Enhanced coagulation of ferric chloride aided by tannic acid for phosphorus removal from wastewater.
Phosphorus removal from wastewater is of great importance. In the present study, ferric chloride was selected as the coagulant, and tannic acid (TA), a natural polymer, as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus recovery from different types of wastewater. The results showed that TA can accelerate the settling speed by forming flocs with large size, reduce the residual Fe(III) to eliminate the yellow color caused by Fe(III), and slightly increase the phosphorus removal efficiency. The precipitate formed by TA-aided coagulation showed the advantage of releasing phosphorus faster than ferric phosphate, indicating the possibility of phosphorus recovery from wastewater as slow release fertilizer. To further understand the structural characteristics of the precipitate, analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry were employed. The analytical results indicated that TA-Fe-P complex was formed during the coagulation/flocculation processes. Solid phase in the precipitate consisted of TA-Fe-P complex, Fe-TA complex and/or ferric hydroxyphosphate.
Zhou
Yunan
Y
Department of Chemical Engineering, Tsinghua University, Beijing, China.
Xing
Xin-Hui
XH
Liu
Zehua
Z
Cui
Liwen
L
Yu
Anfeng
A
Feng
Quan
Q
Yang
Haijun
H
D002712:Chlorides; D005290:Ferric Compounds / Q000737:chemistry*; D015394:Molecular Structure; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification*; D013634:Tannins / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods; D018508:Water Purification / Q000379:methods*
D002712:Chlorides; D005290:Ferric Compounds; D013634:Tannins; D010758:Phosphorus; C024555:ferric chloride