Reply to the comments on "Facilely synthesized cobalt doped hydroxyapatite as hydroxyl promoted peroxymonosulfate activator for degradation of Rhodamine B" by Zuo et al.

In a Co-HAP/PMS system, catalytic degradation process of RhB was accompanied by the gradual leaching of cobalt ion. The results of additional experiments showed that leached cobalt ion indeed contributed to active PMS for RhB degradation, which was not addressed in the previous study. The finding of the contribution from leached cobalt ion to PMS activation was reported due to the valuable comments of Zuo et al., what will be concerned in the future work. Importantly, Co-HAP still showed a significant contribution to PMS activation for RhB degradation at the initial stage. Fortunately, the release of Co2+ from Co-HAP was slow, the secondary pollution could not be addressed due to the slightly release of Co2+ ion that the Co2+ concentration is lower than the standard of the discharge wastewater. Furthermore, the mechanism of non-radical reaction in the Co-HAP/PMS system was reported to confirm the heterogeneous catalysis of a Co-HAP/PMS system.

Highly-efficient and easy separation of hexahedral sodium dodecyl sulfonate/δ-FeOOH colloidal particles for enhanced removal of aqueous thallium and uranium ions: Synergistic effect and mechanism study.

Thallium (Tl) and uranium (U) contaminants pose serious threats to the ecological environment and human health. In this research, a cost-effective feroxyhite (δ-FeOOH) dispersed with sodium dodecyl sulfonate (SDS) was prepared and a series of experiments were optimized to explore the removal mechanism of Tl+ and UO22+ from the effluent. The SDS/δ-FeOOH exhibited highly dispersed colloidal particles and showed significantly enhanced adsorption performance on the removal of Tl and U in the presence of H2O2 and pH of 7.0. Equilibrium uptakes of 99.5% and 99.7% were rapidly achieved for Tl+ and UO22+ within 10 min, respectively. The Freundlich isotherm model fitted well with the adsorption data of Tl and U. The maximum isotherm sorption capacity of SDS/δ-FeOOH for Tl+ and UO22+ was 182.9 and 359.6 mg/g, respectively. The sorption of Tl followed the pseudo-second-order kinetic model, whereas the sorption of U followed the pseudo-first-order kinetic model. The uptake of Tl and U by SDS/δ-FeOOH was notably inhibited at Na+, K+ concentrations over 5.0 mM, and a high content of dissolved organic matter (over 0.5 mg/L). The mechanistic study revealed that ion exchange, precipitation, and surface complexation were main mechanisms for the removal of Tl and U. The findings of this study indicate that stabilizer dispersion may serve as an effective strategy to facilitate the treatment of wastewater containing Tl and U by using δ-FeOOH.

Removal of U(VI) from aqueous and polluted water solutions using magnetic Arachis hypogaea leaves powder impregnated into chitosan macromolecule.

In this study m-AHLPICS (magnetic Arachis hypogaea leaves powder impregnated into chitosan) was prepared and utilized as an adsorbent to remove U(VI) from aqueous and real polluted wastewater samples. m-AHLPICS was characterized by using the BET, XRD, FTIR, SEM with elemental mapping and magnetization measurements. Different experimental effects such as pH, dose, contact time, and temperature were considered broadly. Chitosan modified magnetic leaf powder (m-AHLPICS) exhibits an excellent adsorption capacity (232.4 ± 5.59 mg/g) towards U(VI) ions at pH 5. Different kinetic models such as pseudo-first-order, and pseudo-second-order models were used to know the kinetic data. Langmuir, Freundlich and D-R isotherms were implemented to know the adsorption behavior. Isothermal information fitted well with Langmuir isotherm. Kinetic data followed by the pseudo-second-order kinetics (with high R2 values, i.e., 0.9954, 0.9985 and 0.9971) and the thermodynamic data demonstrate that U(VI) removal using m-AHLPICS was feasible, and endothermic in nature.

Impregnation of magnetic - Momordica charantia leaf powder into chitosan for the removal of U(VI) from aqueous and polluted wastewater.

