Adsorption of nitrate and nitrite anion by modified maize stalks from aqueous solutions.

The newly developed aminated maize stalk (AMS) was prepared by a chemical process using charred maize stalk (CMS). The AMS was used for the removal of nitrate and nitrite ions from aqueous media. The effects of initial anion concentration, contact time, and pH were studied by the batch method. The prepared adsorbent was characterized by FT-IR, XRD, FE-SEM , and elemental analysis. The concentration of the nitrate and nitrite solution before and after was determined with the help of a UV-Vis spectrophotometer. The maximum adsorption capacities were found to be 294.11 mg/g for nitrate and 232.55 mg/g for nitrite, respectively, at pH 5 for both ions attaining equilibrium within 60 min. The BET surface area of AMS was found to be 25.3 m2/g with a pore volume of 0.02cc/g. The pseudo-second-order kinetics model fit well, and the adsorption data supported the Langmuir isotherm. The findings revealed that AMS has a high capability for removing nitrate (NO3-) and nitrite (NO2-) ions from their aqueous solutions.

Comparative study of Hg(ii) biosorption performance of xanthated and charred sugarcane bagasse from aqueous solutions.

The main target of this study was to evaluate the efficiency of charred xanthated sugarcane bagasse (CXSB) and charred sugarcane bagasse (CSB) in the removal of Hg(ii) ions from aqueous media. Batch experiments were performed to study the experimental parameters such as effects of pH, concentration, contact time and temperature. The adsorption velocity of Hg(ii) onto CSB and CXSB was fast and reached equilibrium within 60 minutes. Isotherm and kinetic studies showed that Hg(ii) uptake using both the biosorbents followed Langmuir isotherm and pseudo second order kinetics. The maximum adsorption capacity of Hg(ii) at optimum pH 4.5 onto CSB and CXSB was found to be 125 mg g-1 and 333.34 mg g-1, respectively. A negative value of ΔG° and positive ΔS° value (0.24 kJ mol-1 for CSB and 0.18 kJ mol-1 for CXSB) for both the biosorbents confirm the spontaneous nature of Hg(ii) adsorption. A positive value of ΔH° (52.06 kJ mol-1 for CSB and 30.82 kJ mol-1 for CXSB) suggests the endothermic nature of biosorption. The investigated results shows that CXSB compared to CSB can be used as a low cost and environmentally benign bio-adsorbent for the removal of Hg(ii) ions from aqueous solutions.

Adsorption and removal of crystal violet dye from aqueous solution by modified rice husk.

An approach to removing crystal violet (CV) dye from aqueous solutions was investigated by introducing a xanthate group on charred rice husk. The newly prepared charred rice husk (CRH) and xanthated rice husk (XRH) were characterized by XRD, SEM, FTIR, and elemental analysis. A batch technique was used to adsorb CV dye in aqueous suspensions. Different adsorbent quantities, concentrations, pH, and contact times were investigated to find the effect of these parameters. The optimum pH for both CRH and XRH was found to be 10. The adsorption capacity of CV dye onto CRH and XRH was found to be 62.85 mg/g and 90.02 mg/g at pH10, respectively. Langmuir isotherms could be reasonably explained by the experimental data. Within 60 min, equilibrium was achieved. Similarly, the kinetic data are best suited to the pseudo-second-order model. In comparison to XRH with CRH, XRH was found more efficient and can be used as a feasible alternative for removing CV dye from aqueous solutions.