Synthesis of a novel 3,5-diacrylamidobenzoic acid based hyper-cross-linked resin for the efficient adsorption of Congo Red and Rhodamine B

Melamine-based hyper-cross-linked resin for efficient removal of total petroleum hydrocarbons (C10-C32) from aqueous solutions

Petroleum hydrocarbons (PHCs) are produced from industrial discharges, storage leakages, accidental spills, and operational failures. The hazardous nature of PHCs causes serious health risks and threatens the entire aquatic habitat. In this research work, the investigation of the removal of total petroleum hydrocarbons (TPHs) from the contaminated water is carried out utilizing a novel hypercross-linked resin, MAICY, which is generated by condensation of commercially available precursors. The chemical structures of MAICY have been examined extensively by FESEM, FT-IR, solid (CP-MAS) 13C-NMR, and TGA. A comprehensive analysis for adsorption parameters of TPHs has been performed, and different models such as Langmuir and Freundlich isotherms have been employed where the Freundlich isotherm was found to be the best fit for removal of THPs (R2= 0.9991). The results revealed that the performance of MAICY for the adsorption of TPHs from contaminated water gives a maximum adsorption capacity (qe) of 146 mg.g-1. The results of various parameters hinted that the contact time (0.25-4 h), the dosage of adsorbent (0.17 g/L), pH (7), and concentration of TPHs (26.5 mg/L) have controlled the overall adsorptive performance. Moreover, the kinetic data of qe(expt.) and qe(calc.) for adsorption of TPHs disclosed the regression values (R2) for pseudo-first order (R2= 0.9921) and pseudo-second order (R2= 0.9891). Additionally, based on CHI factor (X2) error estimations, the data was shown to be more consistent with pseudo-first-order kinetics. Moreover, MAICY demonstrated excellent reusability and recycling properties for up to four consecutive adsorption-desorption cycles.

Waste remediation: Low-temperature synthesis of hybrid Cu(OH)2/CuO and CuO nanostructures from spent printed circuit boards and their dye degradation studies

The demand for environmentally friendly and sustainable resource utilization techniques for recycling waste printed circuit boards is significant due to their status as valuable secondary resources, containing high-purity copper and precious metals. In this context, Cu(OH)2/CuO and CuO nanostructures were fabricated using alkaline precipitation and low-temperature aging methods using the strip solution originated from laboratory-scale spent mobile phone printed circuit board recovery process. XRD, FTIR, FESEM-EDX, and TEM were utilized to characterize the as-recovered nanoproducts. A hybrid structure of Cu(OH)2/CuO was formed at 70°, and monoclinic CuO phase was formed at 80 °C aging time. The results show that Cu(OH)2/CuO nanoflakes have an average crystallite size of 24.06 nm and a particle width of 22 ± 3 nm. Cu(OH)2/CuO nanoflakes formed at 70 °C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80 °C aging temperature. The optical band gap energy of Cu(OH)2/CuO and CuO nanostructures formed was found to be 2.28 eV and 2.22 eV, respectively. The hybrid Cu(OH)2/CuO nanostructure photocatalyzed the decomposed 97.28% rhodamine blue using a visible light source, whereas the CuO nanostructure degraded only 14.64% rhodamine blue dye under similar conditions. A surfactant-less hybrid structure is developed without the use of any chemical precursor. Thus, a high value-added product is produced using one waste material to remove another waste in wastewater treatment.

Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red

Attapulgite (APT) is widely used in wastewater treatment due to its exceptional adsorption and colloidal properties, as well as its cost-effectiveness and eco-friendliness. However, low-grade APT generally limits its performance. Here, a colloid mill-assisted ultrasonic-fractional centrifugal purification method was developed to refine low-grade APT. This process successfully separated and removed impurity minerals such as quartz and dolomite from the raw ore, resulting in a refined APT purity increase from 16.9% to 60% with a specific surface area of 135.5 m2∙g-1. Further modifying of the refined APT was carried out through the hydrothermal method using varying dosages of cetyltrimethylammonium chloride (CTAC), resulting in the production of four different APT adsorbents denoted as QAPT-n (n = CTAC mole number) ranging from 0.5 to 5 mmol. Using Congo red (CR) as the target pollutant, the QAPT-5 sample exhibited the best adsorption capacity with the maximum quantity of 1652.2 mg∙g-1 in a neutral solution at 30 °C due to the highest surface charge (zeta potential = 8.25 mV). Moreover, the QAPT-5 pellets (~2.0 g adsorbent) shaped by the alginate-assisted molding method removed more than 96% of 200 mL aqueous solution containing 200 mg∙L-1 CR and maintained this efficiency in 10 adsorption-elution cycles, which exhibited the promising practical application.

