Biosorption Removal of Methylene Blue Dye from Aqueous Solutions using Phosphoric Acid-Treated Balanites Aegyptiaca Seed Husks Powder

Water contamination caused by the presence of synthetic dye is one of the world's major environmental concerns. This work aims to explore the potential application of non-carbonized phosphoric acid-treated Balanites aegyptiaca "heglig" seed husks powder (BASHP) as a bio-sorbent for methylene blue (MB) removal from water bodies. BASHP was characterized using Fourier transform infrared spectroscopy (FTIR). The characteristics of BASHP, such as the iodine number, point of zero charges, solubility, and specific surface area (SMB) were also estimated. The biosorption of MB onto the BASHP surface was studied in batch mode under various conditions (contact time, shaking speed, solution temperature, initial solution pH, ionic strength, initial dye concentration, and biosorbent dosage). The adsorption kinetics and isotherm were better described by pseudo-second-order and Langmuir models, respectively. More than 97% of MB was removed, and the maximum biosorbed amount of MB (qmax) was 72.99 mg/g. Thermodynamics findings revealed that the proposed biosorption is an endothermic and spontaneous process. These findings showed that BASHP is a potentially eco-friendly, easily available, and low-cost material for removing hazardous dyes (e.g., methylene blue) from an aquatic environment, as well as a promising method for reducing agricultural solid waste (e.g., seed husks).

Lignocellulose-Based Superabsorbent Polymer Gel Crosslinked with Magnesium Aluminum Silicate for Highly Removal of Zn (II) from Aqueous Solution

Lignocellulose (LCE) was ultrasonically treated and intercalated into magnesium aluminum silicate (MOT) clay to prepare a nano-lignocellulose magnesium aluminum silicate polymer gel (nano-LCE-MOT) for the removal of Zn (II) from aqueous solution. The product was characterised using nitrogen adsorption/desorption isotherm measurements, Fourier-transform infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The conditions for the adsorption of Zn (II) on nano-LCE-MOT were screened, and adsorption kinetics and isotherm model analysis were carried out to explore the adsorption mechanism and achieve the optimal adsorption of Zn (II). Optimal adsorption was achieved at an initial Zn (II) concentration of 800 mg/L at 60 °C in 160 min at a pH of 4.52. The adsorption kinetics were explored using a pseudo-second-order model, with the isotherm adsorption equilibrium found to conform to the Langmuir model. The maximum adsorption capacity of the nano-LCE-MOT polymer gel toward Zn (II) is 513.48 mg/g. The materials with adsorbed Zn (II) were desorbed using different media, with HCl found to be the most ideal medium to desorb Zn (II). The optimal desorption of Zn (II) was achieved in 0.08 mol/L HCl solution at 65 °C in 60 min. Under these conditions, Zn (II) was almost completely desorbed from the adsorbents, with the adsorption effect after cycling being slightly different from that of the initial adsorption.

Superhigh Adsorption of Cadmium(II) Ions onto Surface Modified Nano Zerovalent Iron Composite (CNS-nZVI): Characterization, Adsorption Kinetics and Isotherm Studies

The efficiency of surface modified nanoscale zerovalent iron (nZVI) composite by cashew nut shell (CNS) was tested for the removal of cadmium ions from the aqueous solutions. 2 g/l CNS-nZVI was efficient for 98% removal. The adsorption capacity was 35.58 mg/g. The Freundlich isotherm (R2 = 0.9769) and the pseudo-second order adsorption kinetics data fitted well. This proved CNS-nZVI has a high removal efficiency for Cd(II) from aqueous solutions.

