Removal of Arsenic and Phosphate from Aqueous Solution by Metal (Hydr-)oxide Coated Sand

Abstract

Arsenic contamination is a major concern in many drinking water supplies around the world. One low-cost approach for removing arsenic and other oxyanions such as phosphate is to use metal (hydro-)oxide coated sands. In this study, solution pH, sand grain size, coating efficiency, and mineral type for iron-coated sand (ICS), manganese-coated sand (MCS), and iron-and manganese-coated sand (IMCS) were evaluated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to investigate the surface properties of the coated layer. The mineral type of ICS prepared at different solution pH was identified as a mixture of FeOOH and Fe 2 O 3 . The mineral type of MCS prepared at pH 4 and 7 was identified as MnO 2 and changed to ramsdellite (γ-MnO 2 , a mixture of α-MnO 2 and β-MnO 2 ) at pH 10. ICS exhibited a greater phosphate removal capacity, and phosphate removal increased with increasing iron oxide on the sand. ICS was also shown to have a greater removal capacity for phosphate than chemical precipitation methods by FeCl 3 , especially below neutral pH. In contrast, IMCS(Fe:Mn = 7:3) was better for removing As(III), which occurs through oxidation to As(V) and adsorption of As(III) and As(V) and can reach >98% removal rate (residual concentration <0.02 mg/L) at neutral pH. IMCS(7:3) is an efficient adsorbent for arsenic, as >50% can be removed within 60 min; 66% adsorption was reached after 24 h. Removal of arsenic and phosphate by these metal (hydro-)oxide coated sand adsorbents followed a pseudo-second-order rate and Langmuir as well as Freundlich adsorption isotherms. Removal under different conditions (e.g., pH, ionic strength) was also evaluated to provide information to optimize the process.

Engineered nanomaterials for water treatment and remediation: Costs, benefits, and applicability

“…Various adsorption methods tend to be effective across the board at removing most pollutants, both organic [75,87, and inorganic [176][177][178][179][180][181][182][183][184]. Most adsorption methods use a carbonaceous material to trap pollutant molecules inside its pore structure [148,[185][186][187][188][189][190][191][192][193][194][195][196].…”

Influence of Extracellular Polymeric Substances on the Long-Term Fate, Dissolution, and Speciation of Copper-Based Nanoparticles

“…Copper content (wt %) of particles was determined via ICP-AES (iCAP 6300, Thermo Scientific). Further characterizations were done via X-ray diffraction (XRD, Bruker D8 Advance), 18 X-ray photoelectron spectroscopy (XPS, Kratos Axis Ultra), thermogravimetric analysis (Mettler STARe TGA/ sDTA851e), Brunau−Emmet−Teller (BET) surface area analysis (Micromeritics TriStar 3000 porosimeter), helium density analysis (Micromeritics AccuPyc II 1340 pycnometer), and scanning electron microscopy (FEI XL30 Sirion equipped with an EDAX APOLLO X probe for energy-dispersive X-ray spectroscopy, EDS).…”

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…Engineered nanomaterials (ENMs) are now being widely manufactured and used in medicines, personal care products [17], clothing, coatings and paints, electronics, food supplements and food packaging [2], and environmental protection [8,12,[18][19][20][21]. It is very likely that the large amount of production of ENMs will lead to their release into the environment through production, application, and disposal processes [1,22,23].…”