Effect of acidification and modified Fenton treatment on a contaminated harbour sediment

Abstract

This study presents the results of laboratory experimental oxidation treatments conducted on marine sediments highly polluted with hydrocarbons. The purpose of the study was to compare the effect of a modified Fenton treatment conducted with acidified stabilised H2O2 with one of simple acidification with H2SO4 used as control to evaluate the potential of heavy metal mobilisation. The H2O2 initial concentration was 0.62M and KH2PO4=1.15g center dot L-1. To evaluate changes in the solid and liquid phase, chemical oxygen demand (COD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA) under O2 atmosphere analyses were performed on the solid, while total organic carbon (TOC), COD, pH and Eh were measured on the liquid. Evaluation of the heavy metal mobilisation was performed using sequential extraction procedures. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the carbon and to lower the COD of the sediment. In addition, the treated sediment showed easier-to handle characteristics, reduced caking and lower aggregation capacity. However some mobilisation of Cu occurred while the concentration of Fe lowered

Removal of organotin compounds and metals from Swedish marine sediment using Fenton’s reagent and electrochemical treatment

“…Metals were removed to a somewhat larger extent from the Fenton-treated sediments compared to the electrochemically treated sediments. This is probably due to the low pH (~ 2.0-3.2) in the Fenton process (Gambrell et al, 1991;Zang et al, 2017) causing a metal release in the leachates, but it may also be explained by the degradation of organic matter in the sediments (Kalmykova et al, 2008;Wang and Mulligan, 2009;Mecozzi et al, 2011). Metals (e.g., Cu and Cd) bound to humic acids and other organic acids in sediments through complexation are released if the acids are degraded during the oxidation or protonated due to the low pH.…”

Different fate of Pb and Cu at varied peroxide concentrations during the modified Fenton reaction in soil and its effect on the degradation of 2,4‐dinitrotoluene

“…The observed significant increase in aqueous phase Cu at ≥0.2 mol L −1 H 2 O 2 can be attributed to the destruction of SOM, since such mobilization was not observed at lower H 2 O 2 concentrations, and to the reduction of Cu(II) to Cu(I) by the reductive moieties produced, which promote desorption of Cu from soils, rather than the decrease in the pH of the system at higher H 2 O 2 concentrations . The rate constant for the reduction of Cu(II) by O 2 •‐ in sea water was determined to be (6.63 ± 0.07) × 10 9 M −1 s −1 .…”

“…The rate constant for the reduction of Cu(II) by O 2 •‐ in sea water was determined to be (6.63 ± 0.07) × 10 9 M −1 s −1 . The Cu mobilization can partly be caused by pH changes, but the reactive species produced during reactions play bigger roles . The Cu sorption is more dependent on SOM, while Pb sorption is more dependent on metal oxides, thus, the destruction of SOM could strongly affect the fate of Cu.…”

“…Furthermore, the increased Cu mobilization during Fenton reactions can be supported by the changed Cu distribution in soil constituents shown by the Tessier extraction results in a previous study. The amount of Cu bound to the organic matter fraction and the Fe and Mn oxides (relatively strong binding) decreased, while the Cu in the easily exchangeable fraction and the carbonate fraction (relatively weak binding) increased after Fenton treatment of contaminated sediment …”

About proper membrane process design affected by fouling by means of the analysis of measured threshold flux data

“…Afterwards, on half volume of the overall feedstock a second pretreatment, that is photocatalysis, was adopted. The clarified stream was processed by photocatalysis using home-made composite magnetic nanoparticles coated by titania, irradiated by UV light for 4 h. This pretreatment is very common for the treatment of polluted aqueous streams like wastewater, containing metallic ions and organic matter, and the efficiency of the photocatalyst may be increased if nanometric [35][36][37][38][39][40].…”