Adsorption mechanism of chromium(III) using biosorbents of Jatropha curcas L

The removal of Cr³⁺ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated. Adsorption tests were performed in batch systems for evaluating the influence of the solution's pH, adsorbent mass, contact time, initial Cr³⁺ concentrations, and solution temperature during the adsorption process. Kinetic, adsorption isotherm, and thermodynamic studies were performed to investigate the mechanisms that control adsorption. Ideal conditions for the adsorption process included pH of the solution of 5.5 and 8 g L^-1 adsorbent mass, within 60 min time contact between adsorbent and adsorbate. Maximum adsorption capacities by Langmuir model for rind, endosperm, and endosperm + episperm of the J. curcas were, respectively, 22.11, 18.20, and 22.88 mg g^-1, with the occurrence of chemosorption in mono and multilayers. Results show that the biosorbents obtained from J. curcas have a high potential to recuperate Cr³⁺ from contaminated water sources.

Adsorption of Cu (II) and Zn (II) from Water by Jatropha curcas L. as Biosorbent

The objective of this work was to evaluate the removal of Cu2+ and Zn2+ in water by means of the adsorption process using three biosorbents derived from jatropha biomass (bark, endosperm and endosperm + seed coat). The experiments were performed in batch and evaluated the effect of solution pH, adsorbent mass, contact time, different initial concentrations of the metals Cu2+ and Zn2+, and the temperature of the solution during the adsorptive process. By kinetics, the adsorption isotherms and thermodynamics the mechanisms that control the adsorptive process were evaluated. The optimal conditions for the realization of the adsorptive process for both metals were: solution pH of 5.0 and 8 g L-1 of adsorbent mass per volume of solution, with a contact time between adsorbent and adsorbate of 60 min. According to the Langmuir model, the maximum adsorption capacities for the bark, endosperm and endosperm + seed coat of Jatropha were, respectively, for Cu2+ 11.541, 20.475 and 22.910 mg g-1, and for Zn2+ 14.852; 15.888 and 14.674 mg g-1, with the predominance of chemisorption in monolayer. The three biosorbents derived from the biomass of Jatropha have potential for the remediation of water contaminated with Cu2+ and Zn2+.

Studies of Pb2+ adsorption by Moringa oleifera Lam. seeds from an aqueous medium in a batch system

The efficiency of Moringa (Moringa oleifera Lam.) seeds for removing lead ions (Pb(2+)) from water was evaluated. Parameters such as solution pH, adsorbent mass, contact time between solution and adsorbent, isotherms, thermodynamic, kinetics, and desorption were evaluated. The maximum adsorption capacity of the biosorbent was found to be 12.24 mg g(-1). In order to verify the effectiveness of this material, comparative studies were performed with activated carbon under the same optimal conditions for the construction of isotherms and the desorption process. Average desorption rate values led to the assumption that a strong interaction took place between the adsorbents and the metal ions. Thus, it has been concluded that the biosorbent studied herein can be considered very effective and feasible for remediating Pb(2+)-contaminated solutions, since this material is itself an untreated and low-cost byproduct.

Availability of heavy metals (Cd, Pb, And Cr) in agriculture from commercial fertilizers

The purpose of this study was to investigate the availability of the heavy metals cadmium (Cd), lead (Pb), and chromium (Cr) to soil and maize plants fertilized with different sources and doses of zinc (Zn) in a Rhodic Eutrudox soil. For that purpose, concentrations of Cd, Pb, and Cr were evaluated in leaf tissue and grains of maize plants and in 0-20 and 20-40 cm soil layers after fertilization with four doses of Zn from eight different sources of fertilizer. There was no accumulation of Cd, Pb, and Cr in maize grain and Cd and Cr in leaf tissue of the plants; nevertheless, there was accumulation of Pb in leaf tissue, showing its availability throughout different sources of Zn and consequent uptake by plants. Regarding the soil, it was observed that fertilizer from the different sources made Cd, Pb, and Cr available at increasing amounts proportional to increased Zn doses. Under experimental conditions, fertilization with Zn increased concentrations of heavy metals Cd, Pb and Cr in soil, further highlighting the importance of conducting more studies related to the application of mineral fertilizers for micronutrient supply and the availability of heavy metals.