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Nickel is one of the heavy metals that has potential uses in industrial factories. The high demand for nickel causes various efforts to be made to recover nickel from waste. In general, metal recovery is carried out using chemicals in large quantities, so the cost is quite high, and it is harmful to the environment. The recovery of metals using microorganisms, such as bacteria, is quite promising. Therefore, this research will isolate and characterize bacteria from coal ash stockpiles and analyze the potential of these bacteria in nickel recovery through the bioleaching process. Bacterial isolation was carried out by taking a composite sample using the purposive sampling method, and the sample was inoculated into a selective medium for bacteria that play a role in bioleaching. Bacteria that have been isolated will be selected and characterized. Furthermore, these bacteria were tested for their potential in nickel recovery from coal fly ash through the bioleaching process. Bioleaching efficiency is measured to determine the potency of bacteria for nickel recovery. The results of this study showed that eight bacteria were successfully isolated. Characterization results show two gram-negative bacteria and two gram-positive bacteria. Of the eight bacteria, four showed potential for nickel recovery through good growth and higher nickel recovery than the other bacteria. These bacteria are also possibly used for other metal bioleaching processes.

Bioleaching is a technique for reducing the heavy metal content of coal ash by using bacteria, fungi, or yeast. Previous studies in heavy metal bioleaching of coal ash discussed the factors affecting the process, but as yet there is little information on the challenges of using microorganisms. Therefore, this study aimed to obtain comprehensive information regarding the use of microorganisms in heavy metal bioleaching. Heavy metal concentrations in coal ash are low, and the metals are diverse. The components of coal ash are complexes that cannot leach certain heavy metals according to previous studies. These low concentrations and complex components make it difficult to investigate the bioleaching mechanism. The combination of biological and chemical interactions involves various components in this system. The high concentration of iron and heavy metal leached could be toxic for microorganisms. The process is influenced by several factors, such as particle size, pH, and pulp density. Most heavy metal bioleaching studies on coal ash have been conducted on a small scale to control conditions affecting the process. Bioleaching kinetics in coal is a liquid-solid reaction that can be represented by the shrinking core model, which was mainly used in this study. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is an essential element needed by plants. The presence of phosphorus in the environment, especially soil in the form of bound phosphates. This condition can be affected by the acidity of the soil. Available phosphates can be released by phosphate solubilizing bacteria. EF.NAP 1 isolate is a phosphate-solubilizing bacteria that has been successfully isolated from acid soil in the area of the Institut Teknologi Sumatera (ITERA), Lampung, Indonesia, and potency as plant growth-promoting bacteria (PGPB). Based on the results of identification using the 16S rRNA gene, EF.NAP 1 isolates has similarities with Burkholderia territorii. These isolates were able to dissolve phosphate of 104.7 mg/L. P dissolution correlates with the growth phase of bacterial cells. During the phosphate dissolution process, the pH of the medium continues to increase, inversely proportional to the concept in general. The EF.NAP 1 isolate is able to produce six organic acids, i.e, acetic (339.14 mg/L), lactic (260.97 (mg/L), malic (133.24 mg/L), formic (31.52 mg/L), fumaric (19.31 mg/L) and tartaric acids (19.13 mg/L). B. territorii can produce IAA, nitrogenase, siderophore, HCN, chitinase, protease, and cellulose. The potency of B. territorii EF.NAP 1 as phosphate solubilizing bacteria and PGPB properties that have not been reported by others. [ABSTRACT FROM AUTHOR]

Low-cost adsorbents from cassava leaves (CLP) were prepared by simply washing the leaf powder with deionized water. The adsorption of methylene blue (MB) from the aqueous solution was measured in order to examine the adsorbent performance. The effect of the pH of the solution was studied by varying pH from 2 to 10. The kinetics of MB adsorption onto CLP followed the pseudo-second-order kinetic model with a k-value of 0.087907 g mg-1 min-1 and 0.094081 g mg-1 min-1 for CLP before and after washing, respectively. The adsorption isotherm for both adsorbents followed the Langmuir isotherm model with qm values of 178.5 mg g-1 and 243.9 mg g-1. The existence of disturber ions was investigated by adding NaCl into the MB solutions at a variety of concentrations. [ABSTRACT FROM AUTHOR]