the stability of precipitates. Two sets of 60-day syntheses were carried out using different Fe/Al/REE molar ratios, for europium (Eu) and holmium (Ho). The pH was periodically adjusted to 9.0, and the stability of the resulting precipitates was evaluated by water-soluble and BCR extractable phases, namely (1) acid soluble, extracted by 0.11 mol L acetic acid; (2) reducible, extracted with 0.5 mol L hydroxylamine hydrochloride; and (3) oxidisable, extracted with 8.8 mol L hydrogen peroxide efficiencies of the water treatments for both Eu and Ho that were higher than 99.9% irrespective to the Fe/Al/REE molar ratios. Water-soluble phases of Eu and Ho were lower than 0.01% of the total contents in the precipitates. Recoveries from precipitates by Bureau Communautaire de Référence (BCR) sequential extractions increased with increasing concentrations of Eu and Ho. Acetic acid extracted higher amounts of REE, but Eu recovery was superior to Ho. Lepidocrocite was formed as Eu concentration increased which decreased its stability in the precipitates.

Effluents from mining activities may have high concentrations of trace elements such as arsenic, rare earth elements (REE) and actinides, mainly in areas where acid mine drainage (AMD) occurs. Use of lime to neutralise AMD also promote co-precipitation of iron (Fe) and aluminium (Al) (hydr)oxides, increasing the removal of trace elements from water. This study aimed to evaluate the efficiency of Fe/Al (hydr)oxides co-precipitation to remove lanthanum (La), cerium (Ce), europium (Eu) and holmium (Ho) from water under laboratory conditions. Two sets of experiments were performed with individual REE solutions containing Eu and Ho. In these cases, Fe(II) and Al sulphates were used at different Fe:Al:REE molar ratios. Two other sets of experiments with Fe(II) and Fe(III) sulphates were performed in a mixed REE solution containing La, Ce, Eu and Ho. To coprecipitate Fe/Al (hydr)oxides, pH's were raised to 9.0 and 6.0 with 5 mol L-1 KOH solution. Soluble contents of Fe, Al and REE were periodically measured in supernatants aliquots. Precipitates were collected at the end of the 60-day incubation period and, then, oven-dried, sieved and characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The stability of REE in precipitates was also assessed by BCR sequential extractions. All treatments presented high REE removal efficiency from water at pH 9.0, but significantly lower at pH 6.0 for Fe(II) treatments. Magnetite precipitation was favoured by lower contents of REE and Al, whereas goethite and lepidocrocite were favoured at higher contents. Segregated phases were not detected for Eu and Ho, but lanthanite and cerianite precipitated at high amounts of La and Ce, respectively. For mixed REE treatments, the mineralogical phases precipitated were mostly poorly crystallised. The presence of magnetite was associated to higher REE stabilities, whereas lepidocrocite decreased the stability as measured by BCR extractions. The presence of segregated phases as cerianite resulted in increased Ce stability, but presence of lanthanite decreased La stability in precipitates.