Fixed-Bed Column Adsorption of Arsenic(v) by Porous Composite of Magnetite/Hematite/Carbon With Eucalyptus Wood Microstructure

Abstract

The fixed-bed column adsorption-desorption of As(V) by the porous composite of iron oxides and carbon with eucalyptus wood hierarchical microstructure (PC-Fe/C) was experimentally studied. The increase in the influent As(V) concentration and the inflow rate resulted in an earlier exhaustion of the column. The breakthrough curves indicated that a larger adsorbent mass, a smaller adsorbent grain size and a lower influent pH prolonged the column life span. The operating temperature had negligible effect. All breakthrough curves could be well fitted with the Thomas and Yoon–Nelson models. Under the condition of the influent flow rate of 5.136 mL/min, the influent As(V) concentration of 20 mg/L, the influent pH of 3, the adsorbent mass of 2 g, the adsorbent grain size of <100 mesh, and the operating temperature of 35 °C, the equilibrium adsorption capacity reached 10.49 mg/g, which was greater than those of natural/synthetic iron oxides adsorbents and iron-oxide-coated adsorbents.

Dissolution and Solubility of the Synthetic Natroalunite and the Arsenic-Incorporated Natroalunite at pH of 2.00–5.60 and 25–45°C

“…6 , respectively. e precipitates almost always had an apparent Al deficiency in the B 3+ sites and an appreciable Na deficiency in the A + sites (7∼12%) of the natroalunite AB 3 (TO 4 ) 2 (OH) 6 . e latter might reflect an incorporation of H 3 O + to form a solid solution that was hardly proved since H 3 O + cannot be measured directly using microprobe technique or wet chemistry [34].…”

“…e Debye-Hückel equations were applied in the PHREEQC calculation since all solution ionic strengths in the present experiment were lower than 0.023 mol/L. 6 , respectively. e precipitates almost always had an apparent Al deficiency in the B 3+ sites and an appreciable Na deficiency in the A + sites (7∼12%) of the natroalunite AB 3 (TO 4 ) 2 (OH) 6 .…”

“…where {} is the thermodynamic activity and K sp is the solubility product according to the dissolution reactions (1) and (4 6 ], can also be estimated by the use of the following thermodynamic data in the literature [46,47] e calculated solubility products together with the total dissolved concentrations of sodium, aluminum, arsenic, and sulfur including solution pHs in the last three equilibrated solutions (5760 h, 6480 h and 7200 h) are given in Table 1 for the synthetic natroalunite and Table 2 for the synthetic arsenic-incorporated natroalunite.…”

“…Its high levels in air, water, and soil can result from a combination of human activities and natural processes [3,4]. Arsenic is commonly found in mine waters and solid wastes from nonferrous metal mining and metallurgy, and many researchers have made efforts to develop techniques to eliminate and stabilize this toxicant, but it is still a very great challenge for nonferrous metal industries [5,6]. Information about the processes controlling arsenic in environments is needed to predict its distribution in different phases.…”

“…Recently, many scholars aim to study the AsO 4 -for-SO 4 replacement in natroalunite [NaAl 3 (SO 4 ) 2 (OH) 6 ], a member of the alunite supergroup [AB 3 (TO 4 ) 2 (OH,H 2 O) 6 ] that exists in oxidizing, acidic, and S/Al-rich environments, and it is very common and extremely stable in nature [19,20]. e ideal natroalunite has a common formula of NaAl 3 (SO 4 ) 2 (OH) 6 , made up of linear tetrahedral-octahedral-tetrahedral (T-O-T) laminas, where the Na + ion sites with an AO 6 (OH) 6 icosahedra coordination and the Al 3+ and SO 4 2− ion sites with slightly distorted AlO 6 octahedra (O) and SO 4 tetrahedral (T) coordinations, respectively [21]. e A sites are commonly filled by K + , Na + , and H 3 O + , the B sites by Fe 3+ and Al 3+ , and the TO 4 sites by SO 4 2− , PO 4 3− , and AsO 4 3− , respectively.…”