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A novel biochar adsorbent (GP-AMT) is prepared by functionalizing biochar derived from pomelo peel to eliminate Pb (II) from water. GP-AMT was characterized by FTIR, SEM, BET, TGA and XPS. GP-AMT has a large specific area and is multiaperture. The adsorption performance was studied. At the pH = 5, the maximum uptake amount of Pb(II) on GP-AMT reached 420 mg/g. The sorption behavior of GP-AMT obeys with Langmuir and pseudo second-order formula, which shows that the adsorbing property of GP-AMT is uniform chemical sorption. Thermodynamic studies attested that the sorption was an irreversible endothermic course. GP-AMT demonstrated excellent selectivity and reproducibility. After 5 cycles, it still has an excellent sorption property. XPS and zeta potential analysis revealed that the adsorbing nature of GP-AMT for heavy metal ions was coordination and ion exchange. In conclusion, surface modification of biochar can significantly improve its sorption capacity, selectivity and regenerative ability for Pb(II), and reduce the pomelo peel waste pollution.

An outstanding metal-organic framework sorbent (Zn-MOF) was prepared using Zn2+ and 3-amino-5-mercapto-1,2,4-triazole to eliminate toxic metal ions from water. Zn-MOF was detected via using Fourier-transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Zn-MOF is stable and has a very large surface area. The uptake properties of Zn-MOF were investigated. The maximum uptake capacity of Zn-MOF for Pb, Hg, and As ions was 1097, 32, and 718 mg/g, respectively. This was obtained at pH = 4, 5, and 6, respectively. The adsorption data is in good agreement with the Langmuir and pseudo-second-order rate models, indicating that the uptake process of Zn-MOF for toxic metal ions was a single layer uptake on a uniform surface via exchange of valence electrons. Thermodynamics shows that the uptake process is autogenic and endothermic. Zn-MOF can be reused at least 6 times. Mercury and lead strongly coordinated with Zn-MOF. The interaction between arsenic and Zn-MOF is weak chemical coordination and ion exchange. Zn-MOF has wide application prospects for toxic metal ion elimination.

As one of the important strategic materials, chromium has been widely used in metallurgical, refractory, and chemical industry. Ferrochrome is an important additive in the production of alloy steel. According to the carbon content, it is classified as high-carbon ferrochrome (carbon 4–8%), medium-carbon ferrochrome (0.5–4%), low-carbon ferrochrome (0.15–0.50%), micro-carbon ferrochrome (carbon 0.06%), and ultra-micro-carbon ferrochrome (less than 0.03%). But the most widely used one in metallurgical is the first three. This article mainly summarizes the current development of domestic and international medium-low-carbon ferrochrome and summarizes the preparation methods and the influence factors in the smelting process including reduction temperature, reduction time, the reduction agent, and alkalinity.

A novel magnetic Fe-Y binary oxide was prepared by precipitation method and served as an adsorbent to remove arsenic in pollutant. The FTIR, FESEM, XRD and XPS were used to characterize the adsorbent. The adsorption properties of the magnetic Fe-Y binary oxide were tested by batch experiment. The adsorption process complies with the Langmuir model. It indicates that the adsorption process is a single layer adsorption on the surface of the magnetic Fe-Y binary oxide. At the same time, the adsorption process is also very good in accordance with the pseudo second-order kinetic model, indicating that the process is chemiadsorption. When pH = 5, the maximum adsorption capacity was 303 mg/g. The increase of temperature promotes the As(V) adsorption on the magnetic Fe-Y binary oxide. The magnetic Fe-Y binary oxide has high selectivity and regenerative ability at least 5 cycles. The adsorption mechanism of As(V) on the magnetic Fe-Y binary oxide is chelation and ion exchange.

A novel metal organic framework absorbent was synthesized by one step method using 2,2′-dithiodibenzoic acid as organic linker for efficient and selective recovery of Au(III) from aqueous solution. The adsorbent were detected by scanning electron microscope, X-ray diffraction and zeta potential instruments. Its performance was tested by batch experiments. The adsorption isotherm conforms to the Langmuir model, demonstrating that the adsorption process is the uniform monolayer adsorption. The kinetic model is well fitted to the pseudo second-order dynamics model. The maximum adsorption capacity was 1119 mg/g at pH = 2. High temperatures can promote the absorption process. The five adsorption and desorption cycles indicate that the adsorbent has good repeatability for Au(III) adsorption. It could selectively adsorbed Au(III) from wastewater. The adsorption derive from chelation and reduction. The DFT and XPS results show that Au(III) is mainly adsorbed on the adsorbent by coupling with the S atom. These results indicate that it has a high potential to remove Au(III) from industrial wastewater.

