Maximum Adsorption Capacity Values Research Articles

Kinetic and Equilibrium Function and Switchable Catalytic Activity of Some Thermo-Responsive Hydrogel Metal Absorbents Based on Modified PNIPAM

Synthesis and identification of some thermo-responsive hydrogel metal absorbents based on Schiff base modified PNIPAM is described. PNIPAM hydrogel is produced through conventional free-radical polymerization method. The hydrogel is amino modified with different amines and then treated with various aldehydes to make polymeric Schiff-bases supposing to utilize as an absorbent for Cu salt. Characterization of the as-prepared hydrogels was performed properly and confirmed the corresponding structures. Kinetic and equilibrium function of the absorbents and the effect of distinct variables like pH, adsorbent amount and contact time in the absorption process are investigated in detail. Kinetic and adsorption isotherm data agreed with pseudo-second order model and Langmuir isotherm, respectively. The maximum value of adsorption capacity of the prepared adsorbent was around 8550 mg g−1. In addition, the corresponding switchable catalytic activity using one of the thermo-responsive hydrogel metal absorbents in the reduction of 4-nitro phenol to 4-amino phenol in the role of model reaction is examined.

Isothermal adsorption characteristics of various phases of CO2 and CH4 in different rank coals

ABSTRACT Using the remaining coal seams of closed coal mines for CO2 geological storage can effectively slow down the greenhouse effect and realize the redevelopment and utilization of closed coal mines. The burial depth of coal seams in closed coal mines in China covers an extensive range, and CO2 and CH4 could exist in various phases in the coal. The existing experimental objects for CO2 adsorption in coal are mainly associated with the supercritical and gaseous phases, and a research gap comparison between the CO2 adsorption characteristics in the liquid phase and those of other phases is very obvious. Herein, the isotherm adsorption experiments of CO2 and CH4 in different phases on different rank coal samples are methodically conducted in the pressure range of 0-12MPa. The experimental results indicate that the excess adsorption capacity of gaseous CO2 and CH4 (gas pressure <4MPa) rapidly raises with the growth of the adsorption pressure; however, a significant difference for the case of the medium- and high-pressure stage (>4MPa) is detectable. With the growth of the adsorption pressure, the excess adsorption capacity of the supercritical CH4 gradually reaches the maximum value and then remains stable, where the maximum experimental value is 1.009 mmol/g. While the excess adsorption capacity of CO2 near the critical pressure of liquid and supercritical state rapidly reduces and then tends to be stable. The maximum adsorption capacity is capable of touching 2.096 mmol/g, which is stable around 0.5 mmol/g. The analysis indicates that the change in the excess adsorption amount of CO2 near the critical pressure corresponds to the change in its density. The absolute adsorption capacity of CO2 and CH4 monotonically grows in the pressure range of 0-12MPa, and the absolute adsorption capacity of the same coal sample follows the following order: liquid CO2 > supercritical CO2 > CH4. The maximum adsorption capacity values for these substances in order are 2.493, 2.345, and 1.296 mmol/g. With the growth of the coal rank, the Gibbs free energy, specific surface area, and adsorption capacity of the understudied coal samples exhibit a U-shape relationship as a function of their coal ranks.

Efficient removal of congo red dye using activated lychee peel biochar supported Ca-Cr layered double hydroxide

Congo red is a known carcinogenic and mutagenic dye, so its presence in bodies of water is dangerous. The present work aims to synthesize and characterize a layered double hydroxide (LDH)-biochar composite and evaluate its application in the adsorption of Congo red dye (CR). CaCr/LDH was anchored over lychee activated biochar through coprecipitation. The composite was characterized using scanning electronic mapping (SEM), energy-dispersive spectrometer SEM (EDS-SEM), Fourier transform infrared (FT-IR), X-ray powder diffractometry (XRD) and Brunauer-Emmet-Teller (BET). The effect of pH, adsorption kinetics, isotherms, ionic strength, and thermodynamic parameters were evaluated. The pH results show a stable adsorption capacity in a useful range of pH (pH 4–9). Adsorption kinetics fitted the Elovich model, suggesting a heterogeneous system. The maximum adsorption capacity value (qe) calculated was achieved by applying the Sips model, with 631.1 mg g−1 at 50 °C. Ionic strength experiments show that the capacity increased with increasing NaCl concentration, which is desirable for real use as other ions are commonly present in dye wastewater. π-π interactions and hydrogen bonding seems to be involved in the adsorption mechanisms. CaCr-LDH/lychee biochar has better structure stability over several adsorption–desorption cycles with anionic exchange regeneration (in comparison with thermal regeneration), wide operational pH and high adsorption capacity. Therefore, this new composite presents a very good potential for the adsorption of dye from waste- or ground- water.

