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Industrial wastewater was seriously polluted, and it was expected to prepare an effective molybdenum removal adsorbent, then investigate its removal effect on molybdenum-containing wastewater, and find the best combination of conditions and the best desorption scheme. One-step hydrolytic oxidation and cross-linking methods were used to prepare Mn3O4 nanoparticles and manganese tetraoxide / chitosan (Mn3O4 / CTS) composite nanoparticles, respectively. Orthogonal methods were used to determine the optimal combinations of Mn3O4/CTS for molybdenum removal. One-way controlled variable method was applied to the desorption test, and the desorption performances under different desorption conditions were analyzed. The results showed that the best conditions for the preparation of Mn3O4 particles were 12 mL of anhydrous ethanol, 110 mL of NaOH, and 40 for 1.5 h, and the molybdenum removal rate was more than 70%. The best molybdenum removal effect was achieved when the Mn3O4/CTS particles were prepared under the conditions of m(chitosan)m(Mn3O4)= 31, 30 mL of acetic acid, 2 mL of glutaraldehyde, and 150 r/min stirring speed, the molybdenum removal rate was 90.62%. The order of the degree of molybdenum removal was as initial pH > adsorbent amount > oscillation speed > temperature. The optimum desorption solu tion was determined to be 0.05 mol/L NaOH, the desorption time was 30 min, the desorption temperature was 40, and the molybdenum removal rate of more than 80% could be satisfied even after 5 times of desorption. The prepared Mn3O4/CTS composite nanoparticles were effective in removing molybdenum and could produce an excellent and stable regeneration effect. [ABSTRACT FROM AUTHOR]

The article focuses on the results of water parameters (COD, pH, electrical conductivity) and the contents of major ions (Ca2+, Mg2+, Na+, K+, , , Cl–, , ) and trace elements (Co, Ni, Cu, Zn, Cd, Pb, Sr, Ba, Mn) for 12 springs in the Bogorodsky and Losino-Petrovsky districts of Moscow oblast. The waters are slightly acidic to near-neutral (pH 5.5–7.5) with the mineralization ranging from 0.07 to 0.5 g/L, the total hardness is 0.63–5.7 mg-eq/L, the water composition is variable. Spring waters are divided into four groups: Cl–SO4–HCO3–(Mg)–Ca, (SO4)–HCO3–Cl–Na–Ca; (Cl)–HCO3–Ca, and mixed. Based on the thermodynamic calculation using the Visual-MINTEQ program, it was found that the predominant dissolved species of Ba, Sr, Mn, Zn, Cd, Ni, and Co in the waters of the surveyed springs are free ions. For Cu and Pb, the factors for the formation of migration species are the predominant anions of water, as well as the presence of organic matter in water. The COD values and nitrogen compound in the waters of individual springs indicate that the formation of the spring water composition is resulted from the infiltration of atmospheric precipitation through the modern sediments subject to anthropogenic loading. The values of other sanitary–chemical indicators (mineralization, pH, total hardness, chlorides, sulfates, magnesium, sodium, manganese), the content of regulated trace elements are lower than their maximum permissible concentrations in drinking water. [ABSTRACT FROM AUTHOR]