The use of flocculants to control turbidity in placer mining effluents

Presented to the Faculty of the University of Alaska in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCEIn this study, two placer mine discharge waters of different characteristics were tested in order to determine the applicability of organic polymer flocculants to achieve reduced levels of turbidity. The water samples from both mines were characterized both as to their chemical and physical properties. The jar test was employed to establish the optimum operation conditions of the flocculation process. The best results were obtained employing a cationic polymer Superfloc 340 produced by American Cyanamid Company. The optimum dosage for water samples from both mines were 15 ppm and 40 ppm respectively. Optimum agitation time was within the range of 3 to 9 minutes depending on the agitation rate and the pulp density of water sample. The utilization of settling ponds, in conjunction with flocculation is believed to be a practical method to control the turbidity level of placer mine discharge water

Effect of chitosan biopolymer and UV/TiO2 method for the de-coloration of acid blue 40 simulated textile wastewater

The purpose for this study is to de-color C.I. Acid Blue 40 simulated textile wastewater using chitosan and UV/TiO2 system. The methodology is to use chitosan biopolymer and UV/TiO2 to degrade textile wastewater and to measure the color removal by UV-visible spectrophotometer. The operational parameters are chitosan, TiO2, pH and reaction time. From the laboratory investigations, different efficiencies were observed according to different removal operating levels. Single chitosan of 2500 ppm dose was used to remove Acid Blue 40 textile wastewater and to obtain a better efficiency. TiO2 alone with UV light was also used with the dose of 2500 ppm to obtain a better efficiency. In acidity, both chitosan and TiO2 obtain better efficiencies under pH 4 operational condition. The best combination for UV/TiO2 system to de-color the 50 ppm Acid Blue 40 textile wastewater was TiO2 2500 ppm concentration with UV illumination at pH 4. The result shows that the de-colorization efficiency reached 98.8% elimination after 210 min of reaction time.Keywords: Chitosan biopolymer, UV/TiO2, Acid Blue 40, textile wastewater, spectrophotometerAfrican Journal of Biotechnology Vol. 9(34), pp. 5575-5580, 23 August, 201

Synthesis of Ultramarine from Reservoir Silts

Ultramarine blue was synthesized by using reservoir silts as a major raw material to replace traditional kaolin clay. The reservoir silts were pretreated to collect the fines, in which the main mineral composition is illite clay. The fine part was mixed with sodium carbonate, sulfur, and activated carbon, and calcined at 800°C for 8 h. The products were examined by X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) to identify the mineral phases and particle morphology. The color characteristics were measured according to the CIELab system. Brilliant blue ultramarine powders were successfully synthesized with a chroma of 52.4, which is competitive with the commercial ultramarine

Thermochemical Characterization of Rice-Derived Residues for Fuel Use and Its Potential for Slagging Tendency

Rice is the most important cereal in Asia. However, it also results in the generation of large quantities of rice-derived residues (i.e., rice straw and rice husk). Due to the residues richness in lignocellulosic components, they potentially have considerable value in material and/or energy production without illegal burning in open fields. This work focused on investigating the thermochemical properties and inorganic/metal element contents of rice straw and rice husk. The former included proximate analysis, calorific value, thermogravimetric analysis (TGA) and energy dispersive X-ray spectroscopy (EDS). The latter covered the ten elements most relevant to their slagging/fouling indices. The results showed that they are suitable for energy use as biomass fuels, but rice husk was superior to rice straw because of the high silica content in the rice husk and the significant contents of potassium, sulfur and phosphorus in the rice straw. Using several slagging and fouling indices, the evaluation results were also consistent with their contents of inorganic elements or oxides. To increase the fuel properties of rice-derived residues, they could be pretreated with alkaline leaching, thus causing lower emissions of particulates and reduced slagging tendency when co-firing them with coal in industrial boilers

Sustainable Material Management of Industrial Hazardous Waste in Taiwan: Case Studies in Circular Economy

In recent years, the rapid economic development in Taiwan has resulted in greater complexity in handling industrial hazardous waste. The main aim of this paper was to present a trend analysis of the online reported amounts of industrial hazardous waste from the official database over the past decade (2010–2020). In addition, this study focused on the environmental policies and regulatory measures for the mandatory material resources from industrial hazardous waste according to the promulgation of the revised Waste Management Act. It was found that the annual reported amounts of industrial hazardous waste ranged from 1200 thousand metric tons to 1600 thousand metric tons, reflecting a balanced relationship between the industrial production and waste management. Based on the principles of resource recycling and circular economy, some case studies for specific types of industrial hazardous waste (including spent acid etchant, spent pickling liquid, and spent dimethyl formamide-contained liquid) were compiled to echo the government efforts in sustainable material management. In Taiwan, recycling amounts in 2020 were recorded up to 92,800, 130,460, and 54,266 metric tons, respectively. It was suggested to be a successful circular economy model in the printed circuit boards, steel/iron processing, and synthetic leather industries. In order to effectively reduce the environmental loadings and conserve material resources from industrial hazardous waste, some recommendations were also addressed to provide for the policy makers, environmental engineers and process manager

Effect of Alkaline Pretreatment on the Fuel Properties of Torrefied Biomass from Rice Husk

