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The characteristics and hazards of acid coal mine drainage (ACMD) were introduced, and the treatment methods of ACMD were described. Techniques that could be used for source prevention and process containment were analyzed. The widely used terminal treatment technologies at present were summarized, such as the active treatment technology based on neutralization, sulfidation, adsorption and membrane technology, and the passive treatment technology based on chemical, biological and chemical-biological combined method. It was summarized and concluded that the multi-technology combination process was the main trend of engineering application and an effective way for large-scale collaborative treatment of ACMD. Finally, the development prospect of ACMD treatment method was prospected. [ABSTRACT FROM AUTHOR]

Polymerized aluminum magnesium chloride (PAMC) flocculant was prepared from gangue as a raw material, and the effects of pH, the polymerization time, and the polymerization temperature on the performance of the PAMC were investigated by a one-factor test, based on which, orthogonal experiments (three-factor and two-level) were conducted to optimize the relevant parameters. Meanwhile, FTIR and SEM were used to characterize the polymerized aluminum magnesium chloride, and the sample was applied in printing and dyeing wastewater treatment. The results showed that a pH value of 2.2 and a reaction at 60 °C for 4.5 h were the optimal preparation conditions; the characterization analysis showed that the synthesized product was polymerized aluminum magnesium chloride; the turbidity removal rate of the PAMC for printing and dyeing wastewater was increased by 2.1%, the COD removal rate was increased by 3.1%, the ammonia nitrogen removal rate was increased by 2.1%, and the chromaticity removal rate was increased by 9.2% compared with that of PAC. [ABSTRACT FROM AUTHOR]

Coal mine acid drainage is a type of industrial wastewater generated in the process of coal production and utilization that has a low pH and contains a small amount of organic matter and SO42−, which is harmful to the environment. The ·OH scavenger was used to optimize the grounded electrode atomized corona discharge (GEACD) technology for the treatment of coal mine acidic wastewater. The effects of various factors on the discharge effect were investigated, and the optimal operating scheme for the subsequent test was determined as 35 mm distance between barrel electrodes, 0.6 mm diameter of wire electrodes, and a flow rate of 45 mL/min. The effects of discharge voltage, discharge time, and ·OH scavenger on COD removal rate and pH in coal mine acid drainage were also investigated. The results showed that at the optimum discharge voltage of 12 kV, discharge time of 66 min, and SO42− to ethanol concentration ratio of 1, the COD value decreased from 152.84 mg/L to 43.27 mg/L, and the pH value increased from 5.6 to 6.1. [ABSTRACT FROM AUTHOR]

Pharmaceutical residues can cause serious water pollution problems, harm human health and destroy the ecological balance. FeSO4·7H2O optimisation of the earthed atomising corona discharge (Fe-EACD) process was used to dispose of pharmaceutical wastewater in this research. Experiments were analyzed by VI characteristic curves to optimise the electrode distance (20–50 mm) and wire electrode diameter (0.3–0.5 mm). The effects of discharging voltage (7–12 kV), time (0–54 min) and FeSO4 dosage (0.2–1.2 g/L) were investigated using the response surface methodology (RSM). According to the RSM results, the best removal efficiency of COD (89.6%) was detected at the optimal discharging voltage of 12 kV, time of 42 min and Fe2+ concentration of 0.4 g/L. The Fe-EACD process could work efficiently with BOD5/COD ratio moving to 0.49 in an acid environment. The kinetic analysis and mechanism study suggested that the Fe-EACD process was demonstrated well by the pseudo-first-order based on the correlation coefficient (R2). Active •OH producing in the EACD process is responsible for the COD removal and the FeSO4·7H2O as a catalyst can promote the formation of active hydroxyl. In other words, EACD with Fe2+ optimisation was an economic and feasible process for pharmaceutical wastewater treatment. [ABSTRACT FROM AUTHOR]

