Chemical reagents used in traditional mineral processing can be toxic and hazardous for the environment. Therefore, the use of biotechnological methods is becoming increasingly important. Great hopes are being placed in the use of microorganisms for bio-beneficiation of raw materials. However, assessment of adhesion abilities of bacteria onto minerals surface as well as biosorption of metals are essential steps before designing final process of each ore beneficiation. The main aim of this work was an investigation of biosorption of Cd and Mg, as well as adhesion abilities of five microorganism species with minerals included in the natural mixture of phosphate ore form Djebel Onk, Algeria. The ore, due to its unique composition, created conditions for adhesion of all five tested microbial strains onto apatite surface during incubation at pH 3. Moreover, Rhodococcus erythropolis CD 130, Pseudomonas fluorescens and Escherichia coli adhered distinctly onto apatite surface during incubation at pH 7. Incubation lasting 20 min at pH 4-6 created the most favorable conditions for biosorption of metals by B. subtilis and adhesion of cells. In case of C. albicans, biosorption of metals as well as adhesion of cells onto the mineral surface were more effective after longer time and in a wider pH range.

Mining and processing phosphate ore are among the essential branches of the economy in some developing countries, including Algeria. Conventional ore beneficiation methods can harm the environment by consuming tremendous amounts of water resources (during washing and flotation), potentially hazardous chemicals, and thermal energy. Mine water contains toxic metals that, when released, interfere with environmental functioning. Therefore, in line with environmental needs, conventional methods should be gradually replaced with safe biotechnological processes. This study aimed to investigate the biosorption and adhesion abilities of native microorganisms isolated from Djebel Onk ore (Algeria). The examined bacterial strains differed in their metal accumulation efficiency. The incubation of phosphate ore with the native strain Bacillus HK4 significantly increased the recovery of Mg and Cd (at pH 7, 8147.00 and 100.89 µg/g−1, respectively). The HK4 strain also revealed better adhesion to the ore particles than the reference strain of Bacillus subtilis. Thus, biosorption could be more effective when using the native HK4 strain, which can remove Cd and/or Mg over a pH 4–10 range. Moreover, concerning the unique adhesion capacity of HK4, the strain can be considered in the design of bioflotation methods, as well as in the development of an eco-friendly method of ore and post-flotation waste beneficiation.

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