Development of sustainable magnetic chitosan biosorbent beads for kinetic remediation of arsenic contaminated water

https://doi.org/10.1016/j.ijbiomac.2020.06.287Get rights and content

Highlights

  • We synthesized Fe3O4 NPs mediated chitosan beads as biosorbent for As removal from water.

  • Purpose was to enhance As removal efficiency and reusability of the resultant biosorbent.

  • The sorption of As species on the prepared beads obeyed pseudo-second order kinetics.

  • Langmuir's isotherm best-fitted on the data based on high linear regression coefficient (R2 > 0.999).

  • The prepared beads could be used as biosorbent for effective As removal from water.

Abstract

We report the preparation of both control chitosan and magnetic chitosan beads as biosorbents using chitosan as matrix and magnetite (Fe3O4) nanoparticles as reinforcement followed by detailed advanced characterization. The batch trials were performed to study the adsorption kinetics of biosorbents by removing As(III) and As(V) species from water systems. The experimental data was inserted into Langmuir and Freundlich's isotherms to undertake the mechanism and adsorption capacity of the test biosorbents. Under Langmuir's isotherm, maximum monolayer adsorption capacity (qmax) of the biosorbent was observed to be 73.69 and 79.49 mg/g for As(III) and As(V) species, respectively, under specified conditions. The optimum doses of 1.5 and 2 g/L of MCBB at pH 6.7 showed 99.5 and 99% removal of As(V) and As(III), respectively. The analysis demonstrated that the biosorption process obeyed pseudo 2nd order kinetics with linear regression coefficient (R2) of >0.999. The regeneration and reusability of biosorbents were also assessed.

Introduction

Water has been considered as an important element for the existence and survival of life on the biosphere. However, it is being continuously contaminated by human activities, radioactive isotopes, oil spillages, industrial effluents and the agricultural runoffs [1]. Water pollution produced by heavy metals and metalloids (such as Cd, Hg, Pb and As) has badly affected the health of millions of people due to their prevalence in drinking water [2]. Among various contaminating metal ions, arsenic, due to its high toxicity and mobility, is considered as carcinogenic and among the most hazardous ones. Arsenic contamination can originate either from anthropogenic activities like wood preservatives, electronic industries, pesticides and minings or from natural processes like weathering and erosion of arsenic containing rocks. In either case, in aqueous media, arsenic usually exists in two inorganic forms i.e., trivalent arsenite and pentavalent arsenate oxyanions usually designated as As(III) and As(V) respectively, being considered major arsenic species whereas monomethylarsenic acid and deimethylarsenic acid to be minor components - all being responsible for accumulative water contamination. Arsenic poisoning of potable water is incredibly inconvenient for the human health. According to current guideline of World Health Organization, the acceptable level of arsenic concentration in potable water is 10 μg/L [3]. Drinking of arsenic poisoned water can cause several diseases in human beings. More than 220 million people are threatened all over the world because of arsenic in drinking water. Such chronic exposure to inorganic arsenic leads to various biological disorders related to digestive, endocrine, neurological, hematopoietic and reproductive systems that eventually cause cancer [4].

Different adoptable techniques have been emerged for the treatment of arsenic contaminated water include membrane filtration, ion-exchange, chemical precipitation and adsorption [5]. Among the existing technologies, the one based on adsorption has been demonstrated as the best available approach and of great potential due of its versatility, low cost, simplicity in operation, low energy requirements and the maintenance of operating system [6]. An ideal adsorbent possesses high adsorption capacity, large surface area, suitable volume and pore size, compatibility and mechanical stability for the treatment of polluted water. Having the advantages of high safety, low toxicity, abundance, better chemical reactivity, physical and chemical versatilities, chitosan is mainly used for the removal of pollutants through adsorption mechanism.

Chitosan is notable as a magnificent biosorbent for heavy metal ions removal, because it possesses a novel blend of properties like biocompatibility, bioactivity, biodegradability, nonpoisonous and renewability It is obtained by the deacetylation of chitin, the second most abundant polysaccharide after cellulose present in the nature [7]. However, it experiences some shortcomings i.e., low porosity and surface areas, low thermal stability, mechanically weakness, low stability in the acid media, resistance to mass transfer, which bring about low adsorption rate with respect to contaminants present in the water system. To mitigate these shortcomings, some research groups have modified the chitosan matrices through physical approaches like shaping them into beads, membranes, flakes, threads, hollow fibers and sponges through chemical approaches including crosslinking, grafting and metals NPs incorporation for some specific applications like sequestering of metal and metalloid ions from water system [8].

