To selectively remove heavy metal from dye solution, inspired by the unique pore structure of ZIF-8, we developed a synthetic strategy for rapid construction of ZnO@ZIF-8 heterostructure photocatalyst for selective reduction of Cr(VI) between Cr(VI) and methylene blue (MB). In particular, ZnO@ZIF-8 core-shell heterostructures were prepared by in situ ZIF-8 crystal growth using ZnO colloidal spheres as template and zinc source within 8-60 min. The shell of the resulting ZnO@ZIF-8 core-shell heterostructure with a uniform thickness of around 30 nm is composed of ZIF-8 crystal polyhedrons. The concentration of organic ligand 2-methylimidazole (Hmim) was found to be crucial for the formation of ZnO@ZIF-8 core-shell heterostructures. Different structures, ZnO@ZIF-8 core-shell spheres and separate ZIF-8 polyhedrons could be formed by altering Hmim concentration, which significantly influences the balance between rate of Zn(2+) release from ZnO and coordinate rate. Importantly, such ZnO@ZIF-8 core-shell heterostructures exhibit size-selective photocatalysis properties due to selective adsorption and permeation effect of ZIF-8 shell. The as-synthesized ZnO@ZIF-8 heterostructures exhibited enhanced selective reduction of Cr(VI) between Cr(VI) and MB, which may find application in the dye industry. This work not only provides a general route for rapid fabrication of such core-shell heterostructures but also illustrates a strategy for selectively enhanced photocatalysis performance by utilizing adsorption and size selectivity of ZIF-8 shell.

Effect of carbonization temperature on adsorption property of ZIF-8 derived nanoporous carbon for water treatment, Microporous and Mesoporous Materials (2016), doi: 10.1016/j.micromeso.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe heat treatment effect on the adsorption capabilities of nanoporous carbon particles derived from Zeolitic Imidazolate Framework-8 (ZIF-8) was investigated at 600, 1000 and 1200 C in this study. The results showed that heat treatment at 1000 C had a significant effect on the adsorption capacity of ZIF-8 (almost 10 times) for the removal of methylene blue (MB) dye from water. Nanoporous carbons were synthesized by direct carbonization of ZIF-8. SEM and TEM images showed that the carbon resulting from ZIF-8 carbonization at various temperatures retained the original structure and morphology of ZIF-8. The carbon nanoparticles carbonized at 1000 C exhibited outstanding adsorption capacities (186.3 mg/g) compared to nanoparticles carbonized at 600 C (49.5 mg/g) and 1200 C (36.7 mg/g) as wellas ZIF-8 (19.5 mg/g) due to the change in surface charge and pore size distribution. The surface functionalities of materials were also characterized by Raman Spectroscopy, N 2 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT2 adsorption-desorption, FTIR and TGA. The surface charge of the carbon particles changed from positive (ZIF-8) to negative as a result of conversion to carbon confirmed by zeta potential of the samples. The ZIF-8 derived carbon nanoparticles were found to be efficient adsorbents for water treatment purposes due to the satisfactory adsorption properties such as high adsorption capacity and good wettability.

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Pulp and paper industry generates large volumes of highly heterogeneous wastewaters containing compounds from wood or other raw material, process chemicals as well as compounds formed during processing. This study has designed a fixed film reactor which uses the concept of biological attached growth treatment to treat the pulp and paper wastewater. The laboratory-scale fixed film reactor is designed with a circular column of 120 cm height, 15 cm inner diameter and a total volume of 23000 cm 3 . The column which constructed in PVC was packed with PVC plastic pipes which were cut into the size of 4.5 cm length and 3 cm diameter and had a specific surface area of 42 cm 2 . An amount of 150 PVC plastic pipes were placed in the digester. The system was found could remove about 53% of BOD 5 and 89% COD. The treatability constant corresponding to the depth of the reactor, k in this study is found to be 0.038 gal/min 0.5 ft and the observed reaction rate constant, K is 0.04 ft/d at 25°C. This fixed-film reactor could be operated as a trickling filter.