Pritee Goyal

Saraca indica leaf powder for decontamination of Pb: removal, recovery, adsorbent characterization and equilibrium modeling

The present study explores the effectiveness of Saraca indica leaf powder, a surplus low value agricultural waste, in removing Pb ions from aqueous solution. The influence of pH, biomass dosage, contact time, particle size and metal concentration on the removal process were investigated. Batch studies indicated that maximum biosorption capacity for Pb was 95.37% at the pH 6.5. The sorption process followed the first order rate kinetics. The adsorption equilibrium data fitted best to both Langmuir and Freundlich isotherms. Morphological changes observed in scanning electron micrographs of untreated and metal treated biomass confirmed the phenomenon of biosorption. Fourier transform infrared spectroscopy of native and exhausted leaf powder confirmed lead biomass interactions responsible for sorption. Acid regeneration was tried for several cycles with a view to recover the sorbed metal ion and also to restore the sorbent to its original state. The findings showed that Saraca indica leaf powder can easily be envisaged as a new, vibrant, low cost biosorbent for metal clean up operations.

Characterization of novel Zea mays based biomaterial designed for toxic metals biosorption.

Structural modifications onto Zea mays Cob powder, ZMCP lead to the formation of novel biomaterial with increased sorption efficiency and environmental stability for the abatement of Pb (II), Cd (II), Ni (II) and Cr (III) in single as well as multi-metal ion solutions. Synthetic strategy for strengthening the functional groups, COO(-) responsible for binding of metal species has been applied using acetylation, succination and graft co-polymerization processes. The resultant novel biomaterial exhibits enhancement in sorption efficiency from 2 to 15% and stability in terms of regeneration cycles from 3 to 5, evidence to support biomaterial designed has been provided on the basis of SEM, FTIR and TGA. The findings open up new avenues in the modern Green Technology of water treatment using biosorbent-possessing potential for commercialization.

Biosorption: Application Strategies

Over the past few years, intensifying research into metal biosorption elucidated the principles of this effective metal removal phenomenon. Biosorption can be cost-effective, particularly in environmental applications where low cost of the metal removal process is most desirable. Some efficient natural biosorbents have been identified that require little modification in their preparation. It is particularly in ecological aspects where biosorption can make a difference due to its anticipated low cost. The application aspect is what makes the research and development work in this novel area exciting and worthwhile. While the biosorption process could be used even with a relatively low degree of understanding of its metal-binding mechanisms, better understanding will make for its more effective and optimized applications. If the biosorption processes were to be used as an alternative in the wastewater treatment scheme, the regeneration of the biosorbent may be crucially important for keeping the process cost down and to open the possibility of recovering the metals extracted from liquid phase. For this process it is desirable to desorb the sorbed metals and to regenerate the biosorbent material for another cycle of application.

Biosorption of trivalent and hexavalent chromium from aqueous systems using shelled Moringa oleifera seeds

Abstract The present study explores the sorption properties of shelled Moringa oleifera seeds (SMOS) for removal of two environmentally important oxidation states of chromium (trivalent and hexavalent) from an aqueous system on the laboratory scale. Sorption studies reveal the optimum conditions for the removal of 81.02%; Cr (III) and 88.15% Cr (VI) as follows: biomass dosage (4.0 g), metal concentration [25mg/L for Cr (III); 50mg/L for Cr (VI)], contact time (40 minutes) at pH 6.5 and 2.5 respectively. The adsorption data were found to fit well both the Freundlich and Langmuir isotherms. Characterization of the seed powder by FTIR showed the clear presence of amino acid moieties having both positively charged amino and negatively charged carboxylic groups and confirmed that biosorption involves amino acid-chromium interactions. SEM studies of native and exhausted [Cr(III) and Cr(VI)] treated SMOS revealed large spherical clusters having a pore area of 8.66 µm2 in the case of native SMOS while dense agglomerated etched dendrite type morphology have a pore area of 0.80 µm2 in Cr (III) and 0.78 µm2 in Cr (VI) treated SMOS The spent biosorbent was regenerated and found to be effectively reusable for four cycles.

