Removal of lead from aqueous solutions using three biosorbents of aquatic origin with the emphasis on the affective factors

The biosorptive potentials of three aquatics-based biosorbents, including shells of a bivalve mollusk and scales of two fish species for Pb removal from aqueous solutions were evaluated, for the first time. A Box–Behnken design with the response surface methodology was used to investigate the effects of the seven important variables (contact time, temperature, initial concentration, dosage, size, salinity and pH) on the sorption capacity of the sorbents. Among the seven studied factors, the effects of biosorbent dosage, initial concentration and pH were significant for all the response variables, while biosorbent size was not significant for any of the responses. The initial concentration was the most influential factor. The presence of Pb ions on the surfaces of the biosorbents after the adsorption was clearly confirmed by the SEM–EDX and XRF analyses. The maximum sorption capacities of the biosorbents were comparable to the literature and the descending order was as follows: scales of Rutilus kutum and Oncorhynchus mykiss and the shells of Cerastoderma glaucum. The isotherm studies revealed Langmuir model applicability for the Pb adsorption by R. kutum and O. mykiss scales, while Freundlich model was fitted to the adsorption C. glaucum shells.

Controllable Preparation of Cubic Zeolite A and Application of Langmuir Model in Carbon Dioxide Adsorption

A large amount of remaining fly ash has been piled up or landfilled, which not only a waste of land resources but also results in a series of environmental problems. Therefore, using fly ash to produce high value-added products is a win-win development orientation between human beings and nature. In this study, zeolite A is successfully synthesized using a hydrothermal method using fly ash. Additionally, it is at 1.0 mol·L−1 of the alkali concentration that the crystallinity of zeolite A reaches the maximum value, about 96.6%. FTIR research shows that the main secondary structural unit D4R vibration band of zeolite A appears at 555 cm−1. The results of the SEM study indicate the structure of zeolite A is cubic. The TEM results show that the crystal structure of the zeolite A belongs to the body-centered cubic structure. Meanwhile, the positively charged sodium ions cooperate with the silicon oxygen tetrahedron and the aluminum oxygen tetrahedron to form the zeolite A skeleton. Carbon dioxide adsorption equilibrium study shows that the maximum adsorption capacity of zeolite A of 46.5 mL·g−1 is significantly higher than the maximum adsorption capacity of commercial-grade zeolite 4A of 39.3 mL·g−1. In addition, the application of the Langmuir model in the adsorption of carbon dioxide by commercial-grade zeolite 4A and zeolite A is studied, which not only extends the application of zeolite A, but can be further extended to other zeolite materials as well. Meanwhile, the adsorption process belongs to the Langmuir model, which is a single layer adsorption on an ideal surface.

Elimination of Acid Red 88 by Waste Product from the Phosphate Industry: Batch Design and Regeneration

Waste regenerated after washing of rock phosphate and phosphogypsum has been proposed as removal agents of Acid Red 88 (AR 88)) from artificially contaminated solution. Natural phosphate (PN) was also studied for comparison. These materials were characterized beforehand, as is intended for the removal tests, by chemical analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis– differential thermal analysis, scanning electron microscopy, and N2 adsorption isotherms. The conducted experiments show that among the different materials, the PWR has the highest retention capacity of the dye (123.4 mg g−1) of AR-88. Upon calcinations, the removal capacities reduced by 60 to 70%. We take note also that a decrease in the amount of removed AR 88 dye occurs with an increase in pH. The kinetics data on the reaction between AR 88 and the materials are described well by a pseudo -second-order model. The Langmuir model is successfully applied to the experimental data of the removal of acid red 88. The removal process is exothermic.

Sorption of Uranium (VI) From Aqueous Solution Using Nanomagnetite Particles; Singly and Coated With Humic Acid

Magnetite nanoparticles (Fe3O4) and humic acid coated magnetite nanoparticles (Fe3O4/HA) were investigated for the removal of U(VI) from aqueous solution. Batch sorption experiments were studied as a function contact time, adsorbent mass, U(VI) concentration and pH. The sorption kinetic data follow the pseudo-second order while the isotherms are found to obey Langmuir model with maximum capacity (Qmax) of 230, 196 mg/g for Fe3O4 and Fe3O4/HA, respectively. The study reveals that humic acid decreases the sorption capacity due to the formation of a polyanionic organic coating and thus altering the surface properties of the particles and reduces the magnetite aggregation and stabilizes the magnetite suspension.