3D graphene sponge biomass-derived with high surface area applied as adsorbent for nitrophenols

The present work used wood sawdust as a carbon precursor to produce 3D graphene sponge material, a carbon material with an added value, successfully used as an adsorbent for removing o-nitrophenol and p-nitrophenol from aqueous effluents. The resulting material’s structural, morphological, textural, and chemical characteristics (WS-Graphene) were evaluated. Textural analysis revealed a high surface area (∼3000 m2g−1) and high total pore volume (1.38 cm3 g−1). Raman, infrared and X-ray diffraction techniques evidenced the presence of a few layers of graphene, with some fraction of defects. Transmission electron microscopy confirmed the presence of a 3D-packed structure for the graphene. These WS-Graphene characteristics favored its application as an adsorbent for removing o-nitrophenol and p-nitrophenol pollutants. The adsorption process of both nitrophenols was extremely rapid and reached the equilibrium time in less than 5 min when the concentration of both adsorbates was fixed at 700 mg L−1. Furthermore, the maximum adsorption capacity (Qmax) values were 1842 mg g−1 (o-nitrophenol) and 879.6 mg g−1 (p-nitrophenol) at 30 °C. These results confirm that the WS-Graphene adsorbent acts as a 3D sponge. Langmuir’s isothermal was the best-fitted model for both nitrophenols in aqueous solution. The o-nitrophenol adsorption onto WS-Graphene might follow pseudo-second-order as well as general-order, while the adsorption of p-nitrophenol might follow only the general-order model. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The WS-Graphene adsorbent presents a high percentage (∼97 %) of removing the mixture of pollutants in effluents, showing an excellent adsorption capacity and making it a potential material to remove industrial wastewater.

Highly adsorptive removal of palladium and platinum ions from wastewater using novel ethylenediamine-glutaraldehyde-grafted metal organic framework

Herein, a metal–organic framework (MIL-101(Cr)) was synthesized and functionalized with ethylenediamine-glutaraldehyde (ED-GA for removal of palladium (Pd2+) and platinum (Pt4+) from wastewater. The chemical structure, surface properties, morphology, and adsorption energy of the prepared materials, MIL-101(Cr) and MIL-101(Cr)/ED-GA were analyzed using several analytical techniques and density functional theory (DFT). The prepared MIL-101(Cr)/ED-GA was efficient in removing Pd2+ and Pt4+ from aqueous solution with the percentage removal reaching 95% for Pd2+ and 85% for Pt4+. Furthermore, the adsorption data demonstrated a good fit to the Langmuir isotherm model and gave the maximum adsorption capacity values of 416.17 mg g−1 for Pt4+ and and 322.6 mg g−1 for Pd2+ ions. Kinetics data obeyed a pseudo-second-order model and revealed the rapid adsorption of Pd2+ and Pt4+ ions by MIL-101(Cr)/ED-GA which reached equilibrium within 10 and 40 min, respectively. Lastly, DFT studies revealed that the adsorption of Pd2+ ions by the composite forms a more thermodynamically stable compound than adsorption of Pt4+, suggesting that the material easily interacts with Pd and high selectivity is thus expected. This was indeed confirmed by experimental selectivity test results. Owing to their high affinity for PGMs, N atoms depicted large adsorption energy values compared to other adsorption sites. The MIL-101(Cr)/ED-GA could act as an efficient and cost effective adsorbent for removal of platinum group metals from wastewater.

Synthesis of Xanthan Gum Anchored α-Fe2O3 Bionanocomposite Material for Remediation of Pb (II) Contaminated Aquatic System.

