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BACKGROUND A novel composite coagulant was prepared from polyferric chloride (PFC) and polydimethyldiallylammonium chloride (PDM) using two different methods: co‐polymerization and composite polymerization. In this investigation, effects of preparation parameters such as PDM/Fe weight ratio (P) and PDM molecular weight on zeta potential and Fe (III) species distribution were also studied. In addition, the effects of those parameters on coagulation efficiency of prepared coagulants in treating drilling wastewater was evaluated and the synthetic coagulants were characterized in terms of typical properties and morphological analysis. RESULTS The improvements in preparation parameters were better charge neutralization capacity and the highest content of active Fe (III) coagulating species due to the presence of cationic polymer. The optimal coagulation efficiency was obtained at a PDM/PFC weight ratio of 0.3 and PDM molecular weight of 200–350 kDa. PFC‐PDM turned out to be a physical mixture according to Fourier transform infrared (FTIR) analysis, although the coagulation behavior was changed after the PFC/PDM composite was formed. Morphology analysis displayed an irregular surface and multi‐branched structure for PFC‐PDM. CONCLUSION The novel composite coagulant PFC‐PDM exhibited a superior flocculation performance and obtained favorable coagulation behavior with more compact flocs and a much better sludge compressibility compared with PFC alone. © 2016 Society of Chemical Industry

The petroleum refinery industry generates a significant amount of wastewater that contains a high level of organic matter, which calls for effective and costly treatments. In this research, the effectiveness of the petroleum refinery effluent (PRE) treatment with physicochemical process of combined adsorption and coagulation was evaluated. The effects of initial pH, hydraulic condition , and combined sequence of treatment process, different treating reagent types and dosages on the chemical oxygen demand (COD) removal were investigated. Additionally, the elimination efficiency of pollutant wastewater was monitored by gas chromatography-mass spectrometry (GC-MS), and Fourier transformed infrared (FT-IR) spectrophotometer was adopted to describe the structure of the wastewater. Wooden activated carbon was chosen as adsorbent at the dosage of 10 g/L as a primary treatment, and 1500 mg/L polymeric magnesium ferric sulfate was used in coagulation. Results showed that adsorption and subsequent coagulation displayed the best performance when initial pH was 9 at shear rates (G) of G1 = 65 s and G2 = 20 s, which reached maximal removal rate of COD and total organic carbon GC-MS testing result revealed that adsorption was effective in phenols and iso-alkanes removal, whereas coagulation was good at removing esters and n-alkanes.