STUDI ISOTEM DAN KINETIKA ADSORPSI BAHAN ORGANIK ALAMI (BOA) PADA AIR GAMBUT TERHADAP KARBON AKTIF KAYU ULIN DENGAN SISTEM BATCH

Air gambut di Indonesia khususnya di Kalimantan Selatan sangat berlimpah dan memiliki potensi untuk dijadikan sebagai sumber air bersih. Keberadaan bahan organik yang tinggi di dalam air gambut membuat air gambut perlu dilakukan pengolahan terlebih dahulu. Salah satu pengolahan yang dapat dilakukan yaitu dengan proses adsorpsi. Adsorpsi suatu zat pada permukaan adsorben bergantung pada beberapa faktor dan memiliki pola isoterm dan kinetika tertentu. Penelitian ini bertujuan untuk menentukan model isoterm, dan model kinetika yang sesuai pada adsorpsi bahan organik alami (BOA) terhadap karbon aktif kayu ulin. Metode dalam penelitian ini menggunakan proses adsorpsi dengan adsorben karbon aktif kayu ulin. Model isoterm yang digunakan yaitu model Langmuir, model Freundlich, dan model Redlich-Peterson, sedangkan model kinetika yang digunakan ialah model Pseudo Orde Satu, Pseudo Orde Dua, dan Freundlich Modifikasi. Model isoterm Redlich-Peterson merupakan model yang sesuai untuk adsorpsi BOA air gambut terhadap karbon aktif kayu ulin dan model kinetika yang sesuai untuk adsorpsi BOA air gambut terhadap karbon aktif kayu ulin adalah model Pseudo Orde Dua.

Biosorption of Zn(II) from Seawater Solution by the Microalgal Biomass of Tetraselmis marina AC16-MESO

Biosorption refers to a physicochemical process where substances are removed from the solution by a biological material (live or dead) via adsorption processes governed by mechanisms such as surface complexation, ion exchange, and precipitation. This study aimed to evaluate the adsorption of Zn2+ in seawater using the microalgal biomass of Tetraselmis marina AC16-MESO “in vivo” and “not alive” at different concentrations of Zn2+ (0, 5, 10, and 20 mg L−1) at 72 h. Analysis was carried out by using the Langmuir isotherms and by evaluating the autofluorescence from microalgae. The maximum adsorption of Zn2+ by the Langmuir model using the Qmax parameter in the living microalgal biomass (Qmax = 0.03051 mg g−1) was more significant than the non-living microalgal biomass of T. marine AC16-MESO (Qmax = 0.02297 mg g−1). Furthermore, a decrease in fluorescence was detected in cells from T. marina AC16-MESO, in the following order: Zn2+ (0 < 20 < 5 < 10) mg L−1. Zn2+ was adsorbed quickly by living cells from T. marine AC16-MESO compared to the non-living microalgal biomass, with a decrease in photosystem II activities from 0 to 20 mg L−1 Zn2+ in living cells.

Sorption–Desorption Behavior of Doxycycline in Soil–Manure Systems Amended with Mesquite Wood Waste Biochar

Elevated levels of doxycycline (DC) have been detected in the environment due to its extensive utilization as a veterinary antibiotic. Sorption–desorption behavior of DC in soil affects its transport, transformation, and availability in the environment. Thus, sorption–desorption behavior of DC was explored in three soils (S1, S2, and S3) after manure application with and without mesquite wood-waste-derived biochar (BC) pyrolyzed at 600 °C. Sorption batch trials demonstrated the highest DC sorption in soil S1 as compared to S2 and S3, either alone or in combination with manure or manure + BC. Chemical sorption and pore diffusion were involved in DC sorption, as indicated by the kinetic models. Soil S1 with manure + BC exhibited the highest Langmuir model predicted sorption capacity (18.930 mg g−1) compared with the other two soils. DC sorption capacity of soils was increased by 5.0–6.5-fold with the addition of manure, and 10–13-fold with BC application in a soil–manure system. In desorption trials, manure application resulted in 67%, 40%, and 41% increment in DC desorption in soil S1, S2, and S3, respectively, compared to the respective soils without manure application. In contrast, BC application reduced DC desorption by 73%, 66%, and 65%, in S1, S2, and S3, respectively, compared to the soils without any amendment. The highest DC sorption after BC application could be due to H bonding, π–π EDA interactions, and diffusion into the pores of BC. Hence, mesquite wood-waste-derived BC can effectively be used to enhance DC retention in contaminated soil to ensure a sustainable ecosystem.

