Jianhua Shu

Ultrasound and microwave-assisted preparation of Fe-activated carbon as an effective low-cost adsorbent for dyes wastewater treatment

A composite adsorbent (Fe-activated carbon) was synthesized by impregnating Fe(NO3)3 onto activated carbon, and heated via microwave heating to remove methylene blue (MB), utilizing ultrasound-microwave combined preparation methods. The optimal MB removal capacity and yield of Fe-activated carbon is 257 mg g−1 and 83.31%, respectively, under optimal conditions such as 700 W of microwave power, 700 °C of temperature and 25 min of heating time. The ultrasound was used for assisted-impregnation of Fe(NO3)3 onto the activated carbon via its acoustic cavitation. The removal capacity on MB of Fe-activated carbon increases by 17.12%, as compared to that of it without ultrasound assisted-impregnation. The physico-chemical properties of Fe-activated carbon were examined by XRD, XPS, SEM, EDX, FTIR, Raman and N2 adsorption. Moreover, the existence of Fe3O4 leads to Fe-activated carbon having magnetic properties, which makes it easily separable from dyes wastewater in an external magnetic field. The equilibrium adsorption data showed that the adsorption behavior followed the Langmuir isotherm, and a pseudo-second order model matched well the kinetic data. Compared with raw activated carbon, the maximum monolayer adsorption capacity of Fe-activated carbon increases by 25.96%. According to these results, Fe-activated carbon is a promising adsorbent for the removal of dye from wastewater.

Copper loaded on activated carbon as an efficient adsorbent for removal of methylene blue

Copper loaded activated carbon (Cu-AC) was prepared by impregnating it with cupric nitrate followed by microwave heating and then used for removing dyes in wastewater. The Cu-AC was thoroughly characterized by N2 adsorption and desorption isotherms, SEM, EDS, XRD, XPS, FT-IR, and Raman. It was proven that cupric nitrate was successfully loaded onto activated carbon with the resulting formation of copper, copper oxide, and cuprous oxide. The Cu-AC was used to treat five kinds of dyes in wastewaters (Rhodamine B, MB, Amaranth, Congo red, and Eosin-Y). Comparing the adsorption capacity of these five dye wastewaters, it was proven that copper and copper oxides have photocatalytic degradation ability that can improve dye removal efficiency. Experimental adsorption data of MB were fit using several kinetic and isotherm models. Kinetic studies indicated that a pseudo-second order is the most suitable model for the adsorption process with a correlation coefficient of R2 > 0.999. The equilibrium adsorption data of MB showed that it followed the Langmuir isotherm; the Langmuir maximum adsorption capacity was 373 mg g−1. Compared with ordinary activated carbon, the maximum adsorption capacity of Cu-AC increased by 37.8%. Additionally, through thermodynamic calculations the negative value of ΔG and positive value of ΔH showed that the adsorption was a spontaneous and endothermic process. All the above results reveal that Cu-AC can be an effective absorbent for removing dyes from wastewater.

Comparison of activated carbon and iron/cerium modified activated carbon to remove methylene blue from wastewater

The methylene blue (MB) removal abilities of raw activated carbon and iron/cerium modified raw activated carbon (Fe-Ce-AC) by adsorption were researched and compared. The characteristics of Fe-Ce-AC were examined by N2 adsorption, zeta potential measurement, FTIR, Raman, XRD, XPS, SEM and EDS. After modification, the following phenomena occurred: The BET surface area, average pore diameter and total pore volume decreased; the degree of graphitization also decreased. Moreover, the presence of Fe3O4 led to Fe-Ce-AC having magnetic properties, which makes it easy to separate from dye wastewater in an external magnetic field and subsequently recycle. In addition, the equilibrium isotherms and kinetics of MB adsorption on raw activated carbon and Fe-Ce-AC were systematically examined. The equilibrium adsorption data indicated that the adsorption behavior followed the Langmuir isotherm, and the pseudo-second-order model matched the kinetic data well. Compared with raw activated carbon, the maximum monolayer adsorption capacity of Fe-Ce-AC increased by 27.31%. According to the experimental results, Fe-Ce-AC can be used as an effective adsorbent for the removal of MB from dye wastewater.

Regeneration of spent mercury catalyst for the treatment of dye wastewater by the microwave and ultrasonic spray-assisted method

Abstract Large amounts of spent mercury catalyst (SMC) produced in producing polyvinyl chloride (PVC) has a great influence on the environment. In this work, microwave and ultrasonic spray were applied to regenerate the carrier of SMC. The optimal experimental conditions were the regeneration temperature of 900°C and regeneration time of 60 min. Subsequently, the textures of pores and mercury content, morphology structure and surface functional groups of SMC and the regenerated activated carbon (RAC) were characterized by N2 adsorption and desorption isotherms, ICP, SEM, EDS and FTIR. Additionally, the adsorption behaviors of RAC on methylene orange (MO) and congo red (CR) were explored to study the mechanisms. The results of kinetics and isotherm showed that experimental data were fitted well with the pseudo second-order and Langmuir isotherm model, respectively. The maximum adsorptions of MO and CR were 529 and 301 mg/g at 323 K. The thermodynamic results illustrated that the adsorption MO and CR onto RAC was spontaneous and endothermic. The results demonstrated that RAC prepared from SMC by microwave heating and ultrasonic spray could realize the comprehensive utilization of waste resources.