Desorption Kinetics of Legacy Soil Phosphorus: Implications for Non-Point Transport and Plant Uptake

Soil phosphorus (P) solubility and kinetics partly control dissolved P losses to surface water and uptake by plants. While previous studies have focused on batch techniques for measuring soil P desorption kinetics, flow-through techniques are more realistic because they simulate P removal from the system, akin to runoff, leaching, and plant uptake. The objectives were to measure soil P desorption by a flow-through technique at two flow rates and several batch methods, and utilize both for understanding how flow rate impacts the thermodynamics and kinetics of soil P desorption. Desorption obeyed first-order kinetics in two different phases: an initial rapid desorption phase followed by a gradual release. Desorption was limited by equilibrium and the kinetics of physical processes as demonstrated by an interruption test. Dilution-promoted desorption occurred with increasing cumulative volume, which increased desorption rate via first-order kinetics. The batch tests that simulated cumulative solution volume and time of flow-through were similar to the flow-through results; however, the batch methods overestimated the desorption rates due to less limitations to diffusion. Fast flow rates desorbed less P, but at a greater speed than slow flow rates. The differences were due to contact time, cumulative time, and solution volume, which ultimately controlled the potential for chemical reactions to be realized through physical processes. The interaction between these processes will control the quantity and rate of desorption that buffer P in non-point drainage losses and plant uptake.

Mespilus germanica (MG) and Tribulus terrestris (TT) Used as Biosorbents for Lead Removal from Aqueous Solutions: Adsorption Kinetics and Mechanisms

Today, most countries around the globe are facing water resources restrictions, and it is predicted freshwater resources will be more valuable than oil wells in the next century. In the present study, the ability of lead removal using both powders of Mespilus germanica (MG) and Tribulus terrestris (TT) seeds and optimization of the adsorption process have been investigated. Four main parameters were selected for experimental design, namely, pH, time of contact, the ratio of adsorbent to solution volume, and initial concentration of lead in solution, and the optimization of effective parameters on lead adsorption was performed based on central composite design (CCD) under response surface methodology (RSM). According to the statistical results, the proposed model for MG and TT is confirmed with 0.95 and 0.96 correlation coefficient and 0.92 and 0.94 adjusted correlation coefficient, respectively. The results of parameter optimization also showed that both adsorbents have the acceptable ability to adsorb lead from aqueous solutions. Under the optimum conditions with the initial lead concentration of 10 mg/l, MG powder had better performance in lead adsorption of 96.04%, and TT powder also had an acceptive performance of 93.20%. Moreover, the MG and TT adsorbents have the most accordance with the Freundlich and D-R isotherms, respectively.

Structural, Morphological and Optical Properties of Perfume Atomizer Spray Pyrolysis CdO Thin Films: Effect of Solution Volume

CdO films have been deposited on glass substrates with different solution volume (30, 40 and 50 mL) at 200°C using perfume atomizers spray pyrolysis method. X-ray diffraction studies shows that the prepared thin film had cubic and polycrystalline nature. Scanning electron microscope shows the influence of solution volume on surface morphology of the CdO thin film. Optical studies show that in these films the electronic transition is of the direct transition type. The optical energy gap for the films of as deposited are vary from 2.12 to 2.00 eV with solution volume. Photoluminescence results analysis confirmed that the dependence of optical energy gap on solution volume. The Hall measurements were carried out and the results were discussed.

Analyzing changes in a leach solution oxygenation in the process of uranium ore borehole mining

Purpose is to increase uranium content in a PR solution while developing a technique varying oxidation-reduction potential of a leach solution with its oxygenation and identify changes in the oxygenation depending upon sulfuric acid concentration as well as transportation distance of the solution. Methods. A laboratory facility, involving solution tank, pump, Venturi tube, tank to install oxygen analyzer, and a dump tank, has been manufactured under the lab conditions to determine a leach solution oxygenation taking into consideration its delivery rate, sulfuric acid concentration, and temporal preservation of the concentration. Solution flow velocity; the deli-vered solution volume; sulfuric acid concentration; and distance from oxygenation point to a seam changed and varied during the study. Oxygenation was measured with the help of AZ 8403 oximeter; IT-1101 device was used to measure pH value as well as oxidation-reduction potential (ORP). Findings. A technique for a leach solution oxygenation and results of laboratory tests to identify influence of a sulfuric acid as well as transportation distance of a solution on oxygen concentration in the solution have been represented. It has been determined that Venturi tube helps oxygenize a leach solution; in this context, maximum oxygen concentration is achieved if a flow velocity is optimum one. It has been specified that a solution oxygenating depends upon a sulfuric acid concentration decreasing moderately with the increasing distance of the solution transportation. Originality.Following new dependencies have been determined: oxygen concentration in a solution upon a flow velocity and solution volume; and oxygen concentration in a solution upon distance from concentration place and sulfuric acid concentration. Practical implications.A leach solution oxygenation results in the increased oxidation-reduction potential and in the increased content of a useful component in the pregnant solution respectively. The proposed technique is notable for its low capital spending. Moreover, it is integrated easily into the available system being absolutely environmentally friendly.

