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A large amount of arsenic-containing wastewater discharged by the non-ferrous metal industry will cause serious environmental problems if it is not properly treated. Pyrolysis char of waste tire is a kind of solid waste. Since the surface properties of tire derived char (TC) are affected by tar/ash adhesion during pyrolysis, it is necessary to modify TC to treat wastewater containing As(V) effectively as an adsorbent. At present, most studies on the modification of TC are prepared into activated carbon by high temperature activation in N2 atmosphere. In this study, TC was modified at room temperature and air atmosphere, and Fe(OH)3-TCNaOH adsorbent with particle size of 61–75 μm was obtained under the premise of the removal rate of As(V) and the settling performance of the adsorbent. When the initial concentration of As(V) was 5 mg/L, the removal rate of As(V) by Fe(OH)3-TCNaOH with a particle size of 61–75 μm could reach 90% within 30 min under a wide pH range (3–9). The adsorption of As(V) by Fe(OH)3-TCNaOH was most affected by the coexistence of PO43-, which resulted in the removal rate of As(V) decreased by about 20%. The adsorption mechanism shows that the significant increase in the number of 3–5 nm mesoporous pores of Fe(OH)3-TCNaOH and the formation of H bonds are beneficial to the adsorption of Fe(OH)3-TCNaOH to As(V), and improve the stability of Fe-As complex. [ABSTRACT FROM AUTHOR]

With the development of industry and agriculture, eutrophication caused by increasing amounts of phosphorus in the environment has attracted people's attention. On the other hand, copper tailings (CT) is a kind of solid waste with large quantity, large area, and easy to cause groundwater and soil pollution. CT is also a potential resource because of its large specific surface area. CT is intended to be used as an adsorbent for removal phosphate in water, but trace heavy metals and a small amount of phosphate in CT may bring negative effects. Calcium hydroxide (Ca(OH)2) was used to modify CT (CCT), hoping to fix the heavy metals and phosphate in CT at the same time. It was found that the removal capacity of CCT was significantly higher than that of CT. The process of phosphate removal by CCT involves electrostatic sorption and surface precipitation, and there is a synergistic effect between CT and Ca(OH)2. The phosphate removal rate of CCT-0.4 increased with the increase of pH value under alkaline conditions. The XRD patterns of phosphate sorption by CCT mean that Ca3(PO4)2, Ca5(PO4)3(OH) and AlPO4 exist in CCT after phosphate removal, indicating that surface precipitation occurs during the removal process. In summary, the removal mechanism of phosphate by CCT is mainly electrostatic attraction and surface precipitation. [ABSTRACT FROM AUTHOR]

In general, ion-exchange adsorption and biological method have higher treatment efficiency for ammonia nitrogen in water, but the existence of salt makes the treatment efficiency of ion-exchange adsorption method decreased due to the competition of salt ions, and the salt also inhibits the activity of microorganisms, which makes the biological method s treatment efficiency decreased. Four transition metals (Co, Ni, Cu and Zn) were used to support montmorillonite, and four transition metal-based montmorillonite were obtained. Compared with montmorillonite, the ammonia-nitrogen removal performance of the four transition metal-based montmorillonite is greatly improved in the range of saline solution pH 9.0 - 11.5. The specific surface area test shows that the transition metal montmorillonite has larger inner space, and its specific surface area is also greatly improved. Moreover, compared with montmorillonite, the modification of transition metals makes the pore size of montmorillonite smaller, which is the exchange between Na+ with smaller ionic radius and transition metal ions with larger ionic radius in the montmorillonite layer. This conclusion is confirmed by energy spectrum analysis, that is, the relative content of Na decreases from 9.46% to 2.75% - 5.48% after the modification of montmorillonite by transition metal. X-ray diffraction analysis also confirmed this point, that is, compared with montmorillonite, NaCl at the characteristic peaks of 31.8°, 45.5°, 56.5° and 75.3°, the intensity of diffraction angles corresponding to the four transition metal-based montmorillonite weakened or even disappeared, indicating that the montmorillonite underwent iso-crystal replacement in the process of metal modification. In the layer, Na+ and other substances were successfully exchanged by Co2+, Ni2+, Cu2+, Zn2+. Scanning electron microscopy shows that the surface structure of montmorillonite is relatively compact, and the surface of transition metal-montmorillonite is porous and uneven, with obvious gullies. These microstructure make metal-montmorillonite have larger specific surface area and more adsorption sites. The four kinds of transition metal-montmorillonite showed a similar trend in the adsorption properties of ammonia nitrogen under the influence of different salt contents, that is, Cu-montmorillonite always maintained the best, which not only had the strongest coordination ability between Cu2+ ion and NH3 molecule, but also had the highest inner hydroxyl group and the largest inner layer spacing. According to the photoelectron spectroscopy analysis, the N1s of Cupric montmorillonite after the removal of ammonia nitrogen indicates that cupric montmorillonite forms a coordination covalent bond with ammonia nitrogen, and there are ion exchange and electrostatic attraction. The adsorption process is more consistent with the quasi-second-order kinetic model. The full spectrum shows that the N element of Cu-montmorillonite increases from 0 to 2.78% before and after removing ammonia nitrogen. [ABSTRACT FROM AUTHOR]