Increases in community and industrial activities have led to disturbances of the environmental balance and the contamination of water systems through the introduction of organic and inorganic pollutants. Among the various inorganic pollutants, Pb (II) is one of the heavy metals possessing non-biodegradable and the most toxic characteristics towards human health and the environment. The present study is focussed on the synthesis of efficient and eco-friendly adsorbent material that can remove Pb (II) from wastewater. A green functional nanocomposite material based on the immobilization of α-Fe2O3 nanoparticles with xanthan gum (XG) biopolymer has been synthesized in this study to be applied as an adsorbent (XGFO) for sequestration of Pb (II). Spectroscopic techniques such as scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet visible (UV-Vis) and X-ray photoelectron spectroscopy (XPS) were adopted for characterizing the solid powder material. The synthesized material was found to be rich in key functional groups such as -COOH and -OH playing important roles in binding the adsorbate particles through ligand-to-metal charge transfer (LMCT). Based on the preliminary results, adsorption experiments were conducted, and the data obtained were applied to four different adsorption isotherm models, viz the Langmuir, Temkin, Freundlich and D-R models. Based on the high values of R2 and low values of χ2, the Langmuir isotherm model was found to be the best model for simulation of data for Pb (II) adsorption by XGFO. The value of maximum monolayer adsorption capacity (Qm) was found to be 117.45 mg g-1 at 303 K, 126.23 mg g-1 at 313 K, 145.12 mg g-1 at 323 K and 191.27 mg g-1 at 323 K. The kinetics of the adsorption process of Pb (II) by XGFO was best defined by the pseudo-second-order model. The thermodynamic aspect of the reaction suggested that the reaction is endothermic and spontaneous. The outcomes proved that XGFO can be utilized as an efficient adsorbent material for the treatment of contaminated wastewater.

Novel ZIF-67-derived Co@CNTs nanocomposites as effective adsorbents for removal of tetracycline and sulfadiazine antibiotics

Tetracycline (TCC) and sulfadiazine (SDZ) are two of the most consumed antibiotics for human therapies and bacterial infection treatments in aquafarming fields, but their accumulative residues can result in negative effects on water and aquatic microorganisms. Removal techniques are therefore required to purify water before use. Herein, we concentrate on adsorptive removal of TCC and SDZ using cobalt@carbon nanotubes (Co@CNTs) derived from Co-ZIF-67. The presence of CNTs on the edge of nanocomposites was observed. Taguchi orthogonal array was designed with four variables including initial concentration (5–20 mg L−1), dosage (0.05–0.2 g L−1), time (60–240 min), and pH (2–10). Concentration and pH were found to be main contributors to adsorption of tetracycline and sulfadiazine, respectively. The optimum condition was found at concentration 5 mg L−1, dosage 0.2 g L−1, contact time 240 min, and pH 7 for both TCC and SDZ removals. Confirmation tests showed that Co@CNTs-700 removed 99.6% of TCC and 97.3% of SDZ with small errors (3–5.5%). Moreover, the kinetic and isotherm were studied, which kinetic and isotherm data were best fitted with pseudo second-order model and Langmuir. Maximum adsorption capacity values for TCC and SDZ were determined at 118.4–174.1 mg g−1 for 180 min. We also proposed the main role of interactions such as hydrogen bonding, π–π stacking, and electrostatic attraction in the adsorption of antibiotics. With high adsorption performance, Co@CNTs-700 is expected to remove antibiotics efficiently from wastewater.

Adsorption properties of amine modified lignin-hydrogel composite for uranyl ions: Theoretical and experimental insights

A new modified material was synthesized and characterized as ethylene diamine modified (EA) Polyacrylamide (PAA)-Lignin (L). The adsorption features of EA modified PAA-L were studied for uranyl ions. The characterization experiments were evaluated by FT-IR spectroscopic techniques, scanning electron microscopy (SEM), and PZC analysis. Adsorption of UO22+ ions as a function of concentration, pH, temperature, and time of adsorption were studied. The adsorption phenomenon of UO22+ ions onto PAA-L-EA from aqueous medium was successfully evaluated by various equilibrium models such as Langmuir, Freundlich, and Dubinin-Radushkevich (DR). The (Qe) maximum adsorption capacity values for Langmuir model was calculated as 0.792 kg mol−1 by using experimental data. The constant values of thermodynamic parameters such as (ΔG°), (ΔH°) and (ΔS°) were calculated and it has observed that the mechanism of adsorption was found compatible with endothermic and spontaneous owing to increasing disorderliness at solution/solid system. The adsorption mechanism is compatible with Elovich and intraparticle diffusion models. The power of the interaction between modified lignin and uranyl ıon was explained in the light of Hard and Soft Acid-Base Principle.

