Synthesis of Minerals with Iron Oxide and Hydroxide Contents as a Sorption Medium to Remove Arsenic from Water for Human Consumption

Abstract

Arsenic has been classified as a toxic and carcinogenic chemical element. It therefore presents a serious environmental problem in different regions of the country and the world. In the present work, two adsorbent media were developed and evaluated to remove arsenic from water in the Pájaro Verde mine shaft, Huautla, Tlaquiltenango, Morelos. The media were synthesized and characterized, obtaining a surface area of 43.04 m2·g−1 for the goethite and 2.44 m2·g−1 for silica sand coated with Fe(III). To conduct the sorption kinetics and isotherms, a 23 factorial design was performed for each medium in order to obtain the optimal conditions for the factors of arsenic concentration, pH and mass of the adsorbent. The best results were obtained for goethite, with a removal efficiency of 98.61% (C0 of As(V) 0.360 mg·L−1), and an effluent concentration of 0.005 mg·L−1, a value that complies with the modified Official Mexican Standard NOM-127-SSA1-1994 [1] and WHO guidelines (2004) [2]. The kinetic equation that best fit the experimental data was the pseudo-second-order, resulting in the highest values for the constants for synthetic goethite, with a rate constant sorption of 4.019·g·mg−1·min−1. With respect to the sorption isotherms, both media were fitted to the Langmuir-II linear model with a sorption capacity (qm) of 0.4822 mg·g−1 for goethite and 0.2494 mg·g−1 for silica sand coated with Fe(III).

Influences of pH on transport of arsenate (As5+) through different reactive media using column experiments and transport modeling

“…In general, the sorption capacity in the present study (column study) was 0.022-0.083 mg/g and 0.117-0.131 mg/g for IOCS and ZVICS-IOCS columns, respectively. Our results fell between 0.008 and 0.249 mg/g, which were obtained for IOCS in other studies [16][17][18]23,24 . However, those results were obtained from batch studies.…”

“…The fitted TSM breakthrough curves from the HYDRUS-1D model concerning the fraction of instantaneous sites (f) and the first kinetic sorption rate of As(V) onto IOCS at pH 4 and 7 ( Fig. 3(c,d)) describe a better description of As(V) sorption onto IOCS, which indicates that As(V) could sorb onto both instantaneous sorption sites and kinetic sorption sites 24 . The Freundlich constant (Kf) decreased as pH increased from 4 to 7 for As(V) migration through the ZVICS-IOCS columns, which agrees with the decreased retardation factor (RF) from 37.18 to 13.78, respectively, (see Table 2) because at pH 4 the surface charge of IOCS became more positively charged.…”

“…Recently, innovative technologies, such as coating iron-oxide onto sand surfaces, have become of interest because they are commonly inexpensive and have high efficiencies for the removal of heavy metals from contaminated water (i.e., Cr(VI), Pb(II), Cu(II), As(III)) [15][16][17][18] . Past research on the use of individual reactive materials such as granulated iron hydroxide (GIH), ferrihydrite-coated sand, IOCS, sulfate modified iron oxide-coated sand (SMIOCS) and ZVI [16][17][18][19][20][21][22][23][24] , for the removal of heavy metals has mainly focused on batch experiments 25 rather than flow-through systems or column experiments that can be applied for in situ remediation, such as the permeable reactive barrier (PRB) technique. Furthermore, Das et al 26 found that three ZVI materials can be used to effectively remove Se(VI) in batch testing and the process is influenced by other anions, SO 4 2− and NO 3 − .…”

Effects of Sulfate, Chloride, and Bicarbonate on Iron Stability in a PVC-U Drinking Pipe

“…Iron release from metal pipes could be one of the sources of iron in DWDSs [11,22]. Meanwhile, the use of iron flocculants during water treatment was also found to be a source of iron [23,24]. As a result, the PVC-U pipes could be considered as a source of secondary iron pollution, thus affecting drinking water quality.…”