A comprehensive review on the application of semiconducting materials in the degradation of effluents and water splitting

In this comprehensive review article, we delve into the critical intersection of environmental science and materials science. The introduction sets the stage by emphasizing the global water shortage crisis and the dire consequences of untreated effluents on ecosystems and human health. As we progress into the second section, we embark on an intricate exploration of piezoelectric and photocatalytic principles, illuminating their significance in wastewater treatment and sustainable energy production. The heart of our review is dedicated to a detailed analysis of the detrimental impacts of effluents on human health, underscoring the urgency of effective treatment methods. We dissected three key materials in the realm of piezo-photocatalysis: ZnO-based materials, BaTiO3-based materials, and bismuth-doped materials. Each material is scrutinized for its unique properties and applications in the removal of pollutants from wastewater, offering a comprehensive understanding of their potential to address this critical issue. Furthermore, our exploration extends to the realm of hydrogen production, where we discuss various types of hydrogen and the role of piezo-photocatalysis in generating clean and sustainable hydrogen. By illuminating the synergistic potential of these advanced materials and technologies, we pave the way for innovative solutions to the pressing challenges of water pollution and renewable energy production. This review article not only serves as a valuable resource for researchers and scholars in the fields of material science and environmental engineering but also underscores the pivotal role of interdisciplinary approaches in addressing complex global issues.

Green synthesis of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through Michael addition for the treatment of heavy metals and organic dyes contaminated wastewater

Environmental pollution is the greatest challenge of the modern age due to unprecedented industrialization and urbanization that has led to the contamination of water resources with a wide range of pollutants. The release of untreated industrial and municipal wastewater to water bodies further intensifies the problem. The presence of heavy metals and organic contaminants in water poses significant threats to humans, aquatic life, and the environment. Adsorption is one of the famous water treatment technologies due to its simplicity, low cost, efficiency, and minimal secondary pollution. The selection or synthesis of an effective adsorbent is key to the success of the adsorptive removal of pollutants. In this work, we synthesized an adsorbent consisting of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through a single-step Michael addition reaction. The adsorbent was characterized by FTIR, PXRD, TGA, SEM, and TEM to investigate its functional moieties, material nature, thermal, morphological, and internal structural features, respectively. Due to its mesoporous structure, presence of functional groups, and 3D hyper-cross-linked network, it efficiently removed heavy metals (Cd, Cr, and Pb) from aqueous media. The effect of various parameters such as sample pH, adsorbent dosage, contact time, and adsorbate concentrations was thoroughly investigated. The experimental data were analyzed by a variety of isotherm models wherein Langmuir was found to be the best fit for explaining the adsorption of all the metals. The adsorption kinetics was best explained by the pseudo-second-order model. The maximum adsorption capacities for Cd, Cr, and Pb were 60.98 mg g-1, 119 mg g-1, and 9.302 mg g-1, respectively. The synthesized adsorbent was also tested for removal of organic dyes, and it showed selective and fast removal of Eriochrome Black T. Polymeric resins can be promising materials for adsorptive remediation of pollutants in aqueous media.

"Functional connector" strategy on tunable organo-vermiculites: The superb adsorption towards Congo Red

With the increasingly worldwide concentration of environmental pollution, exploiting cost-effective adsorbents has been a research hotspot. Here we introduce novel "functional connector" amide-containing gemini surfactants (LDAB, LDAPP, LDAMP and LDABP) and apply to modify Na-vermiculite (Na-Vt) for Congo red (CR) removal. Chain amide as the functional connector in the modifier, increases 6.9 times of CR uptake than traditional organo-Vts, which is further enhanced by tunning the functional group of modifier spacers. Superb uptake of CR on organo-Vts reaches 1214.05, 1375.47 and 1449.80 mg/g, and the removal efficiencies achieve 80.94%, 91.70% and 96.65% on LDAB-Vt, LDAPP-Vt and LDAMP-Vt, respectively. Notably, the maximum experimental adsorption capacity of LDAPP-Vt is 1759.64 mg/g. These experimental values are among the highest reported CR adsorbents. A combination experimental and theoretical analysis is conducted to unveil the structure-adsorptivity relationship: (i) Adsorptivity enhancement of organo-Vts is more effectively by regulating functional chains than the functional spacer. (ii) para-substituted aromatic spacers own the best adsorptive configuration and strongest stability for π-π interaction. (iii) π-π interaction provided by isolated aromatic ring is stronger than biphenyl, whose steric hindrance depresses the adsorptivity. Results in this study not only explain a new "functional connector" strategy to Vt-based adsorbents, but also provide a practical designing strategy for organic adsorbents characterized with high uptake capacity.

