FeOOH and nZVI combined with superconducting high gradient magnetic separation for the remediation of high-arsenic metallurgical wastewater

Treatment of sludge hydrothermal carbonization wastewater by ferrous/sodium percarbonate system: Effect of wastewater composition and role of coagulation and oxidation

It is crucial to explore the effect of complex wastewater compositions on the ferrous/sodium percarbonate (Fe(Ⅱ)/SPC) system and the role of oxidation-coagulation in designing water treatment processes. This study employed redundancy analysis to investigate the effects of wastewater constituents on oxidation and coagulation. Raman analysis, X-ray Photoelectron Spectroscopy, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry were used to determine the roles of oxidation and coagulation in the system. The results showed that sulfates and phosphates formed amorphous complexes with iron species via coprecipitation, thereby promoting coagulation to remove organics. Some heavy metals can also be removed by coagulation. The co-activation of SPC by pre-existing transition metals and the added Fe(Ⅱ) facilitated the oxidative removal of organics, while chloride and arsenic were the main inhibitory inorganic substances in the system. Aromatic compounds mainly promoted coagulation, polysaccharides promoted oxidation, humic acid promoted oxidation and coagulation, and C=C/C=O inhibited the Fe(Ⅱ)/SPC system. The oxidation process removed graphitic structures and unsaturated organic matter in the region of (O/C, H/C) = (0.2-0.4, 0.9-2.0) through free radicals and generated amorphous carbon structures and saturated organic matter in the region of (O/C, H/C) = (0.3-0.7, 1.2-1.9). The coagulation process removed aromatic organics with 2-5 rings and unsaturated organics in the region of (O/C, H/C) = (0.2-0.6, 0.7-1.6) with oxygen-containing organics. The combined effects of coagulation and oxidation enhanced the removal efficiency of organic carbon by approximately 40%. This study facilitates the optimization of hydrothermal carbonization wastewater treatment and advanced oxidation processes.

Application of dirty-acid wastewater treatment technology in non-ferrous metal smelting industry: Retrospect and prospect

Dirty-acid wastewater (DW) originating from the non-ferrous metal smelting industry is characterized by a high concentration of H2SO4 and As. During the chemical precipitation treatment, a significant volume of arsenic-containing slag is generated, leading to elevated treatment expenses. The imperative to address DW with methods that are cost-effective, highly efficient, and safe is underscored. This paper conducts a comprehensive analysis of three typical methods to DW treatment, encompassing technical principles, industrial application flow charts, research advancements, arsenic residual treatment, and economic considerations. Notably, the sulfide method emerges as a focal point due to its minimal production of arsenic residue and the associated lowest overall treatment costs. Moreover, in response to increasingly stringent environmental protection policies targeting new pollutants and carbon emissions reduction, the paper explores the evolving trends in DW treatment. These trends encompass rare metal and sulfuric acid recycling, cost-effective H2S production methods, and strategies for reducing, safely disposing of, and harnessing resources from arsenic residue.

Synergistic effect and mechanism of Cd(II) and As(III) adsorption by biochar supported sulfide nanoscale zero-valent iron

Biochar derived from bamboo was used to support sulfide nanoscale zero-valent iron (S-nZVI@BC) for simultaneous removal of Cd(II) and As (III) from aqueous media. Scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) characterization confirmed the successful synthesis of the S-nZVI@BC. Adsorption kinetics and isotherms indicated that co-adsorption of Cd(II) and As(III) onto S-nZVI@BC was well represented by pseudo-second-order model (R²_Cd(II) = 0.990, R²_As(III) = 0.995) and Langmuir model (R²_Cd(II) = 0.954, R²_As(III) = 0.936). The maximum adsorption was 162.365 and 276.133 mg/g for Cd(II) and As(III), respectively, in a co-adsorption system, which was significantly higher than that in a single adsorption system (103.195 and 223.736 mg/g, respectively). Batch experiments showed that the Cd(II)-to-As(III) concentration ratio significantly affected the co-adsorption with the optimal ratio of 1:2. Ca²⁺ and Mg²⁺ significantly inhibited Cd(II) removal. In contrast, phosphate and humic acid significantly inhibited As(III) removal. Electrochemical analysis indicated S-nZVI@BC had a lower corrosion potential and resistance than nZVI@BC, making it more conducive to electron transfer and chemical reaction. Electrostatic adsorption, complexation, co-precipitation, and redox were the primary mechanisms for Cd(II) and As(III) removal. Overall, the present study provides new insights into the synergistic removal of Cd(II) and As(III) by S-nZVI@BC, which is a very promising adsorbent for the effective removal of Cd(II) and As(III) from contaminated wastewater.

FeOOH activating resorcinol-formaldehyde resin nanospheres for the photo-Fenton degradation of organic pollutants

Relative to the traditional homogeneous Fenton process, heterogeneous photo-Fenton system be of superiorities in cost, pH range of application, and environmental compatibility for the degradation of organic pollutants. For the...