Hybrid Coagulant Research Articles

Applying hybrid coagulants and polyacrylamide flocculants in the treatment of high-phosphorus hematite flotation wastewater (HHFW): Optimization through response surface methodology

High-phosphorus hematite flotation wastewater (HHFW) is difficult to treat, because it possesses the properties of high concentration suspended solid (SS) and organic pollutant, high alkalinity and strong color. This study was conducted to investigate the treatment of HHFW using coagulation/flocculation process with the mixture of ferric chloride (FC) and polyaluminum chloride (PAC) as coagulants and polyacrylamide (PAM) as flocculants. Results show that a hybrid coagulant (B4), the mixture of FC/PAC in the Fe/Al molar ratio of 3:7, was found to be the most efficient in the coagulation process. PAM flocculants, such as cationic (PAM-C), non-ionic (PAM-N) and anionic (PAM-A), will improve the turbidity removal efficiency. The dosage of the coagulant B4 and the PAM flocculants was optimized using two statistic tools, central composite design (CCD) and response surface methodology (RSM). According to the analysis of variances (ANOVA), three quadratic models with high regression coefficient ( R 2) were obtained. Through RSM optimization, a minimum residual turbidity of 0.8 NTU was achieved when B4 and PAM-N were in the dosage of 356 mg L −1 and 5.4 mg L −1, respectively. The concentration of iron, aluminum and COD in the purified HHFW were 0.055 mg L −1, 0.184 mg L −1 and 33.92 mg L −1, respectively. This study demonstrated that FC/PAC hybrid coagulant, coupling with PAM-N flocculant, has a great potential and economically feasible to the treatment of industrial wastewater containing high turbidity and high alkalinity.

Distribution and transformation of Al species in organic silicate aluminum hybrid coagulants

In this paper, we discuss three novel organic silicate aluminum hybrid coagulants (HC-T, HC-D and HC-A) developed for the first time using tetraethylorthosilicate (TEOS) and two silane coupling agents – diethoxydimethylsilane (DEDMS) and γ-aminopropylmethyldiethoxysilane (APDES) – as Si sources, respectively. The Al–Ferron complexation timed spectrophotometry was used to investigate the distributions of Al species in these hybrid coagulants. Furthermore, the factors that influence the distribution and transformation of Al species were studied. The experiment results show that the type of silane used and the basicity ( B) have significant effects on the distribution of Al species. Al c and Al b are the dominant species in HC-T and HC-A, respectively, because of the different function groups of the silane. The components of Al b in the three hybrid coagulants also vary with the type of silane, and HC-A is inferred to have a homogeneous distribution of Al b species.

Covalently Bound Organic Silicate Aluminum Hybrid Coagulants: Preparation, Characterization, and Coagulation Behavior

Covalently bound organic silicate aluminum hybrid coagulants were synthesized by employing two silane coupling agents [diethoxydimethylsilane (DEDMS), gamma-aminopropylmethyldiethoxysilane (APDES)] as silicon sources. An additional coagulant was synthesized using anothersilane-tetraethylorthosilicate (TEOS) for comparison. Both the coagulant with DEDMS and that with APDES as the silicon source were shown to be covalently bound by infrared (IR) analysis. All three hybrid coagulants were characterized by pH, zeta potential, Al species distribution, and transmission electron microscopy (TEM) analysis. The results indicated that the silicon source played a significant role in aspects of the chemical and physical structure, Al species distribution, and electrochemistry characteristics. Specifically, the coagulant with APDES as the silicon source featured the highest zeta potential value, the highest content of Al13, and reticulated aggregate. The coagulation behaviors of the three hybrid coagulants were also investigated by treating synthetic water containing humic acid (HA). The hybrid coagulant with APDES as the silicon source exhibited the best coagulation behavior in terms of HA removal and turbidity removal, due to the combination of the zeta potential, Al species distribution, and organic functional groups.