Physical properties of mesoporous scoria and pumice volcanic rocks

In this study, the chemical composition, crystal structure, texture properties, and thermal properties of five powdered samples of scoria and pumice volcanic rock from different Harrats were investigated. It was observed that volcanic rocks show variations in chemical compositions, crystal structure, texture, and thermal properties. All samples comprised SiO2, Al2O3, CaO, and Fe2O3 as the major elements and contained both amorphous and crystalline phases. Textural parameters such as surface area and porosity were determined using various calculation models. The surface area of scoria samples was between 0.85 and 1.71 m2/g (Brunauer–Emmett–Teller and Single point model), 0.293-1.028 m2/g (Barrett–Joyner–Halenda model), and 1.02- 2.35 m2/g (Langmuir model). While for pumice, the calculated values of the surface area were 1.67 m2/g (Brunauer–Emmett–Teller and Single point model), 0.763 m2/g (Barrett–Joyner–Halenda model), and 2.24 m2/g (Langmuir model). The adsorption-desorption isotherm curves reveal that the scoria and pumice particles under study have mesoporous sizes between 7.89 and 9.81 nm, respectively. The differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results of scoria and pumice samples illustrate a thermally stable material at high temperatures. TGA results show a weight gain by about 1.0% has been observed in the scoria samples in the region beyond 600 ℃ that may indicate a probable oxidation phenomenon with change color. While the DSC results of the red scoria and pumice did not show any recrystallization or oxidation, but only showed a small loss weight in the TGA result. The diversity in molecular composition, texture, and structure of scoria and pumice volcanic rock samples provide for promising natural stable mesopore materials that can be used in various mesopore technologies or applications such as solar cells.

Phosphate and Ammonium Removal from Wastewaters Using Natural-Based Innovative Bentonites Impacting on Resource Recovery and Circular Economy

The research objective of the study is the estimation of a novel low-cost composite material f-MB (Fe-modified bentonite) as a P and N adsorbent from wastewaters. Τhe present study aimed at examining the phosphate and ammonium removal efficiency from different types of wastewater using f-MB, by conducting bench-scale batch experiments to investigate its equilibrium characteristics and kinetics. The SEM analysis revealed that the platelets of bentonite in f-MB do not form normal bentonite sheets, but they have been restructured in a more compact formation with a great porosity. Regarding the sorption efficiencies (Qm), the maximum phosphate sorption efficiencies (Qm) calculated using the Langmuir model were 24.54, 25.09, 26.13, 24.28, and 23.21 mg/g, respectively, for a pH range of 5 to 9. In addition, the maximum NH4+-N adsorption capacities (Qm) calculated from the Langmuir model were 131.8, 145.7, 168.5, 156.7, and 159.6 mg/g, respectively, for a pH range from 5 to 9. Another important finding of this study is that f-MB can recover P from treated wastewater impacting on resource recovery and circular economy (CE). The modified clay f-MB performed the phosphate and ammonium recovery rates of 80% and 78.5%, respectively. Finally, f-MB can slowly release the largest proportion of phosphate and ammonium ions for a long time, thus extending the application of the f-MB material as a slow-release fertilizer and soil improver.

Amino-Thiol Bifunctional Polysilsesquioxane/Carbon Nanotubes Magnetic Composites as Adsorbents for Hg(II) Removal

Amino-thiol bifunctional polysilsesquioxane/carbon nanotubes (PSQ/CNTs) magnetic composites were prepared by sol-gel method with two types of functional siloxanes coating on carboxyl CNTs simultaneously. The composites were served as efficient adsorbents for removing Hg(II) in aqueous solution and the adsorption properties were investigated systematically. The optimal pH of bifunctional composites for Hg(II) removal is at pH 4.5. The thermodynamic fitting curves are more consistent with the Langmuir model and the adsorption capacities of the bifunctional composites for Hg(II) varied from 1.63 to 1.94 mmol g−1 at 25°C according to the Langmuir model. The kinetics curves are more fitted to the pseudo-second-order model and the composites could selectively adsorb Hg(II) in a series of binary metal ions solution. The elution regeneration tests showed that the adsorption rate could still reach 78% after repeat cycle three times. It is expected that the bifunctional PSQ/CNTs magnetic composites can be potentially applied to remove low concentration Hg(II) from waste water.