Lignocellulosic biomass from rice husk (RH) is a renewable resource for fuel production, but it could pose ash-related challenges. This work focused on investigating the effects of pretreatment at different sodium hydroxide (NaOH) concentrations (i.e., 0.0, 0.25, 0.50, 0.75 and 1.00 M) on the calorific values and ash contents of treated RH products, and also finding the optimal torrefaction conditions. The results showed that alkaline pretreatment by sodium hydroxide (NaOH) reduced the ash content in the RH samples by over 85 wt%. Due to its relatively excellent calorific values and low ash content, the RH sample with 0.25 M NaOH pretreatment (i.e., RH-25) was chosen as a starting feedstock in the subsequent torrefaction experiments as a function of 240–360 °C for holding time of 0–90 min. In addition, the surface properties by scanning electron microscopy—energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier-transform infrared spectroscopy (FTIR) were also used to observe the elemental compositions preliminarily. Based on the fuel properties of the torrefied RH products, the optimal torrefaction conditions can be found at around 280 °C for holding 30 min. As compared to the calorific value of the RH-25 (i.e., 18.74 MJ/kg) and its mass yield (i.e., 0.588), the calorific value, enhancement factor and energy yield of the optimal product were 28.97 MJ/kg, 1.55 and 0.91, respectively. Although the resulting product has a high calorific value like coal, it could have slight potential for slagging and fouling tendency and particulate matter emissions due to the relatively high contents of silicon (Si) and sodium (Na), based on the results of EDS and FTIR

Tungsten Recovery from Spent SCR Catalyst Using Alkaline Leaching and Ion Exchange

The recovery of tungsten (W) from a honeycomb-type spent selective catalytic reduction (SCR) catalyst using an alkaline leaching–ion exchange method was investigated. Spent SCR catalyst mainly consists of TiO2 and other oxides (6.37% W, 1.57% vanadium (V), and 2.81% silicon (Si), etc.). The ground catalyst was leached at the optimal conditions, as follows: NaOH concentration of 0.3 kg/kg of catalyst, pulp density of 3%, leaching temperature of 70 °C, particle size of −74 μm, and leaching time of 30 min. In this study, the leaching rate values of V and W under the above conditions were 87 wt %, and 91 wt %, respectively. The pregnant solution was then passed through a strong base anion exchange resin (Amberlite IRA900). At high pH conditions, the use of strong base anion exchange resin led to selective loading of divalent WO42− from the solution, because the fraction of two adjacent positively-charged sites on the IRA900 resin was higher and separate from the coexisting VO43−. The adsorbed W could then be eluted with 1 M NaCl + 0.5 M NaOH. The final concentrated W solution had 8.4 g/L of W with 98% purity. The application of this process in industry is expected to have an important impact on the recovery of W from secondary sources of these metals

Separation of Valuable Metals in The Recycling of Lithium Batteries via Solvent Extraction

With the development trend and technological progress of lithium batteries, the battery market is booming, which means that the consumption demand for lithium batteries has increased significantly, and, therefore, a large number of discarded lithium batteries will be generated accordingly. Solvent extraction is a promising approach because it is simple. Solvent extraction is low in time consumption and is easy to industrialize. This paper is focused on the selective recovery of cobalt (Co), nickel (Ni), and manganese (Mn) contained in leachate obtained by digesting a cathodic material from spent lithium batteries with hydrochloric acid. After leaching the cathodic material, Mn was selectively extracted from leachate by using solvent extraction with D2EHPA diluted in kerosene in an optimized condition. Afterward, Co was extracted from the Mn-depleted aqueous phase using Cyanex272 diluted in kerosene. Finally, the raffinate obtained via a stripping reaction with H2SO4 was used in the Ni extraction experiments. Cyanex272 extractant was employed to separate Ni and Li. The process can recover more than 93% of Mn, 90% of Co, and 90% of Ni. The crucial material recovered in the form of sulfuric acid solutions can be purified and returned to the manufacturer for use. This process proposes a complete recycling method by effectively recovering Mn, Co, and Ni with solvent extraction, to contribute to the supply of raw materials and to reduce tensions related to mineral resources for the production of lithium batteries

Separation of Cobalt, Samarium, Iron, and Copper in the Leaching Solution of Scrap Magnets

With the growing awareness of protecting the urban environment and the increasing demand for strategic materials, recycling of SmCo magnets has become imperative. This paper provides a series of methods regarding the available hydrometallurgical technologies for recycling scrap magnets. This study aimed to recover samarium (Sm), cobalt (Co), copper (Cu), and iron (Fe) from acid leachate of SmCo scrap by using precipitation and ion exchange. IRC748 showed a good adsorption capacity for Fe and Cu. Elution tests were conducted using sulfuric acid at the concentration of 2N as eluents. Precipitation was performed first using a selective chemical precipitation method, and the Sm was first precipitated as a sodium samarium sulfate powder. Then, the samarium-deprived solution was placed in the beaker, and the addition of oxalic acid promoted cobalt oxalate precipitation. Furthermore, the leachate, which is rich in Cu and Fe, was mixed with oxalic acid to obtain the copper oxalate precipitation. This study successfully recovered SmCo magnets through ion exchange and precipitants

Production of Mesoporous Magnetic Carbon Materials from Oily Sludge by Combining Thermal Activation and Post-Washing

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, the preparation experiments were performed at 800–900 °C. From the pore analysis of the CC products, it indicated an increasing trend, as the BET surface area greatly increased from about 1.0 to 44.30 m2/g. In addition, the enhancement effect on the pore properties can be consistently obtained from the acid-washed CC products because the existing and new pores were reformed due to the leaching-out of inorganic minerals. It showed an increase from 32.27 to 94.45 m2/g and 44.30 to 94.52 m2/g at 850 and 900 °C, respectively, showing their mesoporous features. These porous and iron-containing features were also observed by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). In addition, the adsorption removal of total organic carbon (TOC) in the raw wastewater, by the CC product, showed its high performance (>80%)