nitrophenols and ferric-hydroxide

This study confirmed the feasibility of natural limonite working as the iron catalyst for the PNP wastewater treatment in the BES-Fenton system. After the start-up period of the BES-Fenton systems, air and limonite powder were injected into the cathode chamber as the original materials for manufacturing Fenton reagents of H₂O₂ and Fe(II) respectively. The experiment parameters like pH, external resistance, limonite dosage and initial PNP concentration were investigated in this research. The removal efficiency of PNP (0.25 mM) could achieve 96% in 6h under the optimal experimental conditions. A limonite dosage of 112 mg per 50 ml of PNP solution at 0.25 mM concentration each time could sustain 7 cycles of the BES-Fenton system operation with PNP removal efficiency >94%. This study suggests an efficiency and cost-effective approach for the PNP removal by using the natural limonite as the iron catalyst of the BES-Fenton system.

Topics: Ferric Compounds; Hydrogen Peroxide; Hydrogen-Ion Concentration; Nitrophenols; Waste Disposal, Fluid; Water Pollutants, Chemical

Electron exchange between aqueous Fe(II) and structural Fe(III) of iron minerals has been illustrated for understanding the reduction of nitroaromatic compounds (NAC). However, factors influencing Fe(II)-induced the reduction of NAC still remain elusive. In this paper, p-nitrophenol (1.5mM) was selected to explore the effects of pH, the stabilizing ligands (Cl(-), SO4(2-)) of ferrous ions and the extra addition of iron hydroxide on the reduction of NAC via Fe(II) species. The results indicate that the reduction degree of is much lower in SO4(2-) medium than that in Cl(-) medium at pH 7.6. p-Nitrophenol reduction increased in SO4(2-) medium and slightly decreased in Cl(-) medium when Fe hydroxide was extra added. Cl(-) strength (0.01-0.1 mol L(-1)) has no obvious effect on p-NP reduction. SO4(2-) species and its dosage have markedly inhibitory effect on p-NP reduction due to the selective adsorption of SO4(2-) and the formation of sulphated surface complexes on the fresh Fe hydroxide.

Topics: Adsorption; Anions; Chlorides; Chromatography, High Pressure Liquid; Electrons; Environmental Restoration and Remediation; Ferric Compounds; Hydrogen-Ion Concentration; Iron; Ligands; Nitrophenols; Oxidation-Reduction; Sulfates; Surface Properties; Wastewater; Water Pollutants, Chemical; X-Ray Diffraction

Ferrous hydroxide colloids were prepared and characterized as an activator of H(2)O(2) for decomposing organic pollutants, such as Rhodamine B, sulfamonomethoxine (SMM) and 4-nitrophenol (4-NP). As major reactive oxygen species, hydroxyl radicals were confirmed to be generated in the activation of H(2)O(2) by using fluorescent probe technique and electron spin resonance technique. The highly-dispersed colloidal nanoparticles with large specific surface area combined the merits of both homogeneous and heterogeneous activator, leading to fast degradation of organic contaminants. Almost complete decolorization of added RhB (0.02 mM), along with a removal of 64.3% of total organic carbon, was achieved within only 1 min by adding 0.30 mM ferrous hydroxide colloids and 1.20 mM H(2)O(2) at pH 7.0. Based on the contributions from the redox activation and the caged activation, a new mechanism was proposed to explain the enhancing effect of the colloids.

Topics: Colloids; Environmental Pollutants; Environmental Restoration and Remediation; Ferric Compounds; Hydrogen Peroxide; Iron; Nitrophenols; Rhodamines; Sulfamonomethoxine