Uranium (U(VI)) is radioactive and the primary raw material in the production of nuclear energy. Hence the research associated with uranium removal gained a lot of importance because to reduce the threat of uranium contamination to ecology and its environment surroundings. Thus, economically as well as environmentally friendly sorbents with a good sorption capacity have to be acquired for the removal of U(VI) pollutants from the aqueous and polluted sea samples. In this study magnetic- Momordica charantia leaf powder impregnated into chitosan (m-MCLPICS) was prepared through the impregnation method. After preparation the adsorbent undergone through various characterizations such as BET, XRD, FTIR, SEM with elemental mapping, and VSM analysis. The specific surface area (93.12 m2/g), pore size (0.212 cm3/g) and pore volume (15.35 nm) of m-MCLPICS was obtained from the BET analysis. A pH value of 5 and 0.5 g of adsorbent dose were selected as an optimum values for U(VI) removal. Kinetic data follows the pseudo-second-order model, and the equilibrium data fitted well with the Langmuir isotherm model. ΔG° (-1.6999, -2.4994, -3.5476 and -4.5147 kJ/mol), ΔH0 (25.1 kJ/mol) and ΔS0 (0.089 kJ/mol K) indicates that the U(VI) sorption process is feasible, spontaneous and endothermic.

Facilely synthesized cobalt doped hydroxyapatite as hydroxyl promoted peroxymonosulfate activator for degradation of Rhodamine B.

Hydroxyapatite (HAP) is a promising supporter of catalyst due to its potential in immobilizing metals stably. HAP supported cobalt-based catalyst (Co-HAP) was synthesized via a facile ion exchange-calcination method to reduce the Co leaching. The synthesized Co-HAP was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET) analysis and X-ray photoelectron spectroscopy (XPS). Cobalt ions were incorporated into HAP structure and Co3O4 on HAP surface. Co-HAP showed satisfactory performance in peroxymonosulfate (PMS) activation for eliminating Rhodamine B (RhB) in aqueous solution. Co-HAP even revealed a better activity than that of CoFe2O4. •OH, SO4•- and 1O2 were all involved in RhB degradation and 1O2 played a leading role. High content of surface oxygen groups could be found on Co-HAP after RhB degradation, which might be resulted from the high amounts of hydroxyl groups. The presence of hydroxyl groups performed the co-catalytic activity of PMS activation in Co-HAP/PMS system.

Modification of chitosan macromolecule and its mechanism for the removal of Pb(II) ions from aqueous environment.

It is well-known that heavy metals are non-biodegradable and have been showing remarkable impacts on the environment, public health and economics. Because of high toxic tendency, lead (Pb), is one of the foremost considerable hazardous metal with high environmental impacts. Chitosan is a polysaccharide, and can be utilized in wastewater treatment because of its good sorption ability. Amino and hydroxyl groups (C-3 position) on chitosan can serve as electrostatic interaction and complexation sites for metal cations. Chemical crosslinking can effectively enhance the stability of chitosan in acidic media. Hence a novel, cost-effective and eco-friendly ZnO incorporated into aminated chitosan Schiff's base (ACSSB@ZnO) has been synthesized, characterized (BET, XRD, FTIR, SEM, TEM and 1H NMR), and utilized as an adsorbent for the removal of Pb(II) ions from the aqueous environment. The various operating parameters, such as pH (2-8), agitation speed (30-180), adsorbent dose (0.1-0.8 g), contact time (0-140 min), metal ion concentration and temperature (303-323 K) were investigated. The maximum sorption capacity of Pb(II) onto ACSSB@ZnO was found to be 55.55 mg/g. The equilibrium, and kinetic studies suggested that the adsorption process followed the Langmuir isotherm and Pseudo-Second-Order model. Thermodynamic data showed that the sorption process was feasible, spontaneous, and endothermic.

Ultrasound assisted zero valent iron corrosion for peroxymonosulfate activation for Rhodamine-B degradation.

In this work, ultrasound (US) irradiation assisted powder zero valent iron (ZVI) corrosion was conducted for peroxymonosulfate (PMS) activation. PMS activation activity was evaluated by Rhodamine-B (Rh B) degradation efficiency. The other US/PMS, ZVI/PMS, Fe2+/PMS and US/PMS/Fe2+ systems were performed to investigate the synergistic effects of US and ZVI on PMS activation activity. US/PMS/ZVI system performed the highest activity of Rh B degradation. 99.76% of Rh B was removed within 12 min under the optimum condition (pH = 4.5, ZVI dosage = 1 g/L, PMS = 1 mM, US power = 50 W). A comparison of US/PMS/ZVI system with PMS/ZVI and homogeneous US/PMS/Fe2+ systems for Rh B degradation was conducted, indicating that ultrasound irradiation contributed to acceleration of ZVI corrosion and removal of passive films. Besides, the electrons transformation from Fe0 to PMS made main contribution to the generation of sulfate radical, which resulted in the ability of degradation of Rh B. ZVI could be reused for five cycles with efficient activity of PMS activation. Exhaustion of ZVI led to the decrease in PMS activation at the sixth recycle. Thus, this work presents important information on understanding reuse of iron fillings for PMS/PS activation in practical application of pollution remediation.