Kinetics Of NH4 Research Articles

Synthesis of 4A Zeolite Molecular Sieves by Modifying Fly Ash with Water Treatment Residue to Remove Ammonia Nitrogen from Water

The widespread presence of ammonia nitrogen (NH4+–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH4+–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH4+–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”.

Development of an organomineral fertiliser formulation that improves tomato growth and sustains arbuscular mycorrhizal colonisation

Achieving sustainable agricultural development requires the efficient use of nutrient resources for crop production. Recovering nutrients from animal manures may play a key role in achieving this. Animal manures typically have low nutrient concentrations, and in ratios that are often not ideal for balanced crop nutrition.Here, combinations of organic and inorganic phosphorus (P) were formulated as granular products (organomineral fertilisers) with granule size suitable for transport and spreading. The fertilisers were produced by granulating powdered chicken litter with MAP and urea powders making the following formulations: 0:4, 1:3, 2:2, 3:1, 4:0. The kinetics of NH4+-N and P release from the fertilisers, and the effects on tomato growth and nutrition, as well as arbuscular mycorrhizal formation in roots following fertiliser application, were determined.Cumulative NH4+-N release ceased within 12 h, and was lower in the formulations with higher proportions of chicken litter. The cumulative P released reached approximately 80% of total P in all formulations, and the time to obtain maximum P dissolution was 19 days in the formulation that contained only chicken litter. The organomineral fertilisers increased tomato shoot growth by 15–28% compared to the chicken litter only, MAP only and MAP/urea formulations. Reasonable levels of mycorrhizal colonisation of tomato roots was achieved with the organomineral fertilisers.The results demonstrated that optimum plant growth does not depend solely on immediately available P, and that timing of nutrient supply to match plant demand is important. The combination of chicken litter with MAP sustained nutrient supply and improved plant growth. Taken together, organomineral fertiliser formulations are potential alternatives to inorganic P fertilisers that can improve crop growth and nutrition, while provide a sustainable use for animal production wastes.

Anoxic ammonia removal using granulated nanoscale oxyhydroxides of Fe (GNOF) in a SBR

Microbial mediated anoxic ammonia removal in the presence of granulated nanoscale oxyhydroxides of Fe (GNOF) was investigated in a SBR, as a novel alternative to conventional nitrification and denitrification. Activated sludge flocs collected from a SBR treating sewage was used as seed biomass to develop the process. After confirming the feasibility of anoxic ammonia removal, SBR operations were carried out for 267 days in 9 phases by varying the initial NH4+-N concentrations from 100 to 500 mg/L and cycle time from 2 to 0.5 day. Effective anoxic ammonia removal was achieved in 0.5 day cycle time with the removal rates of NH4+-N and TN as 130 mg/L/d and 115 mg/L/d, respectively. Batch studies showed that the optimum COD/NH4+-N ratio for effective NH4+-N removal was less than or equal to 2. The kinetics of NH4+-N removal, confirmation studies for GNOF coupled nitrification-denitrification and Fe redox cycling involved in the process were also performed and discussed. The developed process is economical as there is no need for aeration and alkalinity.

Maximizing Ammonium Nitrogen Removal from Solution Using Different Zeolites

Zeolite minerals are ideal for removing ammonium nitrogen (NH4(+)-N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch-shaken system or a "tea bag" approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow-through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch-stirred compared to batch-shaken systems, suggesting that diffusion between particles was rate-limiting in the former system. Flow-through cells possessing contact times > 100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4(+)-K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4(+)-K+ exchange followed by a slower one and suggests the 100-s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study.

167 Nutrient Uptake and Growth Performance of OH87 and OH97 Pear Rootstocks

One-year-old (Old Home) OH87 and OH97 pear rootstocks were grown in 2-gallon containers under natural conditions at Corvallis, Ore., in in 1999. Uniform plants were harvested during August and September, and total leaf area, new shoot number and length, and root growth were measured. The kinetics of NH4+ and NO3- uptake by new roots of both rootstocks were determined with the ion-depletion technique. OH87 had larger total leaf area, and more and longer shoots than OH97. Total root biomass was similiar between the two rootstocks, but OH87 had a larger proportion of new roots and more extension roots than OH97. Both rootstocks had lower Km values for NH4+ absorption than for NO3- and therefore both had greater absorptive power for NH4+ than for NO3- at the low nutrient concentrations. The maximum uptake rates (Vmax) of OH97 were similiar for both NH4+ and NO3- absorption, but OH87 had a much higher maximum uptake rate for NO3- than for NH4+.

