Pretreatment by Fenton Oxidation of an Amoxillin Wastewater

Relatively few reported works have dealt with wastewaters arising from amoxillin manufacture. To develop a treatment process for one such wastewater, several physicochemical methods such as coagulation, ultrafiltration, and Fenton oxidation (FO), have been investigated. Among these methods, FO proved effective. Consequently the method was further investigated to identify the appropriate H2O2/FeSO4 ratio, FeSO4 and H2O2 concentrations, and reaction pH and temperature. In relation to the wastewater, a suitable H2O2/FeSO4 weight ratio was 5:1 (molar ratio: 22.4:1) with H2O2 and FeSO4 concentrations at 20?g/L, 4?g/L, respectively. The corresponding pH range was 2.0–4.0 while the reaction temperature was 60°C. Given these conditions, wastewater total organic carbon was reduced by 48.8–49.4%. After FO treatment, reverse osmosis (RO) effectively reduced the dissolved salt content. The contribution of FO and RO pretreatment improved the wastewater’s biodegradability thus making a downstream biotreatment polishing process viable.     

Factorial Design Approach to Investigate the Effects of Groundwater Cooccurring Solutes on Arsenic Removal by Electrocoagulation

Effects of groundwater cooccurring solutes such as phosphate (PO4), silicate (SiO3), bicarbonate (HCO3), calcium (Ca), and iron (Fe) on arsenic removal were investigated in this study. Investigation by two-level full-factorial designed experiments revealed that PO4 and SiO3 have negative effect on arsenic removal, whereas HCO3 has negligible positive effect. The effects of Ca and Fe present in groundwater have positive effect on arsenic removal by electrocoagulation (EC). Hypothesis testing at 5% significance level suggests that alkalinity (HCO3) is not an important parameter in arsenic removal by EC in naturally occurring pH range of water.     

Prediction of Arsenic Removal by Electrocoagulation: Model Development by Factorial Design

Model was developed by two-level five-factor full-factorial designed-experiment to predict arsenic removal from contaminated water by electrocoagulation. Five factors, namely arsenic concentration (As), solution volume (V); current (I), electrode area (A), and current processing time (t) were investigated. Among the factors, arsenic concentration (As) and volume (V) have negative effect, and area (A), time (t), and current (I) have positive effect on arsenic removal. Within the studied levels of the factors, variance analysis at 5% significance level indicated that electrode area is not significant in arsenic removal by electrocoagulation. The model predicted reasonably good arsenic removal (error<2%) from low (0.288 mg/L) and high (0.882 mg/L) initial arsenic concentrations in presence of naturally cooccurring solutes in the groundwater. For the range of operating variables studied, optimum removal of arsenic (98.56%) is obtained at higher arsenic concentration (1.18 mg/L), lower volume (1 L), higher current (3 A), and higher current processing time (120 s).     

糖厂离心机在线动平衡新技术及其振动综合治理的研究和应用

离心机长期运转之后，会出现不平衡和存在较大振动。文中，不但详细地论述了现场离心机组振动的治理与在线平衡这一新技术，而且以实例说明了它的效果。认为这一新技术，具有成本低、工艺简单、高效快捷和试验人员容易掌握等优点，具有推广应用的意义。     

Flexible Operation of Coal Fired Power Plants with Postcombustion Capture of Carbon Dioxide

Carbon capture and storage is one family of technologies that could be used to significantly reduce global carbon dioxide (CO2) emissions. This paper reviews the likely flexibility of power plants with postcombustion capture, with a focus on an improved characterization of the dynamic performance of power plants with CO2 capture. The literature has focused on design and optimization for steady state operation of power plants with capture, often at a single design point. When dynamic behavior is considered, it is possible that designs should be altered for best overall plant performance. Economic trade-offs between improving transport and storage scheme flexibility and constraining power plant operations should also be carefully analyzed, particularly if the captured CO2 is to be used in another process such as enhanced oil recovery. Another important aspect of real plant operation will be adhering to legislative requirements. Further work is required to identify mechanisms that allow flexible operation without undermining any targets set for storing CO2 and/or restricting global CO2 emissions.     