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently, metal–organic frameworks (MOFs) have received considerable attention as highly efficient adsorbents for dye wastewater remediation. However, the immobilization of MOFs on the substrate surfaces to fabricate easy recyclable adsorbents via a facile route is still a challenge. In this work, ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method. The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR, XRD, XPS, SEM and BET analysis, respectively. As expected, the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green (MG). Meanwhile, the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model, respectively. Moreover, its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aqueous solution. Most importantly, the ZIF-67/cotton fibers can remove MG from synthetic effluents, and it can be easily regenerated without filtration or centrifugation processes, with the regeneration efficiency remaining over 90% even after 10 cycles. Additionally, the ZIF-67/cotton fibers presented excellent antimicrobial performance against E. coli and S. aureus. Hence, the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Removal of phosphate from aqueous solution by chitosan coated and lanthanum loaded biochar derived from urban dewatered sewage sludge: adsorption mechanism and application to lab scale columns

A lanthanum modified sludge biochar chitosan (La-SBC-CS) microsphere was successfully synthesized by dropping sludge biochar (BC) and chitosan into an Lanthanum chloride solution. Batch adsorption experiments were conducted to investigate the adsorption kinetics and isotherm. Application of continuous phosphate removal was achieved via lab-scale column reactors. The phosphate adsorption equilibrium data of the La-SBC-CS fitted well with the Freundlich isotherm, with a maximum adsorption amount of 81.54 mg p/g at 25 °C. Characterization of the adsorbent using scanning electron microscopy analysis (SEM), X ray energy spectrum analysis (EDS), X-ray diffraction analysis (XRD) and Fourier infrared analysis (FTIR) techniques suggested that the possible adsorption mechanisms were electrostatic interaction, ligand exchange and complexation. The La-SBC-CS kept 76.37% phosphate removal efficiency after eight recycles. The results of continuous column reactor experiment demonstrated that the breakthrough time increased with an increase in adsorbents filling height, while it decreased with an increase in initial phosphate concentration or flow velocity. YOON model was applied to the continuous experimental data to predict breakthrough curves and determined the characteristic adsorption parameters for process design. This study indicated that the potential for the practical application of La-SBC-CS in phosphate removal from wastewater.

Adsorption Kinetics and Isotherm Study of Basic Red 5 on Synthesized Silica Monolith Particles

The Silica monolith particles (SMP) were prepared from Tetra-Methyl-Ortho-Silicate (TMOS) and characterized by Fourier transforms infrared (FTIR), Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface area analyzer. FTIR analysis showed the Si−O stretching confirming SMP formation. SEM analysis provided information about the mean diameter of SMP (1−5 µm). EDX confirmed the presence of silicon and oxygen in the SMP. Moreover, the calculated surface area for SMP was found to be around 367 m2/g, whereas BJH pore size distributed particles were 87.15 along with the total pore volume and pore radius of 0.073 cm3/g and 16.627 Å, respectively. Besides, the removal efficiency was found to be about 96%. Various kinetic equations were used to calculate the adsorption parameters. Overall, the results show that the most appropriate model for the kinetics data was the pseudo-second order kinetics model while the mechanism of adsorption was best explained by the Langmuir isotherm. The highest removal of Basic Red 5 dye after 120 min at 298 K was 576 mg/g. Moreover, the thermodynamics parameters (Enthalpy, Gibb’s energy, and Entropy) were also estimated. The ΔH° (0.995 kJ/mol) value depicted the endothermic nature of the process. The non-spontaneous aspect of the process was evident from the ΔG° values which were 60.431, 328.93, and 339.5 kJ/mol at 293, 303, and 313 K, respectively. From the high removal efficiency value, it can be concluded that the prepared adsorbent can be a potential adsorbent in the reclamation of dyes from wastewater.

