Efficient removal of Cr (VI) from aqueous solution by using tannery by-product (Buffing Dust).

The current study is focused on using tannery waste called buffing dust to remove hexavalent chromium from an aqueous solution. The buffing dust was characterised by using different technique like FTIR, SEM, and BET analysis. The adsorption experiment was conducted in batch mode. The different operating factors including contact time, dose and initial Cr (VI) concentration were investigated. The optimum adsorption capacity was observed at contact time of 240 min and dose of 1g/100 mL. The adsorption isotherm such as Langmuir, Freundlich and Temkin were investigated at different initial concentration. It was observed that Langmuir isotherm model was best fitted for present study with maximum adsorption efficiency of 11.33 mg/g. The kinetic study was performed for pseudo first order and pseudo second order and it was found that pseudo second order model was provided the best match with regression coefficient (R2) of 0.9991.

Floodplains landforms, clay deposition and irrigation return flow govern arsenic occurrence, prevalence and mobilization: A geochemical and isotopic study of the mid-Gangetic floodplains.

This article attempts to understand the evolution of groundwater chemistry in the mid Gangetic floodplain through the identification of hydrogeochemical processes including the impact of surface recharge and geological features. Isotopic investigations identified that irrigation return flow is partly responsible for arsenic (As) enrichment through preferential vertical recharge. Further, the floodplain geomorphological attributes and associated As hydrogeochemical behaviour traced through isotopes tracers highlighted that meandering and ox-bow like geomorphological features owing to clay deposition leads to the anoxic condition induced reductive microbial dissolution of As-bearing minerals causing the arsenic contamination in the investigated aquifer of the mid-Gangetic plain (MGP). To achieve the objectives, 146 water samples for water chemistry and 62 samples for the isotopic study were collected from Bhojpur district, Bihar (district bounded by the river Ganges in the north and Son in the east) located in MGP during the pre-monsoon season of 2018. The chemical results revealed high arsenic concentration (BDL to 206 µg.L-1, 32% samples are exceeding the 10 µg.L-1 limit) in the Holocene recent alluviums which are characterized by various geomorphological features such as meander scars and oxbow lake (northern part of the district). Arsenic is more concentrated in the depth range of 15-40 m below ground surface. All other trace metals viz. Ni, Pb, Zn, Cd and Al were found in low concentration except Fe and Mn. The geochemical analyses suggest that rock-water interaction is controlling the hydro-geochemistry while the chemical constituent of the groundwater is mainly controlled by carbonate weathering with limited contribution from silicate weathering. The isotopic signatures revealed that the Son river is recharging groundwater while the groundwater is contributing to the Ganges river. A clear pattern of fast vertical recharge in the arsenic contaminated area is observed in the proximity to the river Ganges with an elevated nitrate concentration resulted from the reduced As dissolution. The origin of groundwater is local precipitation with low to high evaporation enrichment effect which is further indicating the vertical mixing of groundwater from the irrigation return flow and/or recharge from domestic discharge causing enhanced As mobilization through microbial assisted reductive dissolution of As-bearing minerals.

Removal mechanism of cationic dye (Safranin O) from the aqueous phase by dead macro fungus biosorbent.

Batch biosorption parametric experiments were carried out to delineate the removal mechanism of cationic dye, namely, Safranin O, from the aqueous phase using biosorbent prepared from wood rotting dead macro fungus 'Fomitopsis carnea'. Experimental data of the kinetic experiments at various temperatures (19, 27 and 35 °C) were well described using pseudo-second order kinetic models. Raising temperature from 19 to 35 °C enhanced the dye uptake potential of the biosorbent from 1,000 to 1,250 mg/g. The other variables studied were the effect of common salt (NaCl) and pH on the dye removal potential of the biosorbent. Decreased dye removal (%) efficiency at higher salt concentration suggests involvement of an ion-exchange type sorption mechanism. The pH study revealed that dye removal may occur due to the existence of an electrostatic attraction force between negatively charged biosorbent particles and dye cation. However desorption using mineral acid (H2SO4 and HCl) exhibited the highest desorption up to 76%, followed by organic acid (52%) and distilled water (not more than 2%) indicating the possibility of ion-exchange as the dominating dye sorption mechanism. Fourier transform infrared (FT-IR) spectroscopy analysis of the biosorbent, Safranin O and Safranin O loaded biosorbent also supported the possibility of ion-exchange as the dominating mechanism due to the presence of major peaks of Safranin O on the IR spectra of Safranin O loaded biosorbent, indicating that the Safranin O was present in its unaltered form on the surface of the biosorbent.

Applicability of immobilized wood-rotting fungal biomass for biosorption of basic dye Alcian Blue.

In this study potential applicability of immobilised biomass of a wood-rotting dead macro-fungus Fomitopsis carnea are explored for the removal of the basic dye Alcian Blue. Effect of several parameters viz., temperature, pH and salt were studied in batch mode. In view of reutilization of the dye as well as the biosorbent, desorption/regeneration experiments were conducted. Desorption/regeneration studies could also be helpful in determining dye sorption mechanism. Studies indicate that the immobilized biosorbent could remove Alcian Blue efficiently. The experimental equilibrium data were modeled using the Langmuir equation. Dye uptake capacity of the biosorbent was observed to increase with rise in temperature and indicates chemisorption and/or ion exchange. The uptake was 11.1, 13.2, 16.4 and 24.2 mg/g at 10, 20, 30 and 40 degrees C respectively. Higher removal of dye was also observed at higher pH. However, increased salt concentration from 0 mmol/L to 100 mmol/L reduced from 89 to 85%. Desorption of dye could be possible up to 51% using 0.1 M hydrochloric/acetic acids and thus suggests that ion-exchange and chemisorption could be the possible dye sorption mechanism.