Both chromite powder and ferrosilicon have good wave absorbing property in microwave field, the effects of reduction temperature, reduction time, microwave power, raw particle size and material height were investigated. The results from laboratorial experiments have shown that the particle size, microwave power and material layer height have obvious influence on the heating rate of the material. When the particle size is less than 74 μm, the material heating rate increased obviously and the conversion rate of chromium increased. With the particle size is less than 48 μm, chromium conversion rate is highest reaching 72.13%; when the microwave power from 1300 W, the heating rate increased remarkable, the conversion rate of chromium is also increasing and also reduce the heating time and save energy, but the impact on the chromium conversion rate is not obvious; the reduction time and reduction temperature on conversion ratio of chromium effect is very obvious, with the temperature is higher than 1200 °C and the reduction time reduction of chromium is more favorable.

This work focuses on the column absorption and regeneration behavior of a granular red mud (GRM) for absorbing methylene blue (MB) in wastewater. By investigating key parameters, such as packing column height of adsorbent, initial concentration of MB, and flow rate, on the adsorption effects of GRM, the results show that the GRM can effectively remove MB from wastewater. The breakthrough time of the absorption process can be as high as 330 min, when 20.5 cm GRM column was used, with initial concentration and flow rate of MB wastewater being 150 mg L−1 and 4 mL min−1, respectively. The Thomas model is capable of describing the adsorption kinetics. Finally, for assessing the regeneration ability of the loaded GRM, a series of experiments of eluting the MB-loaded column with dilute nitric acid solution, whose pH value is about 3.0, were conducted. The results showed that the regeneration and re-adsorption effect of the GRM column is good.

Preparation of the reduced iron powder has been attempted with mill scale as the iron-bearing material and with wood charcoal as the reducing agent through microwave heating. The response surface methodology (RSM) is used to optimize the process conditions, with wood charcoal, process temperature, and holding time being the three process parameters. The regressed model equation eliminating the insignificant parameters through an analysis of variance (ANOVA) was used to optimize the process conditions. The optimum process parameters for the preparation of reduced iron powders have been identified to be the wood charcoal of 13.8 pct, a process temperature of 1391 K (1118 °C), and a holding time of 43 minutes. The optimum conditions resulted in reduced iron powders with a total iron content of 98.60 pct and a metallization ratio of 98.71 pct. X-ray fluorescence (XRF) was used to estimate the elemental contents of the reduced iron powder, which meets the specification of the HY100.23 first-class iron powder standard. Additionally X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analysis were performed and the results are compiled.

This paper adopts a simple and novel preparation. Taking cellulose as a template, a tubular morphology structure of micro/nano ZnO crystals was obtained by microwave roasting at high temperature. The higher the microwave roasting temperature, the larger the degree of crystallization. The experiments indicate that the best photo catalytic effect can be obtained at 850°C: At this temperature, the oxidation of cellulose is complete. Large quantities of hexagonal shaped ZnO crystal can be observed, specifically the (0001) crystal face. Under ultraviolet-visible irradiation, taking long arc mercury lamp as light source, the material had good photocatalytic activity. The decomposing efficiency of methylene blue reaches 97% in 60min, which is superior to that of preparations without templates at the same temperature.

The ferrous removal process after carbothermic reduction of chromite fines with microwave heating combined with leaching was investigated. Under the following conditions: Reaction temperature: 1150°C , Reaction time : 40min, Semi coke ratio: 12% , the iron content of the reduction product : 13.05% . Metallization achieved was 52.7%. Reduced chromite was leached with 8% of H2SO4 and FeCl3 aqueous solution. The results show that: the recovery rate of chromium can reach 88.06%, the mass ratio of chromium to iron is 3.5:1 for leaching 30 minutes with 8% of H2SO4; the recovery rate of chromium can reach 88.91%, the mass ratio of chromium and iron is 2.56:1 for leaching 4h at room temperature with FeCl3 aqueous solution (100g/L). The leaching time of latter is longer but can realize the circulation effectively and reduce the waste liquid processing problem.1

In the present investigation, the oxidizing roasting process of chromite with sodium carbonate to prepare potassium dichromate crystals was studied in the microwave field with air, by heating the chromite and sodium carbonate. The chromite and sodium carbonate heated separately at 1000 °C in the microwave oven (frequency: 2.45 GHz; power 1.5 kW) in order to study the microwave absorption properties. The dielectric constant and dielectric loss factor of the chromite and sodium carbonate examined. Then, chromite with sodium carbonate taken in (1:2) ratio and heated at 750 °C. Thus obtained samples were characterized using various techniques includes Powder-XRD (XRD), Scanning Electron Microscopy (SEM), and X-ray fluorescence (XRF). The XRD pattern reveals the existence of Fe3O4, Fe2O3, NaAlO2, and Na2CrO4. The iron and aluminum were leached out as Fe2O3 and Al(OH)3 respectively. The resulting sample treated with the KCl to prepare potassium dichromate crystals. Finally, potassium dichromate crystals formed.