Problems Associated with Removal of Asbestos

Asbestos has been a very useful construction material, and because of this has had widespread use. However, it can be harmful if not handled correctly or removed in a safe manner. The health hazards associated with asbestos exposure have been known since the early 1900s, however, it has only been within the past 10 yrs that serious consideration has been given to the removal of asbestos from buildings. Asbestos removal has been fraught with numerous problems. Some of these include the high cost of removal, changing and nonspecific regulations, various agencies claiming jurisdiction over the substance, lack of information about the seriousness of asbestos‐related diseases, and insurance‐liability considerations. This paper outlines some of the problems associated with asbestos removal and provides recommendations to ameliorate the situation.     

Abatement of CO from relatively simple and complex mixtures: II. Oxidation on Pd-Cu/C catalysts

A low-temperature abatement of carbon monoxide from mixtures as complicated as smoke was considered. Catalytic oxidation and chemisorption of CO on activated carbon-supported Pd and Cu catalysts were investigated. Heterogenized Wacker-type catalysts and the product of catalyst degradation, a dispersed Pd-Cu catalyst, were prepared and found to be promising for the smoke applications. Deactivation of the catalyst was found to be caused by the catalyst dehydration process, which appeared to be reversible. A heat treatment in a CO+O₂ reaction gas flow resulted in the conversion of a Wacker-type transition metal complex catalyst to Pd⁰ atoms or small clusters. This new system composed a very active chemisorbent of CO and a relatively stable oxidation catalyst at elevated temperatures. This immediately prepared catalyst showed 70% removal of CO from smoke. The elements of the mechanisms of CO oxidation were studied under the gas-flow and gas-pulse conditions.     

Adsorption of As(V) from Water Using Nanomagnetite

This paper describes a study of the removal of arsenate [As(V)] from aqueous solutions by adsorption on commercial nanomagnetite (NM). The influences of pH, initial arsenate [As(V)] concentration, and adsorbent concentration were investigated in multiple kinetic runs. The adsorption kinetics and isotherms were investigated in batch experiments. The experimental data were determined to be best described by the pseudosecond-order kinetic model. Langmuir and Freundlich isotherms were used to fit the adsorption data from equilibrium experiments. The findings have revealed that NM has high removal efficiency for arsenate, with its capacity to reduce an initial level of 300 to <5-μg/L As(V), i.e., below the limit (10-μg/L As) set for potable water by the World Health Organization.     

A lumped model for thermal decomposition of urea. Uncertainties analysis and selective non-catalytic reduction of NO

A two-step mechanism for non-catalytic thermal decomposition of urea was investigated. It involves a first order reaction for the thermolysis of urea and a pseudo-first order reaction for hydrolysis of isocyanic acid. Rate constants of these reactions were tuned on experimental measurements of NH₃ and HNCO concentrations at 423-723 K and 1083-1383 K in isothermal flow reactors made of aluminum and ceramic, respectively. A regression analysis by taking the uncertainties in the kinetic parameters into account shown that the resultant pairs of Arrhenius expressions for thermo-hydrolyzing urea were different with a 90% confidence when obtained from the different sets of experimental data. Additional results of ammonia concentration from experiments of urea solution decomposition reported in the literature revealed the reliability of the Arrhenius expressions tuned on the reaction rates obtained in the highest range of temperature in the ceramic reactor. The consistency of these equations was also verified by a comparison between calculated and experimental rates of selective non-catalytic reduction of nitric oxide with urea as reducing agent. A statistical analysis based on the identification of possible tendencies in these residuals again evidences the weakness of the Arrhenius expressions based on the experiments performed at lower temperatures, which was attributed to a non-expected catalytic effect of aluminum reactor walls on reactions rates of urea thermal decomposition.     

Evaluation of Electric Arc Furnace Slag as a Potential Phosphate-Removal Substrate

A study was conducted to evaluate the performance of locally available electric arc furnace slag (EAFS) as a substrate for removing phosphorus from wastewater. First, in a laboratory study, EAFS was found to have high phosphorus removal efficiency for three P concentrations (0.3, 3.0, and 6.0 mg/L); this resulted in nearly 100% phosphorus removal in 24 h. Next, the experiment was repeated using aeration and similar phosphorus removal was observed but in a shorter contact time of 1 h. The adsorption capacity of EAFS was determined to be 1,458 mg/kg. In a pilot-scale study, over 90% P removal took place in the first 4 h under nonaerated conditions, and nearly 100% removal in 8 h. While the P removal with aeration was relatively less initially for the shorter residence times, a 100% removal was observed for the 24-h residence time.