Efficient Uptake of Angiotensin-Converting Enzyme II Inhibitor Employing Graphene Oxide-Based Magnetic Nanoadsorbents

This paper reports a high efficiency uptake of captopril (CPT), employing magnetic graphene oxide (MGO) as the adsorbent. The graphene oxide (GO) was produced through an oxidation and exfoliation method, and the magnetization technique by the co-precipitation method. The nanomaterials were characterized by FTIR, XRD, SEM, Raman, and VSM analysis. The optimal condition was reached by employing GO·Fe3O4 at pH 3.0 (50 mg of adsorbent and 50 mg L−1 of CPT), presenting values of removal percentage and maximum adsorption capacity of 99.43% and 100.41 mg g−1, respectively. The CPT adsorption was dependent on adsorbent dosage, initial concentration of adsorbate, pH, and ionic strength. Sips and Elovich models showed the best adjustment for experimental data, suggesting that adsorption occurs in a heterogeneous surface. Thermodynamic parameters reveal a favorable, exothermic, involving a chemisorption process. The magnetic carbon nanomaterial exhibited a high efficiency after five adsorption/desorption cycles. Finally, the GO·Fe3O4 showed an excellent performance in CPT removal, allowing future application in waste management.

Synthesis of Chitosan-TiO2 Nanocomposite for Efficient Cr(VI) Removal from Contaminated Wastewater Sorption Kinetics, Thermodynamics and Mechanism.

A photolysis method was used to prepare a nanocomposite adsorbent (Chitosan-TiO2) and was tested for Cr(VI) removal from aqueous solution. The produce nanocomposite was investigated using, XRD, BET, FTIR, FESEM-EDX and TEM before and after Cr(VI) adsorption. The XRD results shows prepared anatase phase of TiO2 with 12 nm. According to BET measurements, the surface area of the TiO2/chitosan nanocomposite was lower and archived to 26 m2/g, while the TEM and FESEM images show a uniform distribution of TiO2 throughout the chitosan matrix. Adsorption and kinetic experiments were run in batch system under different conditions of pH, contact time, adsorbent dosage and temperature. Experimental Cr(VI) adsorption equilibrium and kinetics data fitted well to Langmuir model. The calculated Langmuir maximum adsorption capacity (qmax) value of nanocomposite was 488 mg/g. Moreover, the highest quantity of Cr(VI) uptake was achieved of pH = 2 and 45℃ and TiO2 and CS-TiO2 had respective removal efficiencies of 94 and 87.5%. The thermodynamic parameters of Cr(VI) adsorption by nanocomposite affirm the spontaneous and endothermic nature of process. Chromium adsorption mechanism by CS-TiO2 nanocomposite were proposed and discussed.

A novel hydrogel beads based copper-doped Cerastoderma edule shells@Alginate biocomposite for highly fungicide sorption from aqueous medium

The engineering of a novel biocomposite based on Cerastoderma edule shells doped with copper and alginate (Ce–Cu@Alg) forming hydrogel beads was used for batch and dynamic adsorption thiabendazole (TBZ) pesticide from water. The prepared biosorbent was analyzed by various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller analysis (BET), and energy dispersive spectroscopy (EDS), thermogravimetric and differential analysis (TGA-DTA). The results of the TBZ batch biosorption by Ce–Cu@Alg composite showed that the Langmuir model was the most adequate to describe the adsorption process, with a maximum adsorption capacity value of 21.98 mg/g. Moreover, the adsorption kinetics were adjusted by the pseudo-second-order model. The optimal conditions determined by the RSM approach coupled with the CCD design were 100 ppm of initial TBZ concentration, a Ce–Cu@Alg beads dose of 6 g/L and a contact time of 180 min for maximum removal of 83.42%. On the other hand, the TBZ sorption on a fixed bed of Ce–Cu@Alg beads was effective at high column height, low effluent flow and low solution concentration. The Thomas model was best fitted to the kinetic data. This study shows the possibility of using this new hybrid biocomposite in the industrial sector to treat large effluent volumes.

