Phosphogypsum Utilization Part Ⅱ: Preparation of Ammonium Sulphate

The aim of this work was to describe the conversion of raw phosphogypsum, issued from the manufacture of H3PO4 by dissolving the phosphate rock in H2SO4, into (NH4)2SO4 and CaCO3.The thermal analysis technique was used to estimate the yield of conversion. (NH4)2CO3 or (NH4)2CO3 with excess NH4OH or (NH4)2CO3 with NH3 gas were used in the preparation of (NH4)2SO4 from phosphogypsum. The obtained samples were separated and tested by chemical and thermogravimetric analyses, infrared spectrum and X-ray diffraction and the optimum conditions of conversion were determined. The results indicated that the yield of conversion equals to 83.37 and 86.70% in case of using (NH4)2CO3 or (NH4)2CO3 with excess ammoniarespectively, while by using NH3 gas the percentage of conversion increased to 94.2% at a flow rate of 6 ml/min. Chemical analysis, infrared spectrum and X-ray diffraction patterns of the yield, (NH4)2SO4 were nearly similar to the standard sample.

Dissolution kinetics of malachite in ammonia/ammonium sulphate solution

The dissolution kinetics of malachite was investigated in ammonia/ammonium sulphate solution. The effects of ammonia and ammonium sulphate concentration, pH, leaching time, reaction temperature, and particle size were determined. The results show that the optimum leaching conditions for malachite ore with a copper extraction more than 96.8% are ammonia/ammonium concentration 3.0 mol/L NHaOH ＋ 1.5 mol/L （NH4）2SO4, liquid-to-solid ratio 25：1 mL/g, leaching time 120 min, stirring speed 500 r/rain, reaction temperature 25 ℃ and particle size finer than 0.045 mm. The dissolution process of malachite with an activation energy of 26.75 k J/tool is controlled by the interface transfer and diffusion across the product layer. A semi-empirical rate equation is obtained to describe the leaching process and the reaction orders with respect to concentration of ammonia and ammonium sulphate are 2.983 0 and 0.941 1, respectively.

Estimation of Acute Toxicity of Ammonium Sulphate to the Fresh Water Catfish,Heteropneustes fossilis——Ⅰ.Analysis of LC_(50) Values Determined by Various Methods

The acute toxic effects of ammonium sulphate to fresh-water catfish, Heteropneustes fossilis (H.fossilis) have been studied by determining LC50 values with 95% confidence limits, by the graphic method, the logistic method, the Spearman and Karber method and the trimmed Spearman-Karber method. The trimmed Spearman-Karber method was found the most ideal for ammonium salt toxicity test. The flaws in the trimmed Spearman-Karber method are also discussed.

Morphological Characterization of γ-Al_2O_3 Membranes Fabricated from Ammonium Aluminum Sulphate

Supported γ-Al2O3 membranes without defects were prepared by the sol-gel procedure. The sol-gel method involved peptization of a boehmite (AlOOH) sol prepared from ammonium aluminium sulphate. The morphology of the supported membranes was characterized by scanning electron microscopy (SEM) and 3D rotational microscopy. Furthermore, the effects of different preparing conditions on morphological characteristics of the membrane were also investigated. The results show that PVA is a good crack-preventing agent and the morphology of supported membranes is affected by many factors, such as Al2O3 and PVA contents of the sol, drying and sintering procedures and intrinsic defects on the substrate surface.

Effect of Biogas Digested Liquid on CH_4 and N_2O Flux in Paddy Ecosystem

Biogas production generates digested slurry as a byproduct. It can be used as a fertilizer especially after its conversion into digested liquid. A pot based study was conducted in order to evaluate the effect of the application of digested liquid on CH4 and N2O flux, and plant biomass in paddy. Analysis revealed that digested liquid treated soils released more CH4 compared to ammonium sulphate and the control. Ammonium sulphate treated soil emitted the highest N20 whereas digested liquid application decreased its emission significantly. Further, the cumulative emission over 101 d of the experiment was found to be higher for CHa （16.9 to 29.9 g m^-2） compared to N20 （-49.3 to 18.9 mg m^-2） for all treatments. Digested liquid application had positive impact on plant variables such as panicle number and weight of panicles. This study suggests that digested liquid application significantly decrease N20 emission and increase CH4 emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH4 emission by following biogas digested liquid could be attributed to the increase in plant biomass.

Effects of Rice Straw Incorporation and Soil Pre－Flooding on the Fate of Applied （^（15）NH_4）_2SO_4－N and Growth of Rice

A pot experiment was conducted to investigate the effects of straw incorporation and soil pre-flooding on the fate of (￣(15)NH_4)_2SO_4-N and the growth of rice. Excessive application of rice straw when incorporated with (￣(15)NH_4)_2SO_4 at the C/N ratio of 40 reduced the loss of (￣(15)NH_4)_2SO_4-N and retarded the growth and development of rice significantly, while no adverse effects were observed on dry weight of panicle and the total recovery of (￣(15)NH_4)_2SO_4-N when rice straw was incorporated with (￣(15)NH_4)_2SO_4 at a C/N ratio less than 25. There were no significant effects of duration of soil pre-flooding within 6 weeks on (￣(15)NH_4)_2SO_4-Nuptake by rice and on rice growth, but, less loss of (￣(15)NH_4)_2SO_4-N was observed in the soil with a longer period of pre-flooding.

