Jarosite is an effective scavenger for metals by the chemical formula AFe3(SO4)2(OH)6. In the present article, a comprehensive literature review is performed on the formation, decomposition, and utilization of jarosite. Based on reviewed studies, biological jarosite seeds can shorten the induction period and reduce the temperature limit in the jarosite precipitation. Also, the precipitation process of jarosite is more complete with biological jarosite seeds. The crystallization parameters such as Fe2(SO4)3 concentration, agitation speed, pH and temperature have significantly affected on the morphology and the particles size of jarosite. Decomposition of jarosite is carried out using two different methods thermal and hydrothermal. Jarosite seed is a potential resource, which has to be recycled in a technically feasible and environmentally friendly manner. Besides, it is observed that jarosites have several advantages such as control iron in hydrometallurgy, zinc industry, arsenic removal and other impurities, pigment, nanoparticles, filling materials, adsorption materials, acidic reagent, and catalytic materials.

In the present study, adsorption of Cr(VI) ions from aqueous solutions was investigated and compared under various conditions using two different nano-structured adsorbents, i.e., carbon nanotubes (CNTs) and lowcost activated carbons (AC). Walnut shell, an agricultural solid waste, was used as a raw material for the preparation of ACs. Multi-walled CNTs (MWCNTs) with average diameter of 20 nm and length of about 2 mm were also used for comparison purposes. Adsorption studies were carried out by varying the parameters such as: treatment time, metal ion concentration, adsorbent amount and pH. The adsorption capacities of AC and MWCNT for Cr(VI) ions were measured as 35 and 24 mg g -1 , respectively. The efficiency was observed fairly high at pH = 2-3 for AC and pH = 5-6 for MWCNTs. The adsorption was significantly enhanced by increasing the adsorbent dose up to 0.4 and 0.3 g for AC and MWCNTs, respectively. It was also determined that Cr(VI) adsorption behavior follows both Langmuir and Freundlich isotherms. The content of functional groups, which was obtained by applying the Boehm's method, revealed that phenolic groups are mostly present on the surface of MWCNTs, while basic groups are predominant on the walnut shell AC structures.

No abstract

La disminución de la concentración de iones de hierro de una solución de refinado procedente de la extracción con solvente de cobre es importante para mantener una buena eficiencia de corriente en el proceso de electrolisis. En este estudio, se investigaron los efectos combinados de la “semilla” de jarosita biosintética y Acidithiobacillus ferrooxidans sobre la eliminación de hierro de la solución de refinado de cobre y el efecto del pH. La biosíntesis de “semillas” de jarosita de amonio se realizó de manera eficiente a pH 2 y una concentración de Fe2 + de 50 g·l-1. El porcentaje de eliminación de hierro de la solución de refinado a un pH de 1,5; 2,5 y 5% de dosis de semillas fue de 0,81%, 47,38% y 71,26%, respectivamente. La concentración de hierro en la solución de refinado disminuyó notablemente hasta alcanzar un valor del 71,17% con la incorporación de un 10% en peso de “semilla” de jarosita junto con un 10% V/V de A. ferrooxidans. Esto se debió al aumento en la superficie específica de los sólidos en la solución y a las características magnéticas de A. ferrooxidans que promueven la eliminación de hierro. Se seleccionó un pH 2 y una carga de “semillas” de jarosita del 10% como las condiciones óptimas para la eliminación del hierro de la solución de refinado. Se concluyó que se podría incrementar la recuperación de cobre del refinado biológicamente refinado.

The Lowenstein-Jensen is an egg-based microbiology medium that was designed for selective isolation of Mycobacterium spp. The main inhibitory composition in this medium is a synthetic dye called malachite green. Mycobacterium spp. is resistant to the dye by de-colorization and oxidation of it. Some non-tuberculosis organisms may also overcome this inhibitoryingredient by similar enzymatic activity. In the final inspection of the bone TB culture of a teenage patient, the blind smear revealed the Pseudomonas talus osteomyelitis. Accordingto the present and similar experiences, the preparation of 1-2 blind smears from TB culturenegative specimens taken from sterile sites of the body may unmask mycobacteria with the atypical colony and non-tuberculosis microorganisms.