Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

Abstract

The co-occurrence of arsenic (As) and organic ligands in water bodies has raised environmental concerns due to their toxicity and adverse effects on human health. The present study aims to elucidate the influences of hydrophobic/hydrophilic organic ligands, such as humic acid (HA) and salicylic acid (SA), on the interactive behavior of As species in water. Moreover, the competitive removal behaviors of As(III, V) species and total organic carbon (TOC) were systematically investigated by coagulation-flocculation-sedimentation (C/F/S) under various aqueous matrices. The results showed the stronger binding affinity of As(V) than As(III) species, with a higher complexation ability of hydrophobic ligands than hydrophilic. The media containing hydrophilic ligands require smaller ferric chloride (FC) doses to achieve the higher As(III, V) removal, while the optimum FC dose required for As(III) removal was found to be higher than that for As(V). Moreover, hydrophobic ligands showed higher TOC removal than hydrophilic ligands. The pronounced adverse effect of a higher concentration of hydrophobic ligands on the removal efficiencies of As(V) and TOC was observed. The adsorption of As(V) on Fe precipitates was better fitted with the Langmuir model but the Freundlich isotherm was more suitable for As(III) in the presence of hydrophilic SA. Moreover, TOC removal was substantially decreased in the As(V) system as compared to the As(III) system due to the dissolution of Fe precipitates at higher As(V) concentrations. The results of FC composite flocs demonstrated that the combined effect of oxidation, charge neutralization and adsorption played an important role in the removal of both toxicants during the C/F/S process. In summary, the findings of the present study provide insights into the fate, mobility and competitive removal behavior of As(III, V) species and organic ligands in the water treatment process.

Optimization of Antimony Removal by Coagulation-Flocculation-Sedimentation Process Using Response Surface Methodology

“…The predetermined amount of FC coagulant was added and a small quantity of 0.1 M HCl and 0.1 M NaOH solution was added to adjust the pH. A jar tester apparatus with six beakers (Model: SJ-10, Young Hana Tech Co., Ltd., Gyeongsangbuk-Do, Korea) was used to conduct the C/F/S experiments at a temperature of 25 ± 1 • C. C/F/S experimental conditions included a rapid coagulation at 140 rpm for 3 min, a flocculation at 40 rpm for 20 min, a sedimentation for 30 min, and a filtration using a 0.45 µm glass fiber filter [14][15][16][17][18]. Aliquots (50 mL) were collected after the filtration process and stored in the dark at 4 • C for further analysis.…”

“…A stock solution of Fe(III) was prepared at 500-5000 mg/L by dissolving FeCl 3 •6H 2 O in DI water for further dilution to obtain the desired Fe(III) concentrations for a particular experimental run. A stock solution of model organic matter was prepared at 0.1 g C/L by dissolving humic acid in DI water following a similar procedure as described in our previous studies [14,17,18]. In order to avoid the interference of unwanted contaminants, all glass vessels and glassware were initially washed with 15% HNO 3 solution followed by rinsing with DI water.…”

“…Furthermore, it is necessary to optimize the treatment efficiency of the C/F/S process by taking into consideration the concentration and characteristics of Sb species in order to achieve high Sb coagulation efficiency. The jar test procedure has been extensively employed to optimize Sb removal performance by a C/F/S process [11,12,[14][15][16][17][18]. This classical approach is also referred to as the one-factor-at-a-time method, changing the level of one factor while keeping other factors constant.…”

Effect of Water Chemistry on Antimony Removal by Chemical Coagulation: Implications of ζ-Potential and Size of Precipitates

“…The pH was adjusted to predetermined levels for each experiment using either 0.1 M HCl or 0.1 M NaOH solutions. The coagulation experiments were conducted for each of the experimental conditions according to the following three sequential steps: coagulation via rapid mixing at 140 rpm for 3 min, flocculation via slow mixing at 40 rpm for 20 min and quiescent settling for 30 min [11,12,13,28]. The sample was then collected to measure the ζ-potential and HDD of early formed FC precipitates.…”

Synthesis and Characterization of Novel Hybrid Flocculants Based on Potato Starch Copolymers with Hollow Carbon Spheres

“…Unfortunately, during application of traditional waste water treatment agents the remaining of metal ions originating from inorganic coagulants and unreacted monomers from polymeric compounds are of major concern [ 11 , 12 , 13 , 14 , 15 ]. Therefore, a development of new water purification agents with comprehensive activity (e.g., dual functionality-flocculation and antibacterial action [ 16 , 17 , 18 ], coagulation and flocculation [ 19 , 20 , 21 , 22 ]), and/or containing natural polymers [ 23 , 24 , 25 , 26 ] or hybrid materials [ 27 , 28 , 29 , 30 ] is justified from a scientific, practical, and economic point of view.…”