Thermodynamics of ammonium exchange by clinoptilolite1

An investigation was conducted to study the effect of temperatures from 298 to 328 °K on the kinetics of NH4 + exchange by clinoptilolite using a batch technique, and to elucidate the exchange process using thermodynamic and pseudothermodynamic parameters formulated from experimental data. The rate constants for both adsorption and desorption processes, calculated using the modified Freundlich model, increased with increasing temperature. Changes in rate constants with a 10 °K rise in temperature (Q10) were slightly greater than 1, suggesting a diffusion‐controlled process. Activation energies for adsorption (Em) and desorption (Ed) were 2.32 and 5.65 kJ mol‐1, respectively. The higher Ed value indicated that more energy was needed to desorb NH4 + than to adsorb it. The standard enthalpy change (?H°) for NH4 + exchange was negative, which indicated strong binding of NH4 + on the exchange sites of the zeolite. The change in free energy (AG°) values for NH4 + exchange ranged from 50.58 to 269.27 J mol1 and increased with increasing temperature.

Kinetics of NH4+ Influx in Spruce.

Influxes of 13NH4+ across the root plasmalemma were measured in intact seedlings of Picea glauca (Moench) Voss. Two kinetically distinct uptake systems for NH4+ were identified. In N-deprived plants, a Michaelis-Menten-type high-affinity transport system (HATS) operated in a 2.5 to 350 [mu]M range of external NH4+ concentration ([NH4 +]o). The Vmax of this HATS was 1.9 to 2.4 [mu]mol g-1 h-1, and the Km was 20 to40 [mu]M. At [NH4+]o from 500 [mu]M to 50 mM, a linear low-affinity system (LATS) was apparent. Both HATS and LATS were constitutive. A time-dependence study of NH4+ influx in previously N-deprived seedlings revealed a small transient increase of NH4+ influx after 24 h of exposure to 100 [mu]M [NH4+]o. This was followed by a decline of influx to a steady-state value after 4 d. In seedlings exposed to 100 [mu]M external NO3- concentration for 3 d, the Vmax for NH4+ uptake by HATS was increased approximately 30% compared to that found in N-deprived seedlings, whereas LATS was down-regulated. The present study defines the much higher uptake capacity for NH4+ than for N03- in seedlings of this species.

The kinetics of NH4 + and NO3 − uptake by Douglas fir from single N-solutions and from solutions containing both NH4 + and NO3 −

The kinetics of NH4 + and NO3 − uptake in young Douglas fir trees (Pseudotsuga menziesii [Mirb.] Franco) were studied in solutions, containing either one or both N species. Using solutions containing a single N species, the Vmax of NH4 + uptake was higher than that of NO3 − uptake. The Km of NH4 + uptake and Km of NO3 − uptake differed not significantly. When both NH4 + and NO3 − were present, the Vmax for NH4 + uptake became slightly higher, and the Km for NH4 + uptake remained in the same order. Under these conditions the NO3 − uptake was almost totally inhibited over the whole range of concentrations used (10–1000 μM total N). This inhibition by NH4 + occurred during the first two hours after addition. ei]{gnA C}{fnBorstlap}

Kinetics of NH4+ and K+ uptake by ectomycorrhizal fungi. Effect of NH4+ on K+ uptake

Kinetics of NH4+ and K+ uptake by ectomycorrhizal fungi. Effect of NH4+ on K+ uptake

Effect of Sesbania, Azolla and rice straw incorporation on the kinetics of NH4, K, Fe, Mn, Zn and P in some flooded rice soils

In a greenhouse study, with and without rice plants, of five flooded Philippine rice soils whose organic C (OC) content varied from 0.5 to 3.6%, incorporation ofSesbania rostrata, Azolla microphylla and rice straw affected the kinetics of soil solution NH 4 + −N, K+, Fe2+, Mn2+, Zn2+, and P. Sesbania and Azolla increased NH 4 + −N concentration above the control treatment, whereas rice straw depressed it. In all soils Azolla released less NH 4 + −N than Sesbania. The apparent net N release depended on the soil and ranged from 44–81% for Sesbania and 27–52% for Azolla. These effects persisted throughout the growth of IR36. Soil solution and exchangeable NH 4 + −N increased initially but levelled off between 30 to 80 days and between 20 to 40 days after flooding (DF), respectively. With rice, soil solution NH 4 + −N concentration, reached a peak at 15–40 DF and declined to very low levels (<4mg L−1). In the 3 soils of low OC content nitrogen derived from green manure ranged from 34–53% and the apparent revovery of added green manure N varied from 29–67%. Almost all N released from both Azolla and Sesbania were recovered in the rice plant in all soils except Concepcion with only 77%. The concentration of K+, Fe2+, Mn2+ and P in the soil solution were higher with rice straw than Sesbania and Azolla in all soils except Hanggan which showed no change in Fe2+ and Mn2+ but increased K+ and P. In general, rice straw, Sesbania and Azolla decreased Zn2+ concentration in all soils.