Use of agro-industrial residues of plantain (Musa paradisiaca) in the adsorption of Ni (II)

The presence of heavy metals in aqueous media represents a severe threat to ecosystems because they are non-biodegradable, toxic, and carcinogenic. In the present work, the utilization of agro-industrial residues from obtaining plantain starch for removing Ni (II) was studied, establishing the effect of temperature, adsorption dose, and initial concentration. The kinetics, equilibrium, and thermodynamic parameters that determine the process were studied. For this purpose, tests were carried out in a batch system maintaining constant stirring (200 rpm), pH (2), and solution volume (100 mL). The remaining metal concentration was determined by atomic adsorption at 237 nm. It was found that the best adsorption conditions were given at 55 ºC, 0.6775 g, and 368 mg/L obtaining a maximum adsorption capacity of 47.57 mg/g corresponding to a removal of 87%. The kinetic model that best fits the experimental data was a pseudo-second-order model, and the isotherm that describes the process is Langmuir and Freundlich, so the adsorption is given by chemisorption and multilayers. The thermodynamic parameters determined suggest that the process is favourable, not spontaneous, endothermic, and irreversible under the studied conditions. The results show that the residual biomass from the obtaining of plantain starch is a good precursor for absorbing Ni (II) in an aqueous solution.

Assessment of Fenvalerate in Water, Soil and Vegetable Samples

Simple and sensitive spectrophotometric scheme was described for the determination of fenvalerate in environmental samples. The scheme was based on the hydrolysis of 1 N of 5 mL NaOH to form cyanohydrin. The cyanohydrin is reacted with bromine and pyridine to form glutaconic aldehyde, which is then coupled with p-Dimethylaminobenzaldehyde to give yellow dye having maximum absorbance at 440 nm. Beer’s law is obeyed over the concentration range of 0.6- 6.2 µg in a nal solution volume of 25 mL. The molar absorptivity of the colored system is 3.84×104 L mol-1cm-1 and Sandell’s sensitivity is 2.4×10-3 µg cm-2. The reproducibility assessed by carrying out seven days replicate analysis of a solution containing 0.6 µg of fenvalerate in a nal solution volume of 25 mL. The standard deviation and relative standard deviation for the absorbance value were found to be ± 3.4×10-3 and 1.5% respectively. The proposed scheme is sensitive and free from the interference of other toxicants. The analytical parameters were optimized and the scheme was applied to the determination of fenvalerate in environmental samples.

Facile Synthesis of Sprayed CNTs Layer-Embedded Stretchable Sensors with Controllable Sensitivity

Flexible electronic devices have gained significant interest due to their different potential applications. Herein, we report highly flexible, stretchable, and sensitive sensors made of sprayed CNT layer, sandwiched between two polymer layers. A facile fabrication process was employed in which the CNT solution was directly sprayed onto a patterned bottom polymer layer, above which a second polymer layer was casted to get a sandwiched composite structure. Varying amounts of CNT solution (i.e., 10, 25, 40, 70, and 100 mL) were sprayed to get conductive CNT layers of different thicknesses/densities. The physical characteristics of the conductive CNT layers were studied through SEM and optical images. The starting electrical resistance values (without strain) as well as the changes in electrical resistance against human body motions were monitored. The synthesized samples exhibited good response against finger and wrist bending. The conductivity of the samples increased with increase of CNT solution volume while the sensitivity followed the inverse relation, suggesting that the sensors with controlled sensitivity could be fabricated for targeted strain ranges using the proposed method.

Phosphate Removal from Wastewater in Batch System Using Waste Mussel Shell

High input of phosphate (PO43–) in rivers can lead to eutrophication, which jeopardizes aquatic life and human health. In this study, PO43– was removed from synthetic solution and domestic wastewater treatment plant effluent (DWTPE) by waste mussel shell (WMS). The PO43– adsorption by WMS was examined for the initial PO43– concentration (7 mg L−1), solution volume (0.2 L), adsorbent dosage (4, 8, 12, 16, and 20 g), and contact time (1-6 d). The batch experiment's optimum performance could reach approximately 75.1% for the removal of PO43– from synthetic solution and approximately 66.2% for the removal of PO43– from DWTPE after a contact time of 5 d. This work suggests that the WMS can remove PO43 from both synthetic solution and DWTPE. Future works are necessary to increase WMS's capacity to adsorb PO43– from waters, either by physical or chemical modification.