Song Cheng

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.

Selective Adsorption of Ag+ on a New Cyanuric-Thiosemicarbazide Chelating Resin with High Capacity from Acid Solutions

A new cyanuric-thiosemicarbazid (TSC-CC) chelating resin was synthesized and employed to selectively adsorb Ag+ from acid solutions. The effects of acid concentration, initial concentration of Ag+, contact time and coexisting ions were investigated. The optimal acid concentration was 0.5 mol/L. The adsorption capacity of Ag+ reached 872.63 mg/g at acid concentration of 0.5 mol/L. The adsorption isotherm was fitted well with the Langmuir isotherm model and the kinetic data preferably followed the pseudo-second order model. The chelating resin showed a good selectivity for the Ag+ adsorption from acid solutions. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy/energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) were used to study the adsorption mechanism. The chelating and ionic interaction was mainly adsorption mechanism. The adsorbent presents a great potential in selective recovery Ag+ from acid solutions due to the advantage of high adsorption capacity and adapting strongly acidic condition. The recyclability indicated that the (TSC-CC) resin had a good stability and can be recycled as a promising agent for removal of Ag+.

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.

Utilization of walnut shell as a feedstock for preparing high surface area activated carbon by microwave induced activation: effect of activation agents

Abstract The present work attempts to convert walnut shell into a high surface area activated carbon by microwave heating and chemical activation. Different activation agents such as KOH, NaOH, K2CO3 and Na2CO3 were utilized to identify a suitable activation agent. The result indicated that KOH was the most suitable activation agent among those agents, with the highest porosity and surface area of activated carbon. The effect of KOH/C mass ratio on the pore structure characteristics of the activated carbon was investigated. An optimal KOH/C mass ratio of 4 was identified, beyond which the surface area as well as the pore volume were found to decrease. The surface area and the pore volume were estimated to be 3276 m2/g and 1.952 ml/g, respectively, meanwhile the microporous proportion was 77.51% under the optimized KOH/C mass ratio. The activated carbon was further characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The findings strongly support that the activation agent has a great effect on the preparation of activated carbon from walnut shell.

Preparation of High Surface Area Activated Carbon from Spent Phenolic Resin by Microwave Heating and KOH Activation

Abstract The spent phenolic resin is as raw material for preparing high surface area activated carbon (HSAAC) by microwave-assisted KOH activation. The effects of microwave power, activation duration and impregnation ratio (IR) on the iodine adsorption capability and yield of HSAAC were investigated. The surface characteristics of HSAAC were characterized by nitrogen adsorption isotherms, FTIR, SEM and TEM. The operating variables were optimized utilizing the response surface methodology (RSM) and were identified to be microwave power of 700 W, activation duration of 15 min and IR of 4, corresponding to a yield of 51.25 % and an iodine number of 2,384 mg/g. The pore structure parameters of the HSAAC, i. e., Brunauer–Emmett–Teller (BET) surface area, total pore volume, and average pore diameter were estimated to be 4,269 m2/g, 2.396 ml/g and 2.25 nm, respectively, under optimum conditions. The findings strongly support the feasibility of microwave-assisted KOH activation for preparation of HSAAC from spent phenolic resin.

Enhanced and selective adsorption of Hg2+ to a trace level using trithiocyanuric acid-functionalized corn bract

A novel trithiocyanuric acid-modified corn bract (TCA-CCB) was prepared, and its removal properties for Hg2+ were investigated. TCA-CCB showed a remarkable absorbability for Hg2+ in mixed ion solutions. Adsorption kinetics experiments indicated that the removal of Hg2+ on TCA-CCB was quick, with a removal rate of 99.07% within 5 min. In addition, the removal rate of Hg2+ exceeded 98% over all pH conditions. The adsorption process can be best described by pseudo-second-order kinetic and Hill isotherm models. The saturated adsorption capacity of TCA-CCB for Hg2+ was 390 mg/g. The TCA-CCB could efficiently adsorb Hg2+ from the simulated wastewater and reduce the Hg2+ concentration from 10 ppm to 12.35 ppb, which was lower than the greatest allowable value of 50 ppb and satisfied the emission standards required by the Chinese government. Moreover, the removal rate of Hg2+ was beyond 99% after three cycles. The results of the zeta potential and X-ray photoelectron spectroscopy (XPS) implied that the chelation and ion exchange between amino/thiol groups and Hg2+ played a significant role in the improvement of the adsorption properties. The corn bract modified by trithiocyanuric acid exhibits apparent advantages in the removal of Hg2+ from ppm to ppb due to its high selectivity, adsorption capacity and stability.

Microwave-Assisted Preparation of Activated Carbon from Eupatorium Adenophorum: Effects of Preparation Parameters

Abstract Eupatorium adenophorum, global exotic weeds, was utilized as feedstock for preparation of activated carbon (AC) via microwave-induced KOH activation. Influences of the three vital process parameters – microwave power, activation time and impregnation ratio (IR) – have been assessed on the adsorption capacity and yield of AC. The process parameters were optimized utilizing the Design Expert software and were identified to be a microwave power of 700 W, an activation time of 15 min and an IR of 4, with the resultant iodine adsorption number and yield being 2,621 mg/g and 28.25 %, respectively. The key parameters that characterize the AC such as the brunauer emmett teller (BET) surface area, total pore volume and average pore diameter were estimated to be 3,918 m2/g, 2,383 ml/g and 2.43 nm, respectively, under the optimized process conditions. The surface characteristics of AC were characterized by Fourier transform infrared spectroscopy, scanning electron microscope and Transmission electron microscope.

Characterization and adsorption properties of La and Fe modified activated carbon for dye wastewater treatment

Abstract An effective adsorbent (Fe-La-AC) was synthesized by impregnating mixed solution ferric nitrate and lanthanum nitrate with activated carbon and heated by microwave to remove methylene blue (MB) from dye wastewater. The Fe-La-AC was characterized by N2 adsorption, Fourier transform infrared spectroscopy, Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy. Moreover, the existence of Fe3O4 leads to Fe-La-AC having magnetic properties, which makes it easily separated and recycled from dye wastewater in an external magnetic field. After modification, the following phenomena occurred: Brunauer-Emmett-Teller surface area, average pore diameter, and total pore volume decreased; graphitization degree decreased. In addition, the equilibrium isotherms and kinetics of MB adsorption on raw activated carbon and Fe-La-AC were examined. The equilibrium adsorption data indicated that the adsorption behavior followed the Langmuir isotherm, and the pseudo-second-order model matched well the kinetic data. The maximum adsorption capacity of Fe-La-AC is 261.10 mg/g, which increases by 26.38% as compared with raw activated carbon. According to these results, Fe-La-AC is a promising adsorbent for the removal of MB from dye wastewater.