Estimation of Soil-Water Characteristic Curve for Cohesive Soils with Methylene Blue Value

This study described a new methylene blue test to measure the methylene blue value (MBV) for 15 cohesive soils and established the relationship between MBV and plasticity index (PI) and between MBV and percent passing No. 200 sieve (P200), respectively. Thereafter, the soil-water characteristic curves (SWCCs) for 15 cohesive soils based on Fredlund and Xing’s model were generated by the pressure plate test. Then, regression equations for determining the four fitting parameters in a previously developed SWCC equation by using the measured MBV were utilized to generate the SWCC for the cohesive soils. At the same time, the slope parameter, bf, in the SWCC equations was found to be associated with the moisture susceptibility of cohesive soils. A higher bf value indicates that the material is more moisture susceptible. In addition, a lower MBV/PI/P200 shows a lower suction at the same degree of saturation; on the other hand, a higher MBV/PI/P200 presents a higher suction. Therefore, the moisture-holding capacity of cohesive soils increases with increasing MBV, PI, and P200. Finally, the proposed estimation method was validated by a comparison between the four determined fitting parameters from MBV and the pressure plate test.

Characterization of char from slow pyrolysis of sewage sludge

The effects of final pyrolysis temperature Tend from 300 ºC to 550 ºC, heating rates β of 2 ºC/min, 3 ºC/min and 5 ºC/min, retention time RT from 45 min to 90 min, and the moisture content MC from 0 to 70% on characteristics of the pyrolysis char from sewage sludge were investigated using a tube furnace in this study. The resulting chars were characterized by sorption of nitrogen (surface area and pore volume). Their adsorption characteristics were evaluated via iodine value and methylene blue value. Either the pore structures or adsorption characteristics depend on the pyrolysis processing and moisture content of the sludge precursors. In terms of iodine value and surface area of the char, Tend of 450 ºC, RT of 75 min and β of 3 ºC/min proved the optimum combination of pyrolysis parameters. The chars have an undeveloped mesopore and macropore structure and a developed micropore structure. The sodium phenoxide adsorption equilibrium data fit well with the Langmuir model of adsorption, suggesting monolayer coverage of sodium phenoxide molecules at the surface of the char. Its adsorption mechanism is mainly physical in nature, enhanced by chemisorption.

Study on Indicators for Granular Activated Carbon Screening and Adsorption Cycle Determining

Four kinds of granular activated carbon GAC were treated by water taken from surface drinking-water sources in Ji’nan. Five adsorption performance indicators of granular activated carbon (GAC) were investigated. The correlation between the indicators and the removal rate of organic matter in raw water was analysed and the results showed that the removal rates of CODMn and DOC were well correlated with iodine value, the coefficient correlations, R2 were 0.8745 and 0.8474 respectively, the removal rates of UV254 was well correlated with methylene blue value (R2 = 0.9454), indicating the capability as indicator for GAC selection. Additionally, one original GAC was used to adsorb organic matter in raw water, as well as the GAC samples treated with four different saturation time in raw water, to investigate the residue rate of adsorption ability. Of all five adsorption performance indicators, it was found that the iodine value, methylene blue value, and tannic acid were negatively related to the residual rate of the GAC absorption ability (R2 was over 0.9). Based on the research, the activated carbon filters in Quehua Water plant in Ji’nan was evaluated and the replacement of them was suggested.

Research on Preparation of Activated Carbon from Thermosetting Epoxy Circuit Board

The activated carbon was prepared by the two-steps carbonization-activation process with printed circuit board (PCB), using KOH, K2CO3, NaOH and Na2CO3 as activators. The influence of temperature, reaction time and the ratio between activator and material on methylene blue value was discussed. Box-behnken design was applied using Design-Expert software to optimize the conditions of preparation according to Response Surface Methodology (RSM).Results showed that activated carbon prepared by chemical activation with KOH or NaOH achieved higher adsorption of methylene blue.