Papers by Keyword: Leaching

Abstract: The performances of leaching-upflow blanket filter (UBF) anaerobic digestion for biogas production of kitchen waste was investigated. To find out the process parameter variations of acidification phase and the methane production performance of methanogenic phase, kitchen waste from division of environment sanitation management of Changzhou was used as feedstock. The results show that the ammonia in anaerobic system cumulated continuously throughout the digestion; pH value maintained at7.6; At first the value of COD ranged from 20000 mg/L to 140000 mg/L to the final UBF water 10000mg/L to 12000 mg/L; Volatile fatty acid (VFA) reduced to 150mg/L with the increase of the days; total nitrogen increases first and then decreases, finally, it keeps at 1600 mg/L; The concentration of alkalinity increased slightly; biogas production is stable, The rate of gas generation is above0.30 m3/kgCOD . These results provide a proof of the feasibility for kitchen waste anaerobic methane fermentation.

Abstract: We studyed on the “the binding capacity of EPS and Fe³⁺”,“the promoting effect experiment of EPS-Fe³⁺ to the leaching of Cr, Pb”and the “distribution characteristics of heavy metals in EPS,inside and outside cells”.Proved that large molecular EPS (MT) and Fe³⁺ tend to form a stable complex EPS (MT)-Fe³⁺. Unit mass of macromolecular EPS binding ability to Fe³⁺ is 10.7mg/mgEPS.And with the addition of EPS (MT)-Fe³⁺ complex, Cr, Pb in sludge by bioleaching removal rate increased by 1.48, 1.25 times.The distribution characteristics of heavy metal ions in the cell into three types: type EPS, intracellular type, balance type.

Abstract: In order to investigate the possible pollution status in soils and underground water caused by arsenic in coal gangue, samples from Inner Mongolia mining area were collected and dynamic leaching experiments were conducted in laboratory to study the leaching level of arsenic and its migration in soils under different rainfall conditions. Results indicated that, concentration of arsenic in leachate is far below the third grade of National Environmental Quality Standards for groundwater; while concentrations of arsenic increased with the decreasing of pH of rainfalls. Concentrations of arsenic are in the descending trend with the increasing depths of soils after leaching; the changes of pH in leachate and soil are relevant to the initial pH value of leachate.

Abstract: the carbide can be used as of Calcium carbide residue is a kind of industrial waste produced in the preparation of acetylene gas from hydrated calcium carbide, and the main component of the calcium carbide residue is calcium hydroxide. In this paper, the production of calcium carbonate by calcium carbide residue was studied, and carbide slag and ammonium bicarbonate was the main materials. The impurity in the carbide slag was removed through the leaching reaction, and the calcium carbonate was prepared by liquid-liquid reaction. The different reaction conditions which had an influence on the grain diameter of the product in the process of leaching and carbonation reaction were also investigated. The characteristics of materials and products in the experiment were tested by XRD, SEM and laser particle size instrument. The results showed that the calcium carbide residue after appropriately treated can be used as the raw materials to prepare calcium carbonate in different particle size.

Abstract: In this study, an iron ore was investigated with high content of phosphorus and sulphur about 1.09% and 1.4%, respectively. The grade of Fe is about 30%, which is mainly composed of siderite, about 23.40% of iron is existed in the form of silicate, such as chlorite, canbyite, and a small amount of pyrite, magnetite. The phosphorous mainly occurred as apatite, which is close united with the phase of iron, and the sulphur mainly comes from pyrite. According to the mineralogy analysis of run-of-mine, acid leaching and reduction roasting with sodium carbonate is used for the high efficiently dephosphorization and desulfurization. Magnetic tube experiment after reduction roasting with sodium carbonate, an iron concentrate with 84.5%, Fe was produced with 69.7% relative recovery as a result of magnetic tube experiment carried out with 3A electric current.

Abstract: The industry of biomass power in China has been growing tremendously in recent years, but it is faced with many challenges now. The low efficiency of straw combustion in the boiler results in that the carbon content in the fly ash could reach 15~30%. The ash is also rich in silica, potassium, calcium and has a lot of microelements. A kind of fly ash from a biomass power plant mainly uses corn straw as feedstock was studied. XRF analysis showed that the contents of K₂O, CaO and MgO in the ash were 7.22%, 13.61% and 7.22%, respectively. Leaching experiments were conducted to evaluate the solubility of nutritive elements K, Ca and Mg in the ash. The results indicated that acid could enhance the solubility compared with pure water. Under the optimal conditions of filtrate final pH neutral, leaching time 20min, ratio of liquid to solid (L/S) 2, reaction temperature 40°C and stirring time 1min just for homogenization, 36.9% of K, 42.8% of Ca and 10.1% of Mg in the ash could be extracted. These dissolution rates were still very low, that means, the thorough extraction is not very easy and further research should be continued to make the straw power industry ecological and sustainable.

