Irreversible sorption of Pb(II) from aqueous solution on breadfruit peel to mitigate environmental pollution problems.

Development of efficient and environmentally friendly methods to remove toxic pollutants from aqueous systems is a requirement to mitigate ever increasing environmental pollution problems. In this context, Artocarpus altilis (breadfruit) peel (BP), a waste material, can be used as a low-cost adsorbent for the removal of Pb(II) ions from synthetic pollutant solutions. The extent of removal of Pb(II), under optimized conditions in experimental batch experiments, is determined to be 82.0%, which is decreased in highly ionic environments, partly due to competition for a limited number of active adsorption sites, indicating the necessity of optimizing experimental parameters for the most efficient removal. Regression analysis and error function values evaluated for isotherm models associated with different adsorption mechanisms, namely Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson and Sips, indicate that the best fitted model is the Sips followed by the Langmuir model with adsorption capacities (qmax) of 78.50 mg g-1 and 85.42 mg g-1, respectively. Thermodynamics arguments support the spontaneous and exothermic behavior of the Pb(II)-BP adsorption system, while adsorption kinetics of the system provides evidence for the applicability of the pseudo second order model with a rate constant of 0.504 g mg-1 min-1.

Use pattern of pesticides and their predicted mobility into shallow groundwater and surface water bodies of paddy lands in Mahaweli river basin in Sri Lanka.

Pesticides applied on agricultural lands reach groundwater by leaching, and move to offsite water bodies by direct runoff, erosion and spray drift. Therefore, an assessment of the mobility of pesticides in water resources is important to safeguard such resources. Mobility of pesticides on agricultural lands of Mahaweli river basin in Sri Lanka has not been reported to date. In this context, the mobility potential of 32 pesticides on surface water and groundwater was assessed by widely used pesticide risk indicators, such as Attenuation Factor (AF) index and the Pesticide Impact Rating Index (PIRI) with some modifications. Four surface water bodies having greater than 20% land use of the catchment under agriculture, and shallow groundwater table at 3.0 m depth were selected for the risk assessment. According to AF, carbofuran, quinclorac and thiamethoxam are three most leachable pesticides having AF values 1.44 × 10-2, 1.87 × 10-3 and 5.70 × 10-4, respectively. Using PIRI, offsite movement of pesticides by direct runoff was found to be greater than with the erosion of soil particles for the study area. Carbofuran and quinclorac are most mobile pesticides by direct runoff with runoff fractions of 0.01 and 0.08, respectively, at the studied area. Thiamethoxam and novaluron are the most mobile pesticides by erosion with erosion factions of 1.02 × 10-4 and 1.05 × 10-4, respectively. Expected pesticide residue levels in both surface and groundwater were predicted to remain below the USEPA health advisory levels, except for carbofuran, indicating that pesticide pollution is unlikely to exceed the available health guidelines in the Mahaweli river basin in Sri Lanka.

Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g(-1), that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment.

Biosorption of cadmium(II) and copper(II) ions from aqueous solution by core of Artocarpus odoratissimus.

PURPOSE: This research is on the evaluation of biosorption capability of the core of Artocarpus odoratissimus (Tarap), grown in Brunei Darussalam, towards Cd(II) and Cu(II) ions present in synthetic solutions, and to characterize the surface of Tarap particles. METHODS: Thermogravimetric analysis and surface titrations were conducted to characterize the surface of dried Tarap core particles. Atomic absorption spectroscopic measurements were conducted to determine the extent of removal of Cd(II) and Cu(II) under different experimental conditions. RESULTS: Mass reductions associated with many exothermic reaction peaks were observed beyond 200°C up to 650°C indicating the combustion of organic matter in Tarap. Dried particles of core of Tarap bear a negative surface charge promoting strong interaction towards positively charged ions, such as Cu(II) and Cd(II). Biosorption of the two metal ions on Tarap, which is relatively high beyond pH = 4, occurs within a short period of exposure time. The extent of biosorption is enhanced by acid treatment of the biosorbent, and further it does not significantly depend on the presence of nonreacting ions up to an ionic strength of 2.0 M. CONCLUSION: Strong attraction between each metal ion and the biosorbent is attributed to the negative surface charge on the biosorbent within a broad pH range. Acid treatment of the biosorbent improves sorption characteristics, suggesting that ion exchange plays an important role in the metal ion-biosorbent interaction process.

Investigation of kinetics of Cr(VI)-fired brick clay interaction.

Fired brick clay is an excellent sorbent for the removal of heavy metal ions from waste water, owing to the availability of pores and interlayer spacing. Consequently, heat treatment of brick clay significantly affects the extent of interaction between the brick clay sorbent and adsorbates. The interaction between Cr(VI), available as Cr(2)O(7)(2-), and brick clay particles fired at temperatures between 200 °C and 600 °C follows pseudo second order kinetics, and the method of initial rates leads to the estimation of the average rate of the interaction process. Kinetics modeling suggests that the mass transfer of the interaction be mainly controlled by time-dependent intraparticle diffusion, as well as immobilization of Cr(VI) species within interlayer structure of the brick clay matrix and interparticle diffusion, both of which are time-independent.

Interaction of Cr(VI) species with thermally treated brick clay.

PURPOSE: The purpose of this research is to investigate the interaction of Cr(VI) species, present as Cr2O7²â», at ambient temperature with brick clay pre-fired at different temperatures. METHODS: A multi-technique approach was used for this investigation. Experiments such as surface titrations, Langmuir and Freundlich adsorption isotherms, mass-firing temperature investigation, scanning electron microscopy, Fourier transform infrared spectra, X-ray fluorescence spectra, and X-ray diffraction were conducted in this investigation. RESULTS: Fired brick clay, which bears a negative charge according to surface titration measurements, shows affinity towards Cr(VI) species despite the negative charge of the source of Cr(VI). The Cr(VI)-brick clay heterogeneous system, which shows the strongest interaction with brick clay fired at 200 °C, obeys both the Langmuir and the Freundlich adsorption isotherms with high regression coefficients. Investigation on surface charge, constituents of brick clay, acid treatment of clay particles, and the effect of firing temperature suggests that the reduction of Cr(VI) to Cr(III) by reducing agents present in brick clay makes a significant contribution for adsorption of chromium species followed by subsequent removal. Scanning electron microscopic images support the adsorption of chromium species, and further, many metal ions are released as a result of Cr(VI)-brick clay interaction according to X-ray fluorescence studies. CONCLUSION: It is concluded that fired brick clay shows strong adsorption capacity on Cr(VI), having the maximum interaction with brick clay fired at 200 °C. It is proposed that this methodology be extended for treatment of effluents containing Cr(VI) species.