Trimethylamine functionalized radiation-induced grafted polyamide 6 fibers for p-nitrophenol adsorption

The method of pre-irradiation grafting was used with the aid of electron beam (EB) accelerator to accomplish the grafting of polyamide 6 fibers (PA6) with glycidyl methacrylate (GMA). The extent to which GMA was grafted on PA6 was found to be markedly influenced by the absorbed dose of radiation and the reaction time of grafting. Trimethylamine (TMA) was afterwards employed for the functionalization of GMA-grafted fibers (PA6-g-GMA). A range of analyses (e.g., FTIR, FESEM, XRD, BET, and pHpzc) were carried out to determine the physiochemical and morphological properties of the fibrous adsorbent. p-Nitrophenol (PNP) adsorption from aqueous solution was conducted with the resulting TMA-(PA6-g-GMA) adsorbent. The adsorption behaviour of PNP on the fibrous adsorbent was clarified by investigating the adsorption kinetics and isotherm. According to the results, the adsorption of PNP on TMA-(PA6-g-GMA) reflected the pseudo-second order model. Meanwhile, the isotherm analysis revealed that the best description of the equilibrium data was provided by Redlich–Peterson model, followed closely by Langmuir isotherm model. The achieved adsorption capacity was highest at 176.036 mg/g. Moreover, the adsorption was indicated by the thermodynamic analysis to be spontaneous and exothermic. Regeneration and recycling of the adsorbent was possible for a minimum of five cycles with no reduction in adsorption capacity. It was concluded that the fibrous adsorbent could have applications for the removal of PNP at industrial pilot scale.

Selective recovery of platinum from spent autocatalyst solution by thiourea modified magnetic biocarbons

The precious platinum group metals distributed in urban industrial products should be recycled because of their rapid decline in the contents through excessive mining. In this work, thiourea modified magnetic biocarbons are prepared via an energy-efficient microwave-assisted activation and assessed as potential adsorbents to recover platinum ions (i.e., Pt(IV)) from dilute waste solution. The physicochemical properties of prepared biocarbons are characterized by a series of spectroscopic and analytic instruments. The adsorption performance of biocarbons is carried out by using batch tests. Consequently, the maximum adsorption capacity of Pt(IV) observed for adsorbents is ca. 42.8 mg g−1 at pH = 2 and 328 K. Both adsorption kinetics and isotherm data of Pt(IV) on the adsorbents are fitted better with non-linear pseudo second-order model and Freundlich isotherm, respectively. Moreover, the thermodynamic parameters suggest that the Pt(IV) adsorption is endothermic and spontaneous. Most importantly, the adsorbents exhibit high selectivity toward Pt(IV) adsorption and preserve ca. 96.9% of adsorption capacity after six cyclic runs. After adsorption, the regeneration of the prepared adsorbents can be effectively attained by using 1 M thiourea/2% HCl mixed solution as an eluent. Combined the data from Fourier transform infrared and X-ray photoelectron spectroscopies, the mechanisms for Pt(IV) adsorption are governed by Pt–S bond between Pt(IV) and thiourea as well as the electrostatic attraction between anionic PtCl62− and cationic functional groups of adsorbents. The superior Pt(IV) recovery and sustainable features allow the thiourea modified magnetic biocarbon as a potential adsorbent to recycle noble metals from spent autocatalyst solution.

Fabrication of PVA/ GO Nanofiber Films by Electrospinning: Application for the Adsorption of Cu2+ and Organic Dyes

In recent years, the treatment of water pollution has been a challenging and far-reaching topic. In order to improve the adsorption performance of polyvinyl alcohol nanofibers, a new nano-adsorbent graphene oxide was introduced into them in this work. The introduction of GO greatly increases the adsorption of Cu2+, Methylene blue (MB) and Congo Red (CR). The adsorption kinetics and isotherm analysis of the PVA/GO nanofiber film during the adsorption process showed that the adsorption of Cu2+ and MB by PVA/GO nanofiber film was mainly chemical adsorption, while the adsorption of CR was mainly physical adsorption. The adsorption process of PVA/GO nanofiber film on Cu2+ was in line with the Langmuir isothermal adsorption model, that is, single molecular layer adsorption, the distribution of adsorption active sites was relatively uniform, and the increasing temperature was more conducive to the adsorption of Cu2+.