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As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to improve flotation performance of fine and ultrafine particles, there is still much more to be done. In this paper, the effects of nano-microbubbles (nanobubbles and microbubbles) on the flotation of fine (−38 + 14.36 μm) and ultrafine (−14.36 + 5 μm) chalcopyrite particles were investigated in a laboratory scale Denver flotation cell. Nano-microbubbles were generated using a specially-designed nano-microbubble generator based on the cavitation phenomenon in Venturi tubes. In order to better understand the mechanisms of nano-microbubble enhanced froth flotation of fine and ultrafine chalcopyrite particles, the nano-microbubble size distribution, stability and the effect of frother concentration on nanobubble size were also studied by a laser diffraction method. Comparative flotation tests were performed in the presence and absence of nano-microbubbles to evaluate their impact on the fine and ultrafine chalcopyrite particle flotation recovery. According to the results, the mean size of nano-microbubbles increased over time, and decreased with increase of frother concentration. The laboratory-scale flotation test results indicated that flotation recovery of chalcopyrite fine and ultrafine particles increased by approximately 16–21% in the presence of nano-microbubbles, depending on operating conditions of the process. The presence of nano-microbubbles increased the recovery of ultrafine particles (−14.36 + 5 μm) more than that of fine particles (−38 + 14.36 μm). Another major advantage is that the use of nano-microbubbles reduced the collector and frother consumptions by up to 75% and 50%, respectively. Keywords: Nanobubbles, Nano-microbubble, Bubble size distribution, Chalcopyrite, Froth flotation, Fine particles

Researchers have recently focused their attention on emerging contaminants (ECs) in wastewater because they pose serious health and environmental risks. Because ECs are persistent in the environment and have the ability to disrupt the physiology of target receptors, they have been labeled as contaminants of recent environmental concern. For removing various ECs, a variety of treatment technologies have been developed, including biological, chemical, and physical methods. However, no single technology can currently effectively remove ECs, whereas hybrid systems have consistently proven to be more effective. Furthermore, the majority of existing technologies are energy and resource intensive, as well as expensive to maintain and operate. Furthermore, the majority of advanced treatment technologies that have been proposed have yet to be evaluated for large-scale feasibility. Some ECs, particularly pharmaceuticals and pesticides, were found to be significantly removed using a hybrid technique that included ozone/UV and granular activated carbon (GAC). Besides, the removal of effluent parameters (TDS, COD, TOC) was enhanced through the GAC surface oxidization as a catalyst with NaOH before the process and by ozone within the procedure as well. [ABSTRACT FROM AUTHOR]

Treatment of organic leachate is one the most controversial topics around the world which led this study to assess the efficiency of the combined oxidation and adsorption treatment (COAT) process in the treatment of forest polluting site (FPS) leachate by considering local experiments. The removal of effluent parameters (TDS, COD, BOD) was enhanced by oxidizing the GAC surface as a catalyst with NaOH before the process and by ozone within the procedure as well. comparison between COAT process and ozone-GAC was investigated based on variation in ozone dose, H2O2 and pH. Assessing the interacting effect of operating variables (i.e., ozone concentration, GAC density, reaction time and pH) provides valuable information for optimization. Response surface methodology (RSM) and for better prediction, another modeling tool, artificial neural networks (ANN), were employed. Moreover, the results of both software were compared and ANN showed a higher R2 of 0.908, 0.923, and 0.919 for TDS, COD, and BOD respectively in contrast with RSM (R2: TDS = 0.8538, COD = 0.9105, BOD = 0.8108). The optimized model's circumstances are the reaction time of 30.77 min, ozone dosage of 141.29 mg/l, pH of 7.2, and the GAC density of 1.29 gr/cm3 with the predicted removal percentage of 51.63%, 62.84%, and 56.13% for TDS, COD, and BOD respectively. Meanwhile, in the experimental situation among the various methods, the COAT process by the removal percentage of TDS = 59.47%, COD = 68.37%, and BOD = 67% showed proper efficiency. [ABSTRACT FROM AUTHOR]

