Polymeric polyamine: a systematic study on synthesis, characterisation and its application for removal of reactive dye

Reactive dyes are widely used for dyeing especially cotton fabrics in textile industry and are considered to be major contributor of colour and organic load in textile industries wastewater. It is always need of the textile industry to look for cost effective solution for treatment of this coloured effluent. Coagulation-flocculation is most preferred techniques as it is cost effective. A new polyamine polymer was synthesized by poly-condensation of Epichlorohydrin (ECH) and Dimethylamine (DMA). The effects of the process parameters ECH to DMA molar ratio, addition time, reaction temperature on polymerization were systematically studied by measuring viscosity and surface charge of the synthesized polyamine. The process parameters were optimized using response surface methodology (RSM) and Box-Behnken Design (BBD) along with the application of analysis of variance (ANOVA). The viscosity and surface charge were obtained 125 cp (centipoise) and 3501 meq/g respectively for non-cross linked low viscosity polymer (LVP) at optimum condition with ECH to DMA molar ratio 1, addition time 2 h. and at reaction temperature 40 °C. High viscosity polyamine (HVP) with viscosity 3210 cp, surface charge 3320 meq/g and medium viscosity polyamine (MVP) with viscosity 1250 cp, surface charge 3334 meq/g, were synthesized using ammonia (NH₃) as crosslinking agent along with ECH and DMA. Gas chromatography technique was used to identify residual ECH in the product mixture. The chemical and physical properties of all these polymers were studied by Fourier Transform Infrared Spectroscopy (FTIR), charge analyser and viscosity measurements. The flocculation efficiency of all synthesized polymers (LVP, MVP & HVP) was evaluated at different coagulant dose, pH and compared with conventional coagulants i.e. polyaluminium chloride (PAC) and aluminium chlorohydrate (ACH). The flocculation efficiency of these polymers were found to be higher (>95% Remazol Red reactive dye color removal) over a pH range of 3–10 at its optimal dose of 50–60 mg/L whereas optimum dosage required for PAC and ACH were obtained comparatively higher i.e. 400–600 mg/L to achieve 80–93% color removal efficiency. The residual zeta potential of the treated water clearly indicated that flocculation at the optimum conditions resulted charge neutralization and adsorption bridging.