Article pubs.acs.org/IECR
Chitosan- and Iron−Chitosan-Coated Sand Filters: A Cost-Effective Approach for Enhanced Arsenic Removal Anjali Gupta,†,‡ Mohammed Yunus,‡ and Nalini Sankararamakrishnan*,† †
Center for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur U.P. 208016, India Babasaheb BhimRao Ambedkar University, Lucknow, U.P., India
‡
S Supporting Information *
ABSTRACT: This paper describes the potential of chitosan-coated sand (CCS) and iron−chitosan-coated sand (ICCS) toward the removal of both As(V) and As(III) from aqueous systems. Various parameters including pH, equilibration time, initial arsenic concentration, and adsorbent dosage have been optimized for maximum adsorption. The adsorption data fitted well in both Langmuir and Freundlich adsorption models. The Langmuir monolayer adsorption capacity was found to be 17 and 23 mg/g for CCS and 26 and 56 mg/g for ICCS at pH 7 for As(III) and As(V), respectively. The reaction followed a pseudo-first-order model. Column studies revealed higher breakthrough capacity for As(V) using both CCS and ICCS. Adsorption plots were fitted with BDST model. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to 0.977) and Freundlich model (R2 = 1), which interpreted the adsorption process fitted to a monolayer adsorption on a
(3)
Table 1. Langmuir and Freundlich Model Constants
where Co and Ce are the amount of initial arsenic species taken in the solution and amount of arsenic adsorbed at pseudo equilibrium condition and at time t, respectively, and K is the adsorption rate constant. The rate constants for As(V) and As(III) using CCS were found to be 1.0948 and 0.38078 h−1, respectively. In the case of ICCS the values obtained for the rate constants were 0.7572 and 1.6097 h−1 for As(III) and As(V), respectively.
Langmuir model adsorbents CCS ICCS
2069
Freundlich model
arsenic species
Qmax (mg/g)
b (mL/mg)
R2
1/n
Kf
R2
As(III) As(V) As(III) As(V)
17 23 26 56
1.144 1.016 1.09 1.04
0.817 0.946 0.986 0.977
1 1 1 1
2.49 2.49 2.50 2.50
1 1 1 1
dx.doi.org/10.1021/ie302428z | Ind. Eng. Chem. Res. 2013, 52, 2066−2072
Industrial & Engineering Chemistry Research
Article
homogeneous surface. The Freundlich parameters for n value were both higher than 2.4, indicated that arsenic was favorable to adsorption on adsorbents. It can be seen from the values of Qmax (mg g−1) in Table 1 that the maximum adsorption capacities obtained for ICCS were 26 and 56 mg g−1 and for As(III) and As(V), respectively, at pH 7, which was much higher than that for CCS. Compared with other adsorbents in Table 2, the adsorption capacities of CCS and ICCS are more Table 2. Comparison of Adsorption Capacities of Some Adsorbents toward Arsenic Removal (pH is Shown in Parantheses) capacity obtained from Langmuir model (mg/g) adsorbents
As III
As V
refs
goethite hematite ferrihydrite Fe and Mn oxide-coated sand FeS-coated sand iron oxide-coated sand zerovalent iron-coated sand chitosan-coated sand Fe−chitosan-coated sand
10.1 (7.5) 10.0 (7.3) 0.58 (4.2) 0.129 (7.2) 10.7 (7) 0.136 (7.6) 70.4 (7.0) 17 (7) 26 (7)
12.1 (7.5) 31.3 (7.3) 0.16 (9.2) 23 (7) 56 (7)
30 30 31 32 33 34 35 present work present work
Figure 6. Breakthrough curves of arsenite and arsenate using CCS and ICCS. Conditions: inlet concentration of As(V)/As(III) 500 μg/L, flow rate 2 mL/min, pH 7.
arsenic concentration from 500 μg L−1 to