2,4-Dichlorophenoxyacetic acid (2,4-D) adsorptive removal by algal magnetic activated carbon nanocomposite

In the present study, ferric oxide nanoparticles impregnated with activated carbon from Ulva prolifera biomass (UPAC−Fe2O3) were prepared and employed to remove 2,4-Dichlorophenoxyacetic acid (2,4-D) by adsorption. The UPAC−Fe2O3 nanocomposite was characterized for its structural and functional properties by a variety of techniques. The nanocomposite had a jagged, irregular surface with pores due to uneven scattering of Fe2O3 nanoparticles, whereas elemental analysis portrayed the incidence of carbon, oxygen, and iron. XRD analysis established the crystalline and amorphous planes corresponding to the iron oxide and carbon phase respectively. FT-IR analyzed the functional groups that confirmed the integration of Fe2O3 nanoparticles onto nanocomposite surfaces. VSM and XPS studies uncovered the superparamagnetic nature and presence of carbon and Fe2O3, respectively, in the UPAC−Fe2O3 nanocomposite. While the surface area was 292.51 m2/g, the size and volume of the pores were at 2.61 nm and 0.1906 cm3/g, respectively, indicating the mesoporous nature and suitability of the nanocomposites that could be used as adsorbents. Adsorptive removal of 2,4-D by nanocomposite for variations in process parameters like pH, dosage, agitation speed, adsorption time, and 2,4-D concentration was studied. The adsorption of 2,4-D by UPAC−Fe2O3 nanocomposite was monolayer chemisorption owing to Langmuir isotherm behavior along with a pseudo-second-order kinetic model. The maximum adsorption capacity and second order rate constant values were 60.61 mg/g and 0.0405 g/mg min respectively. Thermodynamic analysis revealed the spontaneous and feasible endothermic adsorption process. These findings confirm the suitability of the synthesized UPAC−Fe2O3 nanocomposite to be used as an adsorbent for toxic herbicide waste streams.

Removal of Methylene Blue from Industrial Effluents Using Corncob Activated Carbon

Water contamination by methylene blue (MB) is a threat to human health and aquatic biota due to its toxicity, persistence, and non-biodegradability. However, there is little data available in the literature on the methylene blue removal approach from industrial effluents by corncob-activated carbon. The purpose of this study was to investigate the adsorption of methylene blue from aqueous solution and industrial effluents by corncob-activated carbon. The methylene blue adsorption capacities of corncob-activated carbon were investigated by batch adsorption experiments both in synthetic solutions and industrial effluents. The optimum pH value was 10.3 with a removal percentage of 93.4 %. Methylene blue adsorption by activated carbon followed second-order kinetics and was well fitted by the Langmuir model. The maximum adsorption capacity (Qmax) value was 11.36 mg/g. This study revealed that corncob-activated carbon has successfully removed methylene blue from industrial effluents, with percentages ranging from 65.14 %, and 76.28 %. The excellent methylene blue dye removal efficiency with corncob activated from industry effluents suggests its promising potential in remediating methylene blue contaminated wastewater.

Adsorption of lead ions (Pb2+) from wastewater using effective nanocomposite GO/CMC/FeNPs: Kinetic, isotherm, and desorption studies

In this paper, we propose a new, effective, and easy-to-implement technology for hydrothermal synthesis of an adsorption material based on carboxymethylcellulose (CMC) and graphene oxide (GO) decorated with iron nanoparticles (FeNPs) for water purification from heavy metals. The purpose was to study the effect of the iron content in the materials on their physicochemical and adsorption properties. The synthesized materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Complex adsorption studies were performed using the example of lead ion removal from contaminated aqueous media. The influence of pH and contact time on the process efficiency was studied. The mechanism of adsorption was analyzed using pseudo first-order and pseudo second-order, intraparticle diffusion, and Elovich kinetics models. The results showed an optimal pH of 6 and contact time of 30 min. The process is best described by a pseudo second-order model. The material with a mass content of iron nanoparticles of 18% (CMC/GO + Fe 18 wt%) showed the largest adsorption capacity for Pb ions (1850 mg g−1). Adsorption isotherms of lead ions from aqueous media by the synthesized composite materials were studied using Dubinin–Radushkevich and BET models. The adsorption process is based on the chemical interaction of extracted ions with the surface of an adsorbent. Desorption studies showed the possibility of using the GO/CMC/FeNPs in real processes for purification of aqueous media. The obtained maximum value of adsorption capacity for the CMC/GO + Fe 18 wt% material was 1850 mg g−1, which is one of the highest in the literature for composite materials based on GO and vegetable raw material processing products.

