Optimisation of orthophosphate and turbidity removal using an amphoteric chitosan-based flocculant–ferric chloride coagulant system

Abstract

Environmental contextThe fate and build-up of phosphate nutrients in aquatic environments is an urgent environmental problem affecting global water security. This study, guided by a statistical design method, optimises the flocculation properties of a biopolymer for removing orthophosphate from water. This improved technology has potential widespread applications for removal of orthophosphate from water and wastewater treatment systems. AbstractA coagulation-flocculation process was employed to remove turbidity (Ti) and orthophosphate (Pi) in aqueous media using a ferric chloride (FeCl3) and a grafted carboxymethyl chitosan (CMC) flocculant system. The amphoteric CMC-CTA flocculant was synthesised by grafting 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA) onto the biopolymer backbone of CMC. Here, CMC-CTA denotes the covalent grafting of CTA onto CMC. Optimisation of the variables for Pi and Ti removal was conducted using a jar test system based on the experimental design obtained from the response surface methodology (RSM). The Box–Behnken design was used to evaluate the individual and interactive effects of four independent variables: CMC-CTA dosage, FeCl3 dosage, pH and settling time. The RSM analysis showed that the experimental data followed a quadratic polynomial model with the following optimal conditions: [CMC-CTA]=3.0mgL−1, [FeCl3]=10.0mgL−1, pH 6.8 and settling time=35min. Optimum conditions led to a Pi removal of 96.4% and turbidity removal of 96.7% based on the RSM optimisation, in good agreement with experimental results with an initial concentration of 30.0mg PiL−1. The coagulation-flocculation process is characterised by a combination of electrostatic charge neutralisation, polymer bridging and a polymer adsorption mechanism.

Over dyeing of Lyocell fabric with natural indigo and rhubarb

“…The actual values and predicted values are shown in Table 6, and most actual and predicted values are close, which validates the prediction of this model. 19…”

Utilization of Bioflocculants from Flaxseed Gum and Fenugreek Gum for the Removal of Arsenicals from Water

“…Equation (1)). BBD is a response surface methodology, which is a collection of mathematical and statistical techniques that are useful for the modelling and analysis of systems wherein a response of interest is influenced by several variables, where the goal is to optimize this response [ 27 ]. Preliminary experiments indicate that three important operating parameters in the CF process that affect arsenic removal are the coagulant (FeCl 3 ) dose, flocculant (FSG, FGG or XG) dose and settling time.…”

Kinetics and Thermodynamics of Adsorption for Aromatic Hydrocarbon Model Systems via a Coagulation Process with a Ferric Sulfate–Lime Softening System

“…Many researchers have reported the effectiveness of coagulation for the treatment of effluent with high levels of colloidal particles, organic matter, and suspended solids [ 7 ]. Coagulation is a suitable removal process for colloidal particles (negatively charged) that undergo neutralization by introduction of counter ions (positively charged) in the form of coagulants, which result in particle aggregation [ 8 ]. Chemical coagulants such as aluminum sulfate (alum), poly-aluminum chloride (PAC), alum potash, ferric sulfate or ferric chloride, among other coagulants, have been employed [ 9 ].…”