Renewable conversion of coal gangue to 13-X molecular sieve for Cd^(2+)-containing wastewater adsorption performance

Using coal gangue(CG)as raw material,a new type of all solid-waste-based 13-X molecular sieve material was controllably prepared by alkali fusion-hydrothermal method.The synthetic molecular sieve was used as a solid adsorbent to treat Cd^(2+)-containing wastewater,and its adsorption behavior on Cd^(2+)in aqueous solution was studied and analyzed.The microstructure and morphology of the molecular sieve were investigated by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM)and specific surface area analyzer.The results show that the synthesized 13-X molecular sieve has higher Brunauer–Emmett–Teller(BET)specific surface area with higher crystallinity and higher adsorption capacity for the heavy metal Cd^(2+).The adsorption process of Cd^(2+)by molecular sieve conforms to the Langmuir isotherm adsorption equation and Lagergren pseudo-second-order rate equation.Combined with thermodynamic calculation,it can be concluded that the adsorption process is physically monolayer,spontaneous and exothermic.In this study,a low-cost and naturally available synthesis method of 13-X molecular sieve is reported.Combined with its adsorption mechanism for Cd^(2+),it provides a feasible and general method for removing heavy metal ions from coal gangue and also provides a new way for the utilization of coal gangue with high added value.

Biosorption and desorption of Cd^(2+) from wastewater by dehydrated shreds of Cladophora fascicularis

The adsorption and desorption of algae Cladophora fascicularis and their relation with initial Cd2+ concentration, initial pH, and co-existing ions were studied. Adsorption equilibrium and biosorption kinetics were established from batch experiments. The adsorption equilibrium was adequately described by the Langmuir isotherm, and biosorption kinetics was in pseudo-second order model. The experiment on co-existing ions showed that the biosorption capacity of biomass decreased with an increasing concentration of competing ions. Desorption experiments indicated that EDTA was efficient desorbent for recovery from Cd2+. With high capacities of metal biosorption and desorption, the biomass of Cladophora fascicularis is promising as a cost-effective biosorbent for the removal of Cd2+ from wastewater.

Interfacial coupling effects in g-C_(3)N_(4)/In_(x)Sb_(2-x)S_(3) heterojunction for enhanced photocatalytic activity under visible light

A series of In_(x)Sb_(2-x)S_(3) nanosheets modified g-C_(3)N_(4)(In_(x)Sb_(2-x)S_(3)-TCN)heterojunctions with different g-C_(3)N_(4) contents were fabricated by an in situ deposition method.All the In_(x)Sb_(2-x)S_(3)-TCN composites were applied as photocatalysts in Cr(Ⅵ)polluted water treatment and the results displayed that In_(x)Sb_(2-x)S_(3)-TCN could effectively remove Cr(Ⅵ)under visible light through synergistic effects of adsorption and photocatalytic reduction.Especially,In_(x)Sb_(2-x)S_(3)-TCN-70(70 mg g-C_(3)N_(4)) exhibited the most excellent adsorption and photocatalytic reduction performance among all composites,which possessed a high equilibrium adsorption capacity of 12.45 mg/g in a 30.0 mg/L Cr(Ⅵ)aqueous solution,and reduced Cr(Ⅵ)to Cr(Ⅲ)within 10 min under visible light irradiation.DRS and PL results indicated that the interfacial coupling effect between g-C_(3)N_(4)and In_(x)Sb_(2-x)S_(3) enhanced the utilization efficiency of visible light and suppressed photoinduced carrier recombination,which improved the photocatalytic activity of composites.Moreover,the photocatalyst exhibited satisfactory reduction activity and good stability after 5 cycles of Cr(Ⅵ)adsorptionphotoreduction.