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The powdered biomass of paddle cactus (Tacinga palmadora), a rustic plant of great occurrence in the driest regions of Brazil, was evaluated as a low-cost adsorbent to treat textile effluents containing crystal violet (CV) dye. The powdered paddle cactus (PPC) was mainly composed by lignin and holocellulose, as well as, a variety of functional groups. Best results for CV adsorption were found using an adsorbent dosage of 0.5 g L−1 at solution pH equivalent to 10.0. Fast adsorption kinetics was verified, being the equilibrium reached within 100 min, and the curves were well modeled by the pseudo-first-order model. The isotherms were well-represented by the Langmuir model. The maximum adsorption capacity was 228.74 mg g−1 at 328 K. The estimated thermodynamics parameters were ΔG0T = 328K of –9.08 kJ mol−1, ΔH0 of 12.44 kJ mol−1, and ΔS0 of 0.065 kJ mol−1 K−1. In addition, PPC was able to treat a simulated textile effluent containing organic and inorganic compounds, reaching 93% of color removal efficiency. These findings show that powdered paddle cactus can be applied as potential low-cost adsorbent to treat textile effluents containing CV. [ABSTRACT FROM AUTHOR]

A magnetic geopolymer was prepared from the silica and metakaolin under presence of zero–valent iron (ZVI). The magnetic geopolymer was characterized by Fourier–Transform Infrared spectroscopy, X-ray diffraction, N2 adsorption/desorption isotherms, scanning electron microscopy, and vibrating sample magnetometer. The geopolymer was employed as adsorbent of Acid Red 97 dye. The results showed that the magnetic geopolymer have mesoporous structure and sufficient magnetization to be removed by a magnetic field from aqueous solution. Both the pseudo–first and pseudo–second order models satisfactorily described the adsorption kinetics, and the isotherms were properly adjusted by the Henry's model. High adsorptive capacity of dye (1814 mg g−1) was obtained, and the geopolymer can be used for five times with the same initial adsorption capacity. An efficient adsorbent was developed from low cost materials. This adsorbent presented extremely high adsorption capacity and can be easily separated from the treated liquid effluent. [ABSTRACT FROM AUTHOR]

In this work, Moringa oleifera seed husk (MOSH) and Moringa oleifera seed pulp (MOSP) were converted via a green route into efficient biosorbents for biosorption of Acid Blue 9 (AB9) synthetic dye from the wastewater. The textural properties, morphologies, and structures of both biosorbents were analyzed using Fourier infrared spectroscopy (FTIR), N 2 adsorption/desorption isotherms, pH of point-zero-charge (pH PZC), and scanning electron microscope (SEM). The characterization results showed that the biosorbents have heterogeneous surfaces with a diversity of functional groups. The experimental data of biosorption kinetics were best described by the nonlinear Avrami fractional. The isothermal empirical data were supported by the nonlinear Liu equation, and the maximum biosorption capacities of MOSH and MOSP at 55 °C for AB9 synthetic dye are 329.5 mg g–1 and 694.2 mg g–1, respectively. The evaluation of thermodynamic parameters showed that the biosorption processes of both biosorbents were spontaneous, endothermic, and occurred by physisorption. The availability, low-cost, high adsorption capacity, and fast adsorption kinetics of MOSH and MOSP make them alternative, promising, and attractive green biosorbents for removal AB9 synthetic dye from aqueous solutions. [Display omitted] • Green preparation of highly efficient biosorbents. • Moringa oleifera seed (husk and pulp) were utilized as biosorbents. • Functional groups have a notable influence on the adsorption process. • MOSH and MOSP present adsorption capacities of 329.5 and 694.2 mg g−1. • Biosorption process are described by Liu isothermal and Avrami kinetic models. [ABSTRACT FROM AUTHOR]