Sorption Isotherms and Kinetics

The distribution of metal ions between the biosorbent and the metal solution, when the system is at equilibrium, is of paramount importance in determining the maximum adsorption capacity of the biosorbent toward the metal ions. The adsorption data are to be analyzed in the light of various isotherm models like Freundlich and Langmuir adsorption models. The Freundlich isotherm model proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between adsorbed molecules. The Langmuir isotherm model suggests that uptake occurs on a homogenous surface by monolayer sorption. In addition, the model assumes uniform energies of adsorption onto the surface and no transmigration of the adsorbate.

Hyperaccumulation: A Phytoremedial Approach

The prime requisite of agriculture is soil which serves as a reservoir of nutrients and water for the crops. Unfortunately, all the soil available on this planet is not arable, fertile, and it remains agriculturally unproductive. Land is mainly contaminated with heavy metals like Zn, Pb, Cr, Ni, and Cd. Metal-rich mine tailings, metal smelting, electroplating, gas exhausts, fuel production, downwash from power lines, intensive agriculture, and sludge dumping are the most important human activities that contaminate soils with large quantities of toxic metals. Metals are non-biodegradable and have long biological half-life. Remediation of soil and water metals has been found to be a difficult and expensive goal. The remediation of heavy metal-contaminated soils can be achieved through various physical and chemical conventional remediation measures. Due to ever-growing number of toxic metal-contaminated sites, the commonly used methods dealing with heavy metal pollution are either extremely costly processes or simple isolation of the contaminated sites. The remediation of large volumes of contaminated sites by conventional technologies has been proved to be very expensive. It has been estimated that the cost of conventional remediation of heavy metal-contaminated sites in the USA alone would exceed

Detoxification of Metals – Biochelation

7 billion.

Heavy Metals: Environmental Threat

Several efforts have been made to detoxify the effect of metals once they are administered in the human body. Chelation is considered the best method used so far. Medicinal treatment of acute and chronic metal toxicity is provided by chelating agents. Chelation is one of the chemical functions that take place in the bodies of almost all living organisms. It is a process by which plants and animals utilize inorganic metals. Chlorophyll, the green matter of plants, is a chelate of magnesium. Hemoglobin, cytochrome C, catalase, and peroxidase are chelators of iron. A host of other metallo-enzymes could be used as examples involving chemical processes. Many of the successful drugs used in the treatment of disease are dependent on chelation processes for their effective therapeutic properties. Chelating agents are organic compounds capable of linking together metal ions to form complex ring-like structure called chelates. Chelate is derived from a Greek word meaning the claws of a lobster and somehow the chelators act in this way. Chelators form complex with the respective (toxic) ion. These complexes reveal a lower toxicity and are more easily eliminated from the body. This chapter focuses on the chemistry of these chelating agents and their pharmacological and toxicological properties. The beneficial and adverse effects including their limitations are briefly mentioned along with the recent developments to ameliorate the problems.

Designing of Experiments

Heavy metals are important among the toxic pollutants encountered in various ecosystems of the environment. The dissolved metals (particularly heavy metals) escaping into the environment pose a serious health hazard. These metals have been classified as priority pollutants by the US Environmental Protection Agency. Heavy metal pollution in the aquatic system has become a serious threat today and of great environmental concern as they are non-biodegradable and thus persistent. They accumulate in living tissues throughout the food chain which has humans at its top, multiplying the danger. Thus, it is necessary to control presence of heavy metals in the environment (Fig. 1).

Metal Decontamination: Techniques Used So Far

To design a good experiment several steps must be taken to ensure the results are as scientific as possible. Once the objective of the experiment has be determined, scientists must identify all the variables or factors which will affect the experiment. Scientists must then identify the different ways tests can be conducted to determine the outcome of the experiment. Now the experiment can begin. First a hypothesis identifies a variable will affect the outcome of the experiment and includes a prediction as to what that outcome will be. The variable selected is called the independent variable since it is the one selected and controlled by the experimenters. The effect measured will be the dependent variable since its outcome depends on the independent variable.