Indirect mineral carbonation of titanium-bearing blast furnace slag coupled with recovery of TiO_2 and Al_2O_3

Large quantities of CO2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO2 emission reduction and comprehensive utilization of the solid waste. This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace （TBBF） slag, in which the TBBF slag is roasted with recyclable （NH4）2SO4 （AS） at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH3 produced during the roasting is used to capture CO2 from flue gases. The NH4HCO3 and （NH4）2CO3 thus obtained are used to carbonate the CaSO4-containing leaching residue and MgSO4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium, magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2：1 and 350℃ for 2 h. The leaching solution was subjected to hydrolysis at 102℃ for 4 h with a Ti hydrolysis ratio of 95.7%and the purity of TiO2 in the calcined hydrolysate reached 98 wt%. 99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH3. The carbonation products of Ca and Mg were CaCO3 and （NH4）2Mg（CO3）2·4H2O, respectively. The latter can be decomposed into MgCO3 at 100-200℃ with simultaneous recovery of the NH3 for reuse. In this process, approximately 82.1% of Ca and 84.2% of Mg in the TBBF slag were transformed into stable carbonates and the total CO2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium, cement and light magnesium carbonate production for the replacement of natural resources.

Comparison of Antioxidant Activity and Antioxidant Components in Lettuce, Onion and Tomato Obtained with Different Levels and Forms of Nitrogen Fertilization

The effect of N levels and sources on the antioxidant components in vegetable is not completely understood. Therefore, greenhouse experiments were conducted to determine the changes in antioxidant capacity diphenyl-2-picrylhydrazyl （DPPH） and ferric reducing antioxidant power （FRAP）, total phenolics, ascorbic acid, total carotene and lycopene contents in edible portions of lettuce, onion and tomato due to different nitrogen levels and sources. The experiment included three N levels （20, 40 and 60 kg/ha for lettuce trial and 60, 120 and 180 kg/ha for either onion or tomato） and four nitrogen sources （calcium nitrate, ammonium sulphate, ammonium nitrate and urea）. The antioxidant capacity and phenolic contents in lettuce was enhanced under low nitrogen level, while the antioxidant capacities, phenolics, carotenoids and lycopene in tomato fruits were not significantly affected by the nitrogen dose applied. Application of calcium nitrate caused 50% increase in DPPH and 20% in FRAP of lettuce compared to other nitrogen forms. Tomato treated with calcium nitrate or ammonium sulphate had higher phenolic and ascorbic acid contents than treated plants with ammonium nitrate or urea. Antioxidant tested parameters of onion were not significantly affected by the nitrogen treatments. Nitrogen concentration in tomato fruits significantly correlated with FRAP antioxidant capacity, phenolics, ascorbic acid, carotene and lycopene contents.

Ammonium persulphate promoted synthesis of polyethylene glycol entrapped potassium tribromide and its application in acylation and bromination of some selective organic compounds

In this study, a new method of synthesis of polyethylene glycol supported potassium tribromide （PEG KBr3） and its application in acylation and bromination reactions are reported. Ammonium persulphate oxidizes I（Br to the corresponding tribromide which is entrapped by polyethylene glycol leading to stable PEG KBr3. The reagent is proved to be highly efficient for the acylation of variety of alcohols and bromination of activated aromatic substrates. The method is a mild, one pot reaction and involves no use of toxic reagents.

Morphological characterization of Al_2O_3 membrane fabricated by sol-gel dip-coating method

Alumina membranes without pinholes and cracks were prepared by the sol-gel process using anunordum aluminium sulphate as the starting material. The effects of different preparing conditions on morphology characteristics of the membrane were investigated by scanning electron microscopy and 3D rotational microscopy. The preparing conditions include the amounts of drying control chemical additives （DCCA）, sintering procedure and sol-gel concentration. The results showed that PVA is a good crack-preventing reagent and the morphology of supported membranes was affected by ninny factors, including Al2O3 concentration, PVA/Al2O3 ratio, heating rate, membrane thickness and intrinsic defects of the substrate surface.

Effects of Different Hardeners on the Working Properties and Bonding Strength of Urea-formaldehyde Adhesives

The addition of a hardener is necessary for the curing of urea-formaldehyde (UF) adhesives in the production of MDF and particleboard. The most commonly used hardener, ammonium chloride, however, is suspected to cause the formation of poisonous dioxin when waste boards are combusted and hence considered as a potential source of pollution. To assess the feasibility of substituting ammonium sulphate for ammonium chloride, working properties and bonding strength were measured for UF adhesives with the two ...