Copper-based metal-organic framework for highly efficient adsorption of lead ions from aqueous solution

A nanomaterial, a copper-based metal organic framework (Cu-BTC MOF), was prepared by a one-step solvothermal synthesis method and applied for the removal of Pb(II) ions from an aqueous solution via adsorption. The Cu-BTC MOF nanomaterial was characterized via x-ray diffraction, Fourier transform infrared, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX), and Brunauer–Emmett–Teller method. TEM and SEM images of the prepared Cu-BTC MOF presented octahedral crystals. Furthermore, EDX spectroscopy showed that the synthesized porous nanomaterial consisted of Cu, O, and C elements. The prepared Cu-BTC MOF was employed as an adsorbent for the removal of Pb(II) ions from an aqueous solution. Adsorption kinetics and adsorption isotherm modeling were conducted in detail. The maximum adsorption capacity values of the Cu-BTC MOF for Pb(II) ions at temperature conditions of 10, 25, and 40 °C were 890.94, 896.04, and 958.37 mg g−1, respectively. The synthesized Cu-BTC MOF showed high distribution coefficient (Kd) values, and it was very effective in extracting Pb(II) ions. In the Pb adsorption process, the molar ratio of Pb adsorption/Cu desorption was found to be close to 1 indicating that ion exchange with Cu ions in the Cu-BTC MOF material occurs and the cation exchange between Pb ions and Cu ions can be considered as a dominant mechanism of the adsorption.

Adsorption of Indigo Carmine onto Chemically Activated Carbons Derived from the Cameroonian Agricultural Waste Garcinia cola Nut Shells and Desorption Studies

In the quest for a sustainable environment and clean water resources, the efficacy of activated carbons synthesized from Garcinia cola nut shells impregnated with KOH (CBK1/1) and ZnCl2 (CBZ1/1) for the adsorption of indigo carmine (IC) dye was studied using the batch technique. The prepared activated carbons were characterized using iodine number, elemental analysis, scanning electron microscopy (SEM), FTIR spectroscopy, powder X-ray diffraction (XRD), TGA/DTA, Boehm titration, and pH at point of zero charge. The elemental analysis showed a high percentage of carbon in both activated carbons (ACs). FTIR and Boehm titration analysis indicated the presence of several functional groups on the surfaces of both ACs which could influence the adsorption of IC. The primary adsorption mechanisms involved electrostatic interaction, hydrogen bonds formation, and π−π interactions. Maximum adsorption capacity values obtained using the Fritz–Schlunder III three-parameter model were 19.019 mg·g−1 and 18.299 mg·g−1 for CBK1/1 and CBZ1/1, respectively. The Fritz–Schlunder model exponent mFS of value less than 1 showed that the adsorption of IC by the ACs occurred on heterogeneous surfaces. Positive values of ∆Q obtained by the linear and nonlinear forms of the Temkin model indicate the exothermic character of the adsorption process.

Effective Recovery of Palladium(II) Ions using Chitosan-Based Adsorbent Material

Chitosan is one of the naturally abundant, biodegradable, and low-cost adsorbent materials for metal adsorption purposes. In this work, we evaluated the application of chitosan materials derived from seafood wastes in Depok beach, Yogyakarta, for an effective recovery of the palladium(II) ions. First of all, the seafood wastes were treated to obtain chitin and then followed by the deacetylation process to produce chitosan material with a deacetylation degree of 78.42%. The chitosan material was characterized using Fourier transform infrared (FTIR) spectrophotometer. It was found that chitosan gave high adsorption percentage (90%) for palladium(II) ions due to the complexation with hydroxyl, amino and carbonyl functional groups. The palladium(II) adsorption onto chitosan material followed the pseudo-second-order (R2 = 0.9978) and Langmuir (R2 = 0.9979) models for kinetic and isotherm experiments, respectively, with a maximum adsorption capacity value of 0.70 mmol g-1. The palladium(II) ions could be easily desorbed in 90% percentage using 1.0 M HCl solution from metal-laden chitosan to regenerate the adsorbent material. The chitosan-based adsorbent material did not lose its adsorption capability after three consecutive cycles with no significant structural change as revealed from the FTIR data. These results showed the potential application of natural chitosan materials derived from seafood wastes for the effective recovery of palladium(II) ions.

