Removal of malachite green in aqueous solution by adsorption on sawdust

Yinghua Song,Sheguang Ding,Shengming Chen,Hui Xu,Ye Mei,Jianmin Ren 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.12

A new adsorbent was synthesized from sawdust, a forest residue, in which methanol was used as a solvent and triethylamine as a modification agent under the following optimum conditions: 25 oC of reaction temperature, 1 : 8.75 of the ratio of sawdust to triethylamine (g :mL) and 1 hour of reaction time. The adsorption capacity of this adsorbent for malachite green was improved by 632.98% in contrast to that of the unmodified sawdust under the same adsorption conditions. Factors affecting the adsorption behavior of this adsorbent for malachite green, such as pH value, adsorption time, temperature and initial dye concentration, were evaluated through experiments in a batch system. The results indicated that the maximum adsorption capacity can be achieved at 5.08 of pH value and adsorption equilibrium can be reached in 6 hours. It was also found that the higher the temperature, the higher the adsorptive capacity would be. The Freundlich isotherm model provides a better description for the adsorption equilibrium when compared with the Langmuir equation in the conditions of the present study. Additionally, to examine the controlling mechanisms of the process, kinetic equations of the mass transfer and chemical reaction, the pseudo-first order model, the pseudo-second order model and the intraparticle diffusion model were used to correlate the experimental data respectively. The adsorption process of malachite green on sawdust tended to be controlled simultaneously by film mass transfer and intra-particle diffusion and it accompanied chemical reactions. It showed that the sawdust modified with triethylamine had good performance for cationic dye and can be used as a biomass adsorbent to treat dyes-containing wastewater with high quality.

Nonlinear model to predict the torsional response of U-shaped thin-walled RC members

Shenggang Chen,Yinghua Ye,Quanquan Guo,Shaohong Cheng,Bo Diao 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.6

Based on Vlasov‟s torsional theory of open thin-walled members and the nonlinear constitutive relations of materials, a nonlinear analysis model to predict response of open thin-walled RC members subjected to pure torsion is proposed in the current study. The variation of the circulatory torsional stiffness and warping torsional stiffness over the entire loading process and the impact of warping shear deformation on the torsion-induced rotation of the member are considered in the formulation. The torque equilibrium differential equation is then solved by Runge-Kutta method. The proposed nonlinear model is then applied to predict the behavior of five U-shaped thin-walled RC members under pure torsion. Four of them were tested in an earlier experimental study by the authors and the testing data of the fifth one were reported in an existing literature. Results show that the analytical predictions based on the proposed model agree well with the experimental data of all five specimens. This clearly shows the validity of the proposed nonlinear model analyzing behavior of U-shaped thin-walled RC members under pure torsion.

Effects of Crack Width on Chloride Penetration and Performance Deterioration of RC Columns with Sustained Eccentric Compressive Load

Papa Niane Faye,Yinghua Ye,Bo Diao 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.2

In a marine environment, the mechanical performance of Reinforced Concrete (RC) structures deteriorates mainly due to the coupling action of service load and/or the corrosion of steel bars. Here, the working conditions of RC columns in a marine environment were simulated in the laboratory. The chloride penetration and performance deterioration of RC columns with different widths for the maximum initial crack of 0, 50, 100 and 200 microns, induced by different levels of external sustained eccentric compressive load and environments of chloride corrosion, were simulated by seawater wet-dry cycles. The results showed that the yielding load and ultimate load of the RC column specimens were significantly decreased as the width of the initial cracks increased. Tensile strain and crack width were both parameters contributing to chloride penetration in the tensile area of the RC column specimens. During the seawater wet-dry cycles, the initial cracks on the column specimens changed. The initial cracks tended to vanish due to the self-healing capacity of concrete when the width of the initial crack was smaller than 50 microns. The initial cracks remained relatively constant when the crack widths were between 50 and 100 microns, and the crack widths increased when the initial crack width was larger than 100 microns.

Impact of seawater corrosion and freeze-thaw cycles on the behavior of eccentrically loaded reinforced concrete columns

Diao, Bo,Sun, Yang,Ye, Yinghua,Cheng, Shaohong Techno-Press 2012 Ocean systems engineering Vol.2 No.2

Reinforced concrete structures in cold coastal regions are subjected to coupled effects of service load, freeze-thaw cycles and seawater corrosion. This would significantly degrade the performance and therefore shorten the service life of these structures. In the current paper, the mechanical properties of concrete material and the structural behaviour of eccentrically loaded reinforced concrete columns under multiple actions of seawater corrosion, freeze-thaw cycles and persistent load have been studied experimentally. Results show that when exposed to alternating actions of seawater corrosion and freeze-thaw cycles, the compressive strength of concrete decreases with the increased number of freeze-thaw cycles. For reinforced concrete column, if it is only subjected to seawater corrosion and freeze-thaw cycles, the load resistance capacity is found to be reduced by 11.5%. If a more practical service condition of reinforced concrete structures in cold coastal regions is simulated, i.e., the environmental factors are coupled with persistent loading, a rapid drop of 15% - 26.9% in the ultimate capacity of the eccentrically loaded reinforced concrete column is identified. Moreover, it is observed that the increase of eccentric load serves to accelerate the deterioration of column structural behavior.