Abstract: Huge amount of waste electrical and electronic equipments (WEEE) or electronic waste (E-waste) has been produced every year in the world. It consists of valuable and hazardous metals that can be reused or extracted to minimize the environmental impact. This study is focusing on the investigation of recycling potential of e-waste through manual dismantling process and leaching test. The leaching test was conducted by changing the initial pH with constant stirring speed, constant water-sample ratio and in open air. The morphological structures of the solid samples were observed by SEM and the liquid residue was analyzed by Atomic Absorption Spectroscopy (AAS). It was found that total time required to dismantle all parts in the waste motor is about 10 minutes and the part that required longest dismantling time was armature windings. The metal elements that were observed are Fe, Mg, Pb and Cr. It was found that the pH of the solution increased with the increasing leaching time. The dissolution of Fe and Pb was high in the early stage of leaching but gradually decreased afterward. The dissolution for Mg and Cr was low throughout the leaching process. It was revealed that the metal elements in e-waste can be dissolved using this method and further investigation to increase the dissolution rate is required to ensure that the method proposed is applicable in industry. However, dissolved concentration of Pb must be controlled to ensure that it follows the permissible amount set under environmental standard.

Abstract: The silicone oil leachate in fouling release coatings has very important effect on inhabitting marine organism on ships hull and releasing of biofouling from it. For observing and testifying the leaching phenomenon of silicone oil in PMDS fouling release coating, the coating was designed and prepared consisting of 107 silicone gum, dimethyl silicone oil, tetraethylorthosilicate as crosslinked curing agent, multi-walled carbon nanotube as filler, dibutyltin dilaurate as catalyst. The confocal laser scanning microscopy (CLSM) LEXT OLS4000 was used to observe the morphology of the coating and silicone oil leachate. The results indicate that the dimethyl silicone oil can stably exist and distribute uniformly in PDMS coating. Regardless of between the coating and air or and seawater, silicone oil can leach on the interface. Silicone oil not only can leache faster on the interface between seawater and the coating than that between air and it, but also can easily form the continuous oil film because of the gravity of seawater.

Abstract: In recent years, recovering zinc from zinc calcine with high iron has been a matter of discussion. In this paper, sulfuric acid leaching was carried out to assess the effect of several parameters on zinc and iron extraction in zinc calcine with high iron in which the grade of zinc and iron is 53.90% and 19.38%, respectively. Parameters, such as stirring speed, sulfuric acid concentration, liquid to solid ratio and leaching time, were investigated. The results show that leaching time has done nothing to the leaching rate, but has great influence on leaching efficiency. Liquid to solid ratio and sulfuric acid concentration have significant influence on leaching results, and stirring rate has not obvious influence on leaching results. Under the condition of 120g/L sulfuric acid, 6:1 liquid to solid ratio, 55°C leaching temperature and 120min leaching time, the recovery of zinc and iron is 82.24% and 9.64%, respectively. It is obvious that ZnO in zinc calcine is easy to dissolve in acidity solution, which shown in two aspects: high leaching rate and high leaching speed. ZnO can be dissolved entirely in sufficient sulfuric acid in 10min.

Abstract: Elementary compositions of municipal solid waste incineration (MSWI) fly ash was analyzed. In addition, influence of perchloric acid concentration and liquid to solid ratio on removal efficiency of the four heavy metals was investigated. It was found that there are 11 major elements in fly ash, with content over 1%, and content of them follows sequence of O > Ca > Si > Cl > Al > Fe > Na > S > C > Mg. These major elements account for around 97.5~98.7% of the ash. Removal ratio of Zn, Pb, Cd and Cu followed the decreasing sequence of Zn > Pb > Cd >Cu for acid extraction using perchloric acid. The optimal extraction conditions are: perchloric acid 3 M, liquid to solid ratio 30 mL liquid / 1 g ash, resulting in an extraction ratio of 89% for Zn, 85% for Pb, 41% for Cd and 32% for Cu.