Coagulation behavior and floc characteristics of a novel composite poly-ferric aluminum chloride-polydimethyl diallylammonium chloride coagulant with different OH/(Fe3+ + Al3+) molar ratios

Cuizhen Sun, Jinwei Qiu, Zhibin Zhang, Taha F. Marhaba, Yanhao Zhang

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

In this paper, flocculating performance and mechanisms of a new composite coagulant, poly-ferric aluminum chloride-polydimethyl diallylammonium chloride (PFAC-PD) with different OH-/(Fe3+ + Al3+) molar ratios, were investigated for humic acid (HA)-kaolin synthetic wastewater treatment. The impact of OH-/(Fe3+ + Al3+) molar ratios on the removal efficiencies of turbidity and dissolved organic carbon, specific UV absorbance, coagulation mechanisms and dynamics was explored during the coagulation process using composite coagulants. The coagulation experimental results revealed that the composite coagulants with lower OH-/(Fe3+ + Al3+) molar ratio exhibited better coagulation efficiency. When OH-/(Fe3+ + Al3+) molar ratio of the composite coagulant was 1.5, adsorptionbridging played a dominant role in coagulating HA-kaolin synthetic wastewater. The floc growth rate and floc size, increased with increasing OH-/(Fe3+ + Al3+) molar ratio and the highest peak height of the size distribution was obtained by PFAC-PD with OH-/(Fe3+ + Al3+) =1.5. Also, the composite coagulants with higher OH-/(Fe3+ + Al3+) molar ratio formed more compact flocs, as reflected by the higher fractal dimension value. The flocs coagulated by PFAC-PD with basicity value of 1.0 gave strong strength and good recoverability.

Original languageEnglish (US)
Pages (from-to)1636-1643
Number of pages8
JournalWater Science and Technology
Volume74
Issue number7
DOIs
StatePublished - Oct 2016

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Water Science and Technology

Keywords

  • Basicity
  • Composite coagulant
  • Floc breakage and regrowth
  • Floc strength and recoverability
  • Fractal dimension

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