As compared to other nanomaterials like zero valent nano‑iron, Fe2O3 and TiO2 etc., Fe3O4 as a nanomaterial has gained much interest in arsenic contaminated water treatment systems due to its magnetic property, biocompatibility, cost effective, surface modifiability, high affinity for arsenic compounds, and the most important being low-toxic [9]. The incorporation of Fe3O4 NPs into chitosan beads makes them mechanically strong even in acidic media, reduces their swelling property, makes nonporous chitosan beads being porous, increases the surface area and also functionalizes the surface of the beads which ultimately enhances its adsorption capacity for arsenic uptake [10]. In addition, Fe3O4 NPs show strong affinity towards arsenic uptake and their magnetic property makes it easy to separate the magnetized biosorbent out from the aqueous system under external magnetic field after utilization [11].

Although, Fe3O4 NPs had been used with other biomaterials for environmental applications yet we reviewed the literature and analyzed that the Fe3O4 NPs mediation in chitosan beads for removal of both trivalent and pentavalent arsenic species from aqueous media had rarely been reported with so much adsorption capacity and fast adsorption rate.

The novelty in this study is expressed as the sustainable, reusable and stable magnetic chitons biosorbent beads (MCBB) have been prepared by incorporation of Fe3O4 NPs, without adding any cross-linkers. The purpose was to effectively utilize the single bondOH and single bondNH2 functional groups of chitosan by modification to enhance the arsenic removal efficiency with viable reusability and minimum leaching of Fe3O4 NPs in the bath under desirable conditions. The arsenic adoption kinetics and mechanism from aqueous media were investigated using Langmuir and Freundlich's isotherms by tuning various parameters including pH, PZC, initial arsenic concentration, adsorbent dose, contact time, and the Fe3O4 NPs contents in the beads prepared. The prepared sorbent beads were undertaken for regeneration and reusability for multiple cycles. Being reusable and easily recoverable, the developed biosorbent beads expressed their efficiency as potential candidate for environmental and industrial water purification systems especially in the regions where the quality of underground water is poor.

Section snippets

Materials

Chitosan (degree of deacetylation: 95.0%, molecular mass: 1526.464 g/mol) was purchased for MP Biomedicals, LLC, France. Other analytical grade chemicals include, sodium hydroxide (NaOH, 99%), sulphuric acid (H2SO4, 95–98%) and sodium nitrate (NaNO3, 99%), sodium tetrahydridoborate (NaBH4), were purchased from Merck, Germany. Poly(ethylene glycol) (PEG) average Mn 20,000, hydrogen peroxide (H2O2), ethanol (C2H6O) and sodium arsenate dibasic heptahydrate (Na2HAsO4.7H2O, ≥98%) were purchased from

Profile of Fe3O4 nanoparticles

The TEM image of Fe3O4 NPs has shown in Fig. 2a. It has been observed from the TEM image that the Fe3O4 NPs were of average diameter 39 nm having spherical morphology. The Fe3O4 NPs has shown agglomeration which might be due to presence of strong attractive forces among the magnetic NPs. Tazikeh et al. [15], in their study, observed that the Fe3O4 NPs agglomeration due do presence of van der Wall's forces among them.

One of the important parameters to characterize a nanomaterial is to determine

Conclusions

In the present study, we have successfully prepared the CCBB and MCBB using sol-gel method. The structure and the adsorbing property of the MCBB were thoroughly investigated under various parameters. The impregnation of Fe3O4 NPs has not merely increased the BET surface area of MCBB but also has increased their adsorption capacity by exposing the single bondOH and single bondNH2 function groups for arsenic binding. The sorption capacity of Fe3O4-modified beads was much higher compared to control chitosan beads. The

Declaration of competing interest

The authors declare neither present nor potential conflict of interest with the study reported here.

Acknowledgment

The authors acknowledge the financial support (as NRPU-9566) from the Higher Education Commission, Pakistan for completion of this study.

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