Factors influencing entrepreneurial intentions of Chinese secondary school students: an empirical study

Xiaozhou Xu,Hao Ni,Yinghua Ye 서울대학교 교육연구소 2016 Asia Pacific Education Review Vol.17 No.4

The ideal stage to learn about and foster positive attitudes toward entrepreneurship is believed to be during childhood and adolescence. However, most entrepreneurial studies examine college rather than secondary school students (SSS). Based on a modified theory of planned behavior (TPB), this study used stratified cluster sampling and a questionnaire to review current entrepreneurship education in secondary schools. In addition, the effects of entrepreneurship education, personal traits, and demographics on attitude, subjective norm, perceived behavioral control (PBC), and entrepreneurial intentions (EI) on 1018 SSS in China were studied. Differences, correlations, and structural equation modeling analysis indicated the following. (1) Most SSS had never received entrepreneurship education, likely resulting in lowered entrepreneurial intention and perception of entrepreneurial behavioral performance as unrealistically easy. (2) Cognitive bias existed in SSS’s perceptions of entrepreneurship, and entrepreneurial behaviors were regarded as external cause-oriented activities. (3) Gender and entrepreneurial experience of family member also influenced EI and related variables. (4) Entrepreneurship education and personal traits (locus of control and innovativeness) were significantly positive predictors of EI, and (5) their effects on EI were completely mediated by PBC. The findings supported the TPB predictions, and the results offered some implications for entrepreneurship education in Chinese secondary schools: (1) developing entrepreneurial personal traits while eliminating examination-oriented education, (2) enhancing SSS’s entrepreneurial confidence so entrepreneurial behaviors are perceived as easier and more achievable, and (3) constructing systematic entrepreneurship courses to guarantee transition from secondary to higher education.

Experimental and Analytical Studies of U-Shaped Thin-Walled RC Beams Under Combined Actions of Torsion, Flexure and Shear

Jianchao Xu,Shenggang Chen,Quanquan Guo,Yinghua Ye,Bo Diao,Y. L. Mo 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.3

U-shaped thin-walled concrete bridge beams usually suffer the combined actions of flexure, shear and torsion, but no research about the behavior of U-shaped thin-walled RC beams under combined actions has been reported in literature. Three large specimens of U-shaped thin-walled RC beams were tested under different torque–bending moment ratios (T–M ratios) of 1:5, 1:1 and 1:0 to investigate the mechanical responses such as crack patterns, reinforcement strains, failure modes and ductility. The testing results showed that ductile flexural failures occurred for all three of the U-shaped thin-walled beam specimens, although the combined shear effect of circulatory torque, warping torque and shear force increased as the T–M ratio increased from 1:5 via 1:1 to 1:0, reflected by diagonal cracks and stirrup strains. More specifically, basically symmetrical flexural failure was dominated by the bending moment when the T–M ratio was 1:5; flexural failure of the loaded half of the U-shaped thin-walled section was dominated by the combined action of the bending moment and warping moment, while there were only a few cracks on the other half of the U-shaped section when the T–M ratio was 1:1; and anti-symmetrical flexural failure was dominated by the warping moment when the T–M ratio was 1:0 (pure torsion). A simple method to calculate the ultimate load of such U-shaped thin-walled RC beams under different T–M ratios was suggested, and the calculating results were corresponding well with the experimental results.

Impact response of steel-concrete composite panels: Experiments and FE analyses

Weiyi Zhao,Quanquan Guo,Xuqiang Dou,Yao Zhou,Yinghua Ye 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3

A steel-concrete composite (SC) panel typically consists of two steel faceplates and a plain concrete core. This paper investigated the impact response of SC panels through drop hammer tests and numerical simulations. The influence of the drop height, faceplate thickness, and axial compressive preload was studied. Experimental results showed that the deformation of SC panels under impact consists of local indentation and overall bending. The resistance of the panel significantly decreased after the local failure occurred. A three-dimensional finite element model was established to simulate the response of SC panels under low-velocity impact, in which the axial preload could be considered reasonably. The predicted displacements and impact force were in good agreement with the experimental results. Based on the validated model, a parametric study was conducted to further discuss the effect of the axial compressive preload.