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Adsorption of nitrate from aqueous solution onto modified cassava (Manihot esculenta) straw

Li W., Mo W., Kang C., Zhang M., Meng M., Chen M.

Ecological Chemistry and Engineering. S

2012

Vol. 19, nr 4

629-638

The performance of a new anion exchanger prepared from raw cassava straw (RCS), for the removal of nitrate from aqueous solutions was evaluated in this study. The cassava straw was modified by epichlorohydrin in the presence of pyridine. The influencing factors, adsorption kinetics, and thermodynamics model of nitrate adsorption onto the modified cassava straw (MCS) were studied. The results showed that the zeta potentials of RCS and MCS were -20.5 mV and +37.3 mV, nitrogen contents (N %) of RCS and MCS were 0.43 and 4.96%, respectively. The best nitrate removal results was reached at 0.2 g of adsorbent dosage and pH range of 6.0÷12.0. The modified cassava straw adsorbed nitrate(V) quickly, reaching equilibrium within 30 minutes. The kinetics of nitrate adsorption at different initial concentrations (25, 50 and 75 mg/dm3) all fit a second order reaction. The adsorption rates were controlled by both membrane diffusion and intra-particle diffusion. The adsorption data fit the Freundlich adsorption isotherm and the Langmuir adsorption isotherm. The maximum adsorption capacity was 2.14, 2.00 and 1.81 mmol/dm3 at 293, 303, and 313 K, respectively.

Dokonano oceny wydajności nowego wymieniacza anionowego, wytworzonego ze słomy surowego manioku (RCS), w usuwaniu azotanów z roztworów wodnych. Słomę manioku zmodyfikowano za pomocą epichlorohydryny w obecności pirydyny. Zbadano kinetykę adsorpcji, czynniki wpływające oraz model termodynamiczny adsorpcji azotanów na zmodyfikowanej słomie manioku (MCS). Wyniki pokazały, że potencjały zeta RCS i MCS wynosiły -20,5 mV i +37.3 mV, zawartości azotu (% N) w RCS i MCS wynosiły odpowiednio 0,43 i 4,96%. Najlepsze wyniki usuwania azotanów uzyskano, wykorzystując 0,2 g adsorbentu, w zakresie pH 6,0÷12,0. Zmodyfikowana słoma manioku szybko adsorbowała azotany(V), osiągając stan równowagi po 30 minutach. Kinetyka adsorpcji azotu z roztworów o różnych stężeniach początkowych (25, 50 i 75 mg/dm3) wskazuje na reakcję II rzędu. Szybkość procesu adsorpcji kontrolowała zarówno dyfuzja membranowa, jak i dyfuzja cząsteczkowa. Dane doświadczalne opisano za pomocą modeli izotermy Freundlicha i izotermy Langmuira. Maksymalne pojemności sorpcyjne wynosiły 2,14, 2,00 i 1,81 mmol/dm3 w temperaturach odpowiednio 293, 303 i 313 K.

Fuzzy-based positioning for mobile robots

Shen W., Gu J., Meng M.

Journal of Automation Mobile Robotics and Intelligent Systems

2009

Vol. 3, No. 3

3-12

This paper proposes fuzzy-based positioning algorithms for an iRobot B21r mobile robot, which is equipped with a 180° scanning laser rangefinder and other sensors, in an indoor environment. A novel, dynamic error model for the laser rangefinder is built with consideration of the detection distance and the detection angle. A new concept, the virtual angular point, is introduced in this paper as one of the features for positioning a mobile robot. To position a mobile robot, three kinds of feature points, such as break points, real angular points, and virtual angular points, are employed in this paper. Based on fuzzy evaluation for the accuracy of each feature point, positions obtained by two arbitrary points are fused together by the weighted mean technique, in which weight is determined by the uncertainty represented by fuzzy numbers. Experimental study has been carried out to verify the effectiveness and the accuracy of the algorithms.