A Simple and Effective Bio-adsorbent Generated from the Stems of Momordica charantia Plant for the Simultaneous Removal of Lead and Cadmium Ions from Wastewater

Sulphuric acid generated activated carbon from the stems of Momordica charantia (MCSAC) was identified to adsorb lead(II) and cadmium(II) ions from water. Extraction conditions were optimized. At pH: 6, both the ions can be simultaneous removed by 2.0 mg/L of MCSAC after an equilibration period of 90 min at room temperate (30 ± 2 ºC). The sorption capacities were observed to be 21.0 mg/g for Pb2+ and 18.9 mg/g for Cd2+. MCSAC was characterized by conventional methods and also by surface morphology assessing techniques such as XRD, FTIR and FESEM. The sorption mechanism was investigated by evaluating thermodynamic parameters and by adopting various kinetic and isothermal models. High ΔH values of 29.399 KJ/mol for Pb2+ and 33.222 KJ/mol for Cd2, indicated that the mechanism of sorption is ion exchange and /or complex formation between Pb2+/Cd2+ ions and surface functional groups present in MCSAC. Further, high positive ΔS values imply the presence of disorder at solid-liquid interface, favouring the metal ions to overcome the surface barrier and get adsorbed. The negative ΔG values indicates the spontaneity of sorption process. Spent MCSAC can be regenerated and reused for three cycles. The procedure developed using MCSAC as sorbent was successfully applied to treat real effluents samples collected from several industrial effluents. The novelty of the present investigation is that a simple biosorbent is developed for the effective simultaneous removal of highly toxic Pb2+ and Cd2+ from contaminated water.

Effect of sulfate on sorption of Eu(III) by Na-montmorillonite

Smectite-rich natural clay is being evaluated as the backfill and buffer material in the Indian repository program for the nuclear high level waste disposal. In the natural clay, montmorillonite is one of the major mineral component governing the sorption behavior of various radionuclides. In the present work, influence of sulfate anion on sorption of Eu(III) by Na-montmorillonite has been investigated. The effect of pH and sulfate concentration on Eu(III) sorption by Na-montmorillonite was used to understand the mechanism of sorption process. The Eu(III) sorption by clay at varying pH was virtually pH independent at lower pH (<4), with ion exchange as the dominant mode for Eu(III) sorption. In the pH region of 4–6.5, sharp increase in sorption indicates surface complexation as predominant mechanism. At pH>6.5, the sorption attained a constant value. To deduce the mechanism of sorption of Eu(III) on Na-montmorillonite surface in presence of sulfate, ATR-FTIR spectroscopic investigations has been carried out which indicate the presence of sulfate bearing species on Na-montmorillonite surface. Using spectroscopic findings as a guide, the surface complexation modeling, in absence and presence of sulfate, was successfully carried out.

Application of Inorganic Fe(III)-Based Sorbent for Arsenic Sorption

The efficiency of iron oxy-hydrate application for cleaning aqueous media from arsenic has been studied. It is proposed to precipitate the active layer to a coarse-grained carrier to improve filterability. Metallurgical alumina and quartz sand are considered as carrier materials. Conditions for the synthesis of inorganic sorbent based on iron oxy-hydrate are established. The dependence of the sorbent capacity on the pH of the solution is determined. IR spectra of the sorbent before and after sorption of arsenic are given, and the mechanism of sorption of arsenic is proposed. The data on the capacity of the obtained sorbent modifications for the sorption of As (III) ions under static conditions are presented.

Adsorption of copper (II) ions from aqueous solution using bottom ash of expired drugs incineration

The use of bottom ash of expired drugs incineration for removal of Cu(II) ions from aqueous solution has been investigated. Analytical techniques have been employed to find characteristics of adsorbent materials. The removal of Cu(II) was conducted in batch system, and the effects of pH, adsorbent dosage, initial concentrations of copper ions, and contact time on adsorption efficiency were studied. Optimum adsorption was achieved at a pH 5 and equilibrium was established within 15 min of the process. The equilibrium adsorption data were analyzed using eight adsorption isotherm models: Langmuir, Freundlich, Temkin, Redlich–Peterson, Dubinin–Radushkevich, Toth, Harkin–Jura and Halsey isotherms. The energy value obtained by application of Dubinin–Radushkevich model was 2.593 kJ/mol indicating that physisorption was the dominant mechanism of sorption. The values of the correlation coefficient (R2) of the isotherms gave the best fit (>0.99) with the Langmuir, Toth, and Redlich–Peterson isotherms. The adsorption capacity (qm) from the Langmuir isotherm for Cu(II) was found as 13.335 mg/g. The equation constant n of Toth isotherm model is found to be close to 1 (0.945), confirming that the adsorbent studied presents homogeneous surface under conditions used. It is concluded that bottom ash of expired drugs incineration can be used as an effective adsorbent for removing Cu(II) from aqueous solution.