Concrete corrosion has a great economic impact on many worldwide projects especially in corrosive environments such as municipal sewer systems. Many different factors can cause corrosive attacks on concrete structures that can be categorized into two main groups, chemical sulfuric acid attack, and microbial corrosive process via producing biogenic sulfuric acid (BSA). The present work aimed on assessing the sulfur concrete durability in sewerage environment and investigating the effects of microbial corrosion on this type of concrete. In this study, two tests were conducted including sewer concrete pipe in situ, and experimental tests on cubic samples. For biological tests, this bacterium was chosen for performing laboratory tests since the presence probability and population of Thiobacillus thiooxidans microorganism in domestic sewer is higher than other species. Results showed that sulfur concrete is considerably resistant to severe acid attack, but is less resistant to microbial corrosion attack than chemical corrosion especially against sulfur oxidizing bacteria. This is completely different in Sewer environment, because the microbial attack is limited by some factors such as pH variety and other bacteria presence competition. [ABSTRACT FROM AUTHOR]

Cyanide, as one of the most toxic pollutants existing in the gold mine tailing dams, threatens human health and other species life. The main objective of this study was to simulate the oxidation of cyanide from mineral effluent of the Moteh Tailing Dam (Iran), as a method for removing cyanide. We employed PHREEQC software to model the oxidation of cyanide using calcium hypochlorite (Ca(OCl)2) and sodium hypochlorite (NaOCl). The results indicated that Ca(OCl)2 and NaOCl concentrations, as well as pH, influenced the oxidation of cyanide. The model was run in the constant temperature of 12°C and pH between 12 to 13. By rising Ca(OCl)2 concentration from 0.71 to 1.43 g/l and NaOCl concentration from 1.72 to 5.18 g/l, the removal rates of cyanide increased from 97.01% to 99.20% and 95.46% to 95.90%, respectively. The coefficient of determination (R2), index of agreement (IA), and Nash- Sutcliffe efficiency (E) were used to assess the predicted removal rate of cyanide in comparison with experimental observations, which demonstrated a suitable agreement: Ca(OCl)2 = 0.71 mg/l, R² = 0.97, IA = 0.91 and E = 0.73; Ca(OCl)2 = 0.85 mg/l, R² = 0.99, IA = 0.99, E = 0.96; Ca(OCl)2 = 1.43 mg/l, R² = 0.97, IA = 0.92, E = 0.79; NaOCl = 1.72 mg/l, R² = 0.97, IA = 0.92, E = 0.74; NaOCl = 3.45 mg/l, R² = 0.91, IA = 0.91, E = 0.71; NaOCl = 5.18 mg/l, R² = 0.96, IA = 0.91, E = 0.77. [ABSTRACT FROM AUTHOR]

One of the main challenges in the copper oxide processing industry is implementation of a flotation method to reduce operating costs. Sulphidising flotation is the most common used technique in which a sulphidisation agent is used to sulphidise the surface of the oxide minerals. In this research, the mentioned technique was used sequentially for the concentration of silicate-carbonate ore containing 3.1% Cu (malachite). The presence of 39% Cu in -38 μm size fraction (fine particles) of feed led to poor grades and recoveries in the initial tests. The addition of sodium sulfide and subsequent flotation at three sequential stages was identified as a successful operational initiative to solve this problem in the following tests. The dosages of 1500, 1567 and 100 g/Mg of sodium silicate, sodium sulfide and potassium amyl xanthate, respectively, the conditioning time of 5 min for sulphidisation and pH=9.72 were chosen as optimum operational conditions using central composite design (CCD) method of experiments design. The rougher concentrate with 9.28% grade and 81.15% recovery was obtained under these conditions. The grade of obtained concentrate was reached to 24% in the cleaner step. The total recovery of both steps was over 74%. [ABSTRACT FROM AUTHOR]