The aim of the present study was to evaluate the efficiency of sewage sludge application on maize (Zea Mays L.) growth, yield and macroelements accumulation (N, P, K, Ca, Mg) when different doses of sewage were applied accompanied by mineral fertilization. The results indicated that sewage sludge fertilization produces significant increase of maize yield that are evident starting with 200 kg N/ha rate, and the highest increases were recorded in the rate of 400 kg N/ ha. The nitrogen content in the maize leaves increased significantly in the variants fertilized with sludge at a rate over 300 kg N/ha, meanwhile the potassium content of the maize leaves was significantly reduced as a result of sludge fertilization at a rate equivalent to 400 kg N/ha. Nitrogen and phosphorus contents in the maize kernels increased with sewage sludge loading, meanwhile in the case of potassium the data showed that there were no statistically significant changes in the potassium content of the maize kernels under the influence of sewage sludge fertilization. The application of sewage sludge caused a significant increase of the calcium and magnesium contents in the maize leaves at equivalent rates higher than 200 kg/N ha.
The kinetic adsorption of p-cresol from aqueous solution onto mesoporous activated carbon was investigated for 100, 500 and 1000 mg L-1 initial concentrations, at constant 295 K temperature. The kinetic of the adsorption process was discussed using three kinetic models, i.e., pseudo-first order kinetic model, pseudo-second order kinetic model, and Avrami fractionary order kinetic model. In order to provide a mathematically rigorous method for evaluating the kinetic parameters using the original form of the kinetic models, the nonlinear regression was selected as most viable algorithm. The common statistical tools was employed to check the accuracy of fit measure, namely, sum of the squares of the errors SSE, reduced sum of the squares of the errors Red-SSE, coefficient of determination R2, adjusted coefficient of determination Adj R2 and standard deviation SD.
Achieving the process of pyrolysis of biomass in mild conditions is a viable option for optimizing yield in liquid products and reducing coke yield. The partially dried digestate was stabilized by suspending in a reverse emulsion containing the lipid fraction resulting from the processing of the crude digestate, a hydrophobic surfactant of the polyethoxylated castor oil type and a hydrophilic sorbitol-polyethoxylated fatty acid ester type. The pyrolysis of the digestate was carried out in a continuous system, in a quartz tubular reactor, positioned in the central area of a vertical furnace provided with an automatic temperature control system. The experimental program was performed in the presence of two catalysts, Cu and respectively polyphosphoric acid at atmospheric pressure, temperature in the isothermal reaction zone 460 oC and liquid hourly space velocity of 0.33 h-1. The composition of the liquid fractions obtained on the two catalysts differs by the presence of a higher concentration of branched isomers in the case of the polyphosphoric acid catalyst.
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