Testing of Chemically Activated Cellulose Fibers as Adsorbents for Treatment of Arsenic Contaminated Water.

Mihaela Ciopec,Petru Negrea,Sergiu Coseri,Makarand Ghangrekar,Adina Negrea,Narcis Duțeanu,Gabriela Biliuta

doi:10.3390/ma14133731

Abstract

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Therefore, it is important to remove arsenic from aqueous solutions. Among many arsenic removal technologies, adsorption offers a promising solution with a good efficiency, however the material used as adsorbent play a very vital role. The present investigation evaluated the behavior of two cellulose-based adsorbent materials, i.e., viscose fibers (V) and its TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) derivative, obtained by using the well-established TEMPO-mediated protocol (VF). Due to the known arsenic affinity for Fe ions the two materials were later doped with it. This was done after a preliminary functionalization with di-2-ethylhexyl phosphoric acid (DEHPA), to obtain two materials: V-DEHPA-Fe and VF-DEHPA-Fe. Arsenic adsorption is known to be pH dependent (between 6 and 8); therefore, the optimal pH range for As(V) adsorption has been established. In order to evaluate the adsorption mechanism for both the synthesized materials, the influence of contact time, temperature and initial concentration was evaluated. Langmuir, Freundlich and Sips equilibrium isotherm models were used in order to determine the ability of the model to describe As(V) adsorption process. The maximum adsorption capacity of the material V-DEHPA-Fe was 247.5 µg As(V)/g with an As(V) initial concentration of 5 mg/L and for the material VF-DEHPA-Fe it was 171.2 µg As(V)/g with initial concentration of 5 mg/L.

Highlights

Exposure to different arsenic concentrations, either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health
TEMPO-mediated oxidation of viscose fibers allows the formation of significant amounts of 6-carboxy cellulose, with increasing amount from 6 mmol/kg in the unoxidized sample to 280 mmol/kg in the oxidized sample, as determined by using potentiometric titration [81,87]
The results reported in this study have shown that the new adsorbent materials obtained from functionalization of synthesized viscose with di-2-ethylhexyl phosphoric acid (DEHPA) and Fe(III) ions are effective for increasing As(V) removal efficiency from aqueous solutions

Summary

Introduction

Exposure to different arsenic concentrations (higher than 10 μg/L), either due to the direct consumption of contaminated drinking water or indirectly by using contaminated food is harmful for human health. Technologies are being developed for removing arsenic from water, such as, coagulation [14,15,16,17,18], oxidation [17,19], reverse osmosis [17,20,21,22], ion exchange [14,15,17,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49], electrocoagulation [50,51,52], adsorption onto fine and coarse iron oxides [53,54] and other materials including iron impregnated activated carbon and natural arsenic adsorbents [17,33,36,37,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70]. The use of natural polymers as an adsorbent material for arsenic removal from water is drawing special attention [72,73,74,75,76,77]

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