Simultaneously removal of inorganic arsenic species from stored rainwater in arsenic endemic area by leaves of Tecomella undulata: a multivariate study

In the present study, an indigenous biosorbent (leaves of Tecomella undulata) was used for the simultaneous removal of inorganic arsenic species (As-III and As-V) from the stored rainwater in Tharparkar, Pakistan. The Plackett-Burman experimental design was used as a multivariate strategy for the evaluation of the effects of six factors/variables on the biosorption of inorganic arsenic species, simultaneously. Central composite design (CCD) was used to found the optimum values of significant factors for the removal of As-III and As-V. Initial concentrations of both inorganic As species, pH, biosorbent dose, and contact time were selected as independent factors in CCD, while the adsorption capacity (q(e)) was considered as a response function. The separation of inorganic As species in water samples before and after biosorption was carried out by cloud point and solid-phase extraction methods. Theoretical values of pH, concentration of analytes, biosorbent dose, and contact time were calculated by quadratic equation for 100% biosorption of both inorganic As species in aqueous media. Experimental data were modeled by Langmuir and Freundlich isotherms. Thermodynamic and kinetic study indicated that the biosorption of As-III and As-V was followed by pseudo second order. It was concluded that the indigenous biosorbent material efficiently and simultaneously removed both As species in the range of 70.8 to 98.5 % of total contents in studied ground water samples.