To design more environmentally friendly, economical, and efficient demulsifiers for oily wastewater treatment, hydrophobic octadecylphosphonic acid (ODPA)-modified Fe3O4 nanoparticles (referred to as Fe3O4@ODPA) were prepared by condensation of hydroxyl groups between ODPA and Fe3O4 nanoparticles using the co-precipitation method. The prepared magnetite nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric/differential thermogravimetric (TG/DTG) analysis. The water contact angles (θW) of Fe3O4@ODPA nanoparticles were more than 120°, indicating hydrophobic nature, and the diameter of the obtained spherical-shaped magnetite nanoparticles was 12–15 nm. The ODPA coating amount (AO) (coating weight per gram Fe3O4) and specific surface area (SO) of Fe3O4@ODPA were 0.124–0.144 g·g−1 and 78.65–91.01 m2·g−1, respectively. To evaluate the demulsification ability, stability, and reusability, the magnetite nanoparticles were used to demulsify an n-hexane-in-water nanoemulsion. The effects of the magnetite nanoparticle dosage (CS), pH value of nanoemulsion, and NaCl or CaCl2 electrolytes on the demulsification efficiency (RO) were investigated. The RO of Fe3O4@ODPA samples was found to be higher than that of bare Fe3O4 samples (S0, ST, and SN) under all CS values. With the increase in CS, the RO of Fe3O4@ODPA samples initially increased and then approached equilibrium value at Cs = 80.0 g·L−1. A maximum RO of ~93% was achieved at CS = 100.0 g·L−1 for the Fe3O4@ODPA sample S2. The pH and two electrolytes had a minor effect on RO. The Fe3O4@ODPA nanoparticles maintained high RO even after being reused for demulsification 11 times. This indicates that the hydrophobic Fe3O4@ODPA samples can be used as an effective magnetite demulsifer for oil-in-water nanoemulsions. [ABSTRACT FROM AUTHOR]

In an attempt to effectively utilize a multitude of surplus sludge from sewage treatment plants, ordinary Portland cement was used to solidify the dry surplus sludge as a building material. The dry surplus sludge and cement were mixed at different proportions with a certain dosage of water and then cured for 3–60 days at room temperature. The unconfined compression strength (RC) of solidified blocks was investigated with respect to the effects of the ratio of liquid to solid (Rl/S), surplus sludge dosage (DS), the dosage of sodium silicate (DNa2SiO3), and the proportion of fly ash (WF). The fabricated solidified blocks were characterized by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray Diffraction Analysis (XRD). The results demonstrated that RC at 60 days reduced obviously with the increase in Rl/s when Ds was given, whereas RC reduced with DS increased to 15.0 wt% from 5.0 wt% for solidified blocks. When DS was 5.0 wt%, RC of 28 days was reduced from 20.87 MPa to 14.50 MPa, with an increase in Rl/s from 0.35 to 0.55. For the given Rl/s, such as Rl/s = 0.35, RC at 60 days was 23.75 MPa, 2.80 MPa, and 2.50 MPa when DS were 5.0 wt%, 10.0 wt%, and 15.0 wt%, respectively, which were relatively lower in comparison to that of Portland cement solidified blocks without surplus sludge (51.40 MPa). In addition, the addition of Na2SiO3 and fly ash was favorable in terms of improving the RC for solidified blocks. RC of 60 days increased initially and then reduced with the increase in DNa2SiO3 from 0.0 wt% to 9.0 wt% at Rl/s = 0.45 and DS = 5.0 wt%. At DNa2SiO3 = 7.5 wt%, Rl/s = 0.45, and DS = 5.0 wt%, the highest RC value of 34.70 MPa was achieved after being cured for 60 days. Furthermore, RC of 60 days increased initially and then reduced with WF increasing from 0.0 wt% to 25.0 wt%, and the highest RC value of 34.35 MPa was achieved at WF = 10.0 wt%, Rl/s = 0.45, and DS = 5.0 wt%. At the ratio of DNa2SiO3 = 7.50 wt%, Rl/S = 0.35, WF = 20 wt%, DS = 15.0 wt% and M = 1.00, RC of 28 days reached 26.70 MPa. With these values, the utilization of sludge utilized (DS = 15.0 wt%) was increased by double compared with DS = 5.0 wt% (20.87 MPa). To investigate the effect of environmental temperature on the mechanical properties and mass of solidified blocks, the freeze-thaw cycling experiment was carried out. The RC of 28 days and the mass of the solidified block reduced with the number of freeze-thaw cycles, increasing for solidified blocks with DS of 5.0 wt%, 10.0 wt%, and 15.0 wt%, manifesting a decrease of 25.60%, 32.30%, and 40.60% for RC and 3.40%, 4.10%, and 4.90% for mass, respectively. This work provides sufficient evidence that surplus sludge has a huge potential application for building materials from the perspective of improving their mechanical properties. It provides an important theoretical basis for the disposal as well as efficient utilization of sludge. [ABSTRACT FROM AUTHOR]