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Adsorption of As(III) from aqueous solutions by iron oxide-coated sand

“…The observed maximum adsorption efficiency at pH 7.5 was 9.8%. Similar results had also been obtained earlier [24] using iron oxide-coated sand: removal of As(III) and As(IV) was greater than 95% in the pH range 5 to 7.6 after 6 h of contact time with an initial arsenic concentration of 100 µg/l. Maximum As(III) uptake was observed at pH 7.5, and hence all further experiments were carried out at pH of 7.5. that with iron-coated sand, adsorption efficiency increases rapidly with an increase in contact time up to 120 min; and a maximum removal efficiency of 93% was achieved and remained fairly constant up to the end of the experiment (180 min).…”

“…Batch studies [23] have been performed using iron oxide-coated sand and ferrihydrite with natural water containing 325 µg/l arsenic, and the removal of 90% of the arsenic was observed. The application of iron oxide-coated sand-2 prepared by a high-temperature coating process has been demonstrated in batch and column studies [24] to remove As(III) and As(IV) to a level less than 5 µg/l at pH 7.6 in drinking water with an initial arsenic concentration of 100 µg/l. Though adsorption of arsenic on iron-coated sand has been studied by many workers, the information available is limited and more testing is necessary.…”

Adsorption of arsenate and arsenite on titanium dioxide suspensions

“…The kinetics and amounts of As(V) adsorption onto TiO 2 suspensions were pH dependent; higher rates and amounts adsorbed occur at low pH. Similar pH dependence on the uptake of As(V) onto other oxide surfaces was found [8][9][10][11][12]17,18]. The As(V) adsorption kinetic data were found to be best described by the power function kinetic model [19], which can be described by the equation…”

Fotocatálise heterogênea com TiO2 para oxidação de arsênio e sua remoção de águas por coprecipitação com sulfato férrico

“…11,12 Dessa forma, o As(III) deve ser oxidado a As(V) para ser removido com sais de ferro(III). 4,[11][12][13][14] A oxidação pode ser realizada por oxidantes tais como oxigênio, ozônio, reagente Fenton, peróxido de hidrogênio, cloro, permanganato ou dióxido de manganês sólido etc. 12,15 Entre os processos de descontaminação ambiental que estão sendo desenvolvidos, os chamados "Processos Oxidativos Avança-dos" (POA) vêm atraindo grande interesse pela formação de radicais hidroxila (  OH), agente altamente oxidante.…”