Arsenic Speciation by Sequential Extraction from As-Fe Precipitates Formed Under Different Coagulation Conditions

Zhibin Zhang, Jinxiang Li, Cuizhen Sun, Taha F. Marhaba, Wen Zhang, Yanhao Zhang

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The As(V) extraction in the pH-dependent As(V)-Fe(III) precipitates and the corresponding interaction mechanism of As(V) with ferric iron coagulant were systematically investigated in this study. Generally, As(V) removal by coagulation was more susceptible to the influence of the solution pH than that of the coagulant dosage. There was a distinctively bell-shaped pattern for As(V) removal with increasing the solution pHini from 4.6 to 9.4 with varied mass ratios of Fe/As. Specifically, the removal efficiencies of As(V) were enhanced progressively with increasing pH from 4.6 to 6.2. However, As(V) removal declined appreciably as pH further increased to 9.4. The maximum uptake capacities of As(V) by the precipitates were 1.21, 1.10, and 0.95 mg As per mg Fe at pHini 6.2 with the Fe/As mass ratio of 0.6, 0.8, and 1.0, respectively. Approximately 99 % of sorbed amorphous hydrous and crystalline hydrous oxide-bound As(V) were extracted in bearing-As(V) precipitates at relevant pHini values (i.e., 5.0, 7.0, and 9.0), implying that the main mechanism governing As(V) removal process was forming the inner sphere complexes, which can cause much more powerful forces than chemical compounds. Moreover, it has been accounted well with the performances of floc coagulation for As(V) removal evidenced by the characterizations of the floc size distribution, the floc fractal dimension, and the Fourier transform infrared spectroscopy (FT-IR) spectra, respectively. Considering that As extraction can provide insights for understanding As speciation and mobility in settled precipitates, this study will definitely count much in predicting the long-term risks of As-Fe sediments to the natural environment.

Original languageEnglish (US)
Article number309
JournalWater, Air, and Soil Pollution
Volume227
Issue number9
DOIs
StatePublished - Sep 1 2016

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • Ecological Modeling
  • Water Science and Technology
  • Pollution

Keywords

  • Arsenic speciation
  • As(V) removal
  • Coagulation
  • FT-IR spectroscopy
  • Ferric chloride
  • Fractal dimension

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