Coagulation performance and floc characteristics of polytitanium tetrachloride (PTC) compared with titanium tetrachloride (TiCl4) and iron salts in humic acid–kaolin synthetic water treatment

Abstract

a b s t r a c tPolymeric metal coagulants are increasingly used to improve the coagulation/flocculation process efficiency, yet the research on the development of titanium and particularly polytitanium salts remains very limited. In this study, the performance of recently developed polytitanium tetrachloride (PTC) coagulant was compared with both titanium tetrachloride (TiCl 4 ) and a commonly used coagulant, ferric chloride (FeCl 3 ) in terms of water quality parameters and floc properties. Compared with FeCl 3 coagulant, titanium-based coagulants had broader region of good flocculation in terms of pH and coagulant dose. Further, they achieved higher removal of UV 254 and turbidity but lower dissolved organic carbon (DOC) removal. Charge neutralisation, physical entrapment of colloids within coagulant precipitates and adsorption were found to be the main coagulation mechanisms for TiCl 4 while sweep coagulation and adsorption were found to play a more important role for both FeCl 3 and PTC. The aggregated flocs formed by PTC flocculation had the largest floc size of around 836 lm with the highest floc growth rate. A little distinction of the floc strength factor was found among the coagulants tested (i.e. 44.8%, 44.2% and 38.9% for FeCl 3 , TiCl 4 and PTC respectively) while TiCl 4 coagulant yielded the flocs with the highest floc recovery factor. This study indicates that Ti-based coagulants are effective and promising coagulants for water purification. Besides, the resulted flocculated sludge can be recycled and produce functional TiO 2 photocatalyst which is a significant advantage over conventional coagulants.

Phosphorus Removal Characteristics of Titanium Salts Compared with Aluminum Salt

“…Recently, Ti-based salts have been investigated as an alternavtive coagulant for organic matter (Chekli et al, 2015;Hussain et al, 2014;Shon et al, 2007;Wu et al, 2011;Zhao et al, 2011;Zhao et al, 2014a;Zhao et al, 2014b). However, to the present authors' knowledge, no previous work has reported the efficacy of Ti-based salts on P removal.…”

“…Aluminum (Al)-based salts are the most commonly used chemicals used in wastewater treatment due to their abundant and low cost (Chekli et al, 2015;Hussain et al, 2014). However, use of these salts results in large quantity of sludge; the subsequent treatment of this sludge is costly and environmentally problematic (Chekli et al, 2015;Zhao et al, 2014b). A chemical that produces less sludge than existing methods, or that produces reusable sludge, would reduce the environmental and economic problems associated with sludge handling (Shon et al, 2007).…”

“…Compared to Al-based salts, Ti-based salts produce larger flocs with higher growth rate and consequent faster coagulation rate. The main advantage of Tibased salts is that the flocculated sludge can be recycled by calcination to produce a valuable byproduct: TiO 2 , which has wide applications in paints, cosmetics, solar cells, photocatalysts, and electronic paper (Chekli et al, 2015;Zhao et al, 2014a). Titanium is nontoxic even in large doses, and does not cause adverse effects or toxicity to humans (Chekli et al, 2015;Zhao et al, 2014a).…”

Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water

“…An increasing number of scholars use titanium salt as a coagulant for water treatment. Chekli et al [21] studied the coagulation effect and coagulation mechanism of polymerized titanium salt, and found that it had better treatment effect on algal turbid water. Chang et al[3] prepared a polyaluminum titanium silicate sulfate coagulant by copolymerization and investigated the effects of treatment with turbid water, and the residual turbidity was 0.36 NTU after treatment.In the present study, we present the preparation process of polyaluminum titanium silicate chloride (PATC).…”

“…An increasing number of scholars use titanium salt as a coagulant for water treatment. Chekli et al [21] studied the coagulation effect and coagulation mechanism of polymerized titanium salt, and found that it had better treatment effect on algal turbid water. Chang et al…”