Adsorption of Heavy Metals from Small-Scale Gold Processing in Baguio Mining District, Philippines

Small-scale mining in the Philippines lacks research and technologies for the application of an inexpensive and environmentally sound treatment of its wastewaters. Hence, laboratory-scale fixed-bed column tests were carried out to test and evaluate the sorbent adsorption performance of the Philippine Natural Bentonite (PNB) and the Philippine Natural Zeolite (PNZ) against the heavy metals present in the ball mill facilities within the Baguio Mining District. Results showed that removal percentages of PNB and PNZ in terms of lead (Pb) concentrations are 50.43% and 26.90%, respectively. Moreover, the dynamic uptake capacity and maximum adsorption capacity values of PNB showed greater values than PNZ and the sorption models, Bohart-Adams, Wolborska, Thomas, and Yoon-Nelson models, displayed good fit for the breakthrough curves. Furthermore, varying the flow rate and bed height manifested that an increase in flow rate yields a lesser saturation time while the rise in bed height increases uptake capacity, saturation time, and removal percentage of the system. Regarding the cost efficiencies of the sorbents, the study revealed that PNB is more cost-efficient than PNZ since only 1.13 Philippine pesos of PNB is required to remove a gram of Pb compared to PNZ, which costs 3.5 pesos. Therefore, this research concluded that PNB could be a better sorbent of Pb in terms of removal percentage and cost-efficiency. The study recommends further regeneration studies for the reusability of the sorbents after exhaustion and hopes that this research will be a springboard for further environmental studies.

Zeolite Waste Characterization and Use as Low-Cost, Ecofriendly, and Sustainable Material for Malachite Green and Methylene Blue Dyes Removal: Box–Behnken Design, Kinetics, and Thermodynamics

This study investigated the potential of 4A zeolite, named4AZW in this work, generated by natural gas dehydration units as solid waste after several treatment cycles, as a low-cost adsorbent to separately remove two cationic dyes, methylene blue (MB) and malachite green (MG), from an aqueous solution within a batch process. The adsorbent material was characterized by N2gas adsorption–desorption, X-ray fluorescence spectrometry, X-ray diffraction, FT-IR spectroscopy, and the determination of its cation exchange capacity and point of zero charge. The influence of key operating parameters, such as the pH, adsorbent dosage, ionic strength, contact time, initial dye concentration, and temperature, was investigated. Three independent variables acting on MB adsorption performance were selected from the Box–Behnken design (BBD) and for process modeling and optimization. An analysis of variance (ANOVA), an F-test, and p-values were used to analyze the main and interaction effects. The experimental data were satisfyingly fitted with quadratic regression with adjusted R2= 0.9961. The pseudo-second-order kinetic model described the adsorption of the dyes on 4AZW. The equilibrium data were well-fitted by the Langmuir model for each adsorption system (MB-4AZW and MG-4AZW) with maximum adsorption capacity (qmax) values of 9.95 and 45.64 mg/g, respectively, at 25 °C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic.

Evaluation of a Causative Species of Harmful Algal Blooming, Prorocentrum triestinum, as a Sustainable Source of Biosorption on Cadmium

Biosorption is an effective method for removing heavy metal ions from wastewater. In the current study, the biosorption capacity of a microalgae Prorocentrum triestinum strain AD1 was investigated for cadmium removal. The efficient biomass concentration was found to be 5 g/L. Based on the Langmuir adsorption model, the maximum adsorption capacity (qmax) value of cadmium removal was found to be 0.0196 mmol/g. The investigation results of the AD1 biosorption kinetics showed that the effective contact time on biosorption was 3 h, and the adsorption kinetics fitted well with the pseudo-second-order model. The optimum pH of biosorption was found to be 5. On the other hand, HCl could act as an efficient desorbent for cadmium recovery from AD1, with an optimum concentration of 0.01 M. These results suggest that the biomass of P. triestinum has great potential for the removal of cadmium from wastewater as an efficient biosorbent.