Facile synthesis of CoFe2O4@MIL-53(Al) nanocomposite for fast dye removal: Adsorption models, optimization and recyclability

The global occurrence of textile dyes pollution has recently emerged, posing a serious threat to ecological systems. To abate dye contamination, we here developed a novel magnetic porous CoFe₂O₄@MIL-53(Al) nanocomposite by incorporating magnetic CoFe₂O₄ nanoparticles with MIL-53(Al) metal-organic framework. This nanocomposite possessed a surface area of 197.144 m² g^-1 and a pore volume of 0.413 cm³ g^-1. The effect of contact time (5-120 min), concentration (5-50 mg L^-1), dosage (0.1-1.0 g L^-1), and pH (2-10) on Congo red adsorption was clarified. CoFe₂O₄@MIL-53(Al) could remove 95.85% of Cong red dye from water with an accelerated kinetic rate of 0.6544 min^-1 within 10 min. The kinetic and isotherm models showed the predominance of Bangham and Temkin. According to Langmuir, the maximum uptake capacities of CoFe₂O₄@MIL-53(Al), CoFe₂O₄, and MIL-53(Al) adsorbents were 43.768, 17.982, and 15.295 mg g^-1, respectively. CoFe₂O₄@MIL-53(Al) was selected to optimize Cong red treatment using Box-Behnken experimental design. The outcomes showed that CoFe₂O₄@MIL-53(Al) achieved the highest experimental uptake capacity of 35.919 mg g^-1 at concentration (29.966 mg L^-1), time (14.926 min), and dosage (0.486 g L^-1). CoFe₂O₄@MIL-53(Al) could treat dye mixture (methylene blue, methyl orange, Congo red, malachite green, and crystal violet) with an outstanding removal efficiency of 81.24% for 30 min, and could be reused up to five cycles. Therefore, novel recyclable and stable CoFe₂O₄@MIL-53(Al) is recommended to integrate well with real dye treatments systems.

Efficient Congo Red Removal Using Porous Cellulose/Gelatin/Sepiolite Gel Beads: Assembly, Characterization, and Adsorption Mechanism

Porous sustainable cellulose/gelatin/sepiolite gel beads were fabricated via an efficient 'hydrophilic assembly-floating droplet' two-step method to remove Congo red (CR) from wastewater. The beads comprised microcrystalline cellulose and gelatin, forming a dual network framework, and sepiolite, which acted as a functional component to reinforce the network. The as-prepared gel beads were characterized using FTIR, SEM, XRD, and TGA, with the results indicating a highly porous structure that was also thermally stable. A batch adsorption experiment for CR was performed and evaluated as a function of pH, sepiolite addition, contact time, temperature, and initial concentration. The kinetics and isotherm data obtained were in agreement with the pseudo-second-order kinetic model and the Langmuir isotherm, with a maximum monolayer capacity of 279.3 mg·g^-1 for CR at 303 K. Moreover, thermodynamic analysis demonstrated the spontaneous and endothermic nature of the dye uptake. Importantly, even when subjected to five regeneration cycles, the gel beads retained 87% of their original adsorption value, suggesting their suitability as an efficient and reusable material for dye wastewater treatments.

Removal of hazardous dyes, toxic metal ions and organic pollutants from wastewater by using porous hyper-cross-linked polymeric materials: A review of recent advances

Water quality plays a central role in the well-being of all the living organisms on planet Earth. The ever-increasing human population and consequently increasing industrialization, urbanization, and chemically boosted cultivation are rapidly contaminating already stressed water resources. The availability of clean drinking water has become scarce for masses across the globe, and this situation is becoming alarming in developing countries. Therefore, the immediate need for cost-effective, easily accessible, eco-friendly, portable, thermally efficient, and chemically stable technologies and materials is desperately felt to meet the high global demand for clean water. To search for effective materials for wastewater treatment, the hyper-cross-linked porous polymers (HCPs) have emerged as an excellent class of porous materials for wastewater treatment due to their unique features of high surface area, tunability, biodegradability, and chemical versatility. This review describes the advances in fabrication strategies and the efficient utilization of hyper-cross-linked porous polymers for wastewater treatment. Moreover, this review specifically discusses the hyper-cross-linked porous polymers effectiveness for the separation of the dyes, nutrients, inorganic ions, organic contaminants, and toxic metals ions. Finally, the review provides insight into the challenges and prospects in the area of hyper-cross-linked porous polymers. Overall, the hyper-cross-linked porous polymers with empowering proper functionalization can provide an opportunity for the wastewater treatment not only to remove toxic contaminants but also to make contaminated water useful for various applications.

Review on nickel-based adsorption materials for Congo red

Excessive synthetic dyestuffs in the aquatic environment pose various ecological and health issues that are detrimental to sustainable development. Adsorption is considered a feasible technique of eliminating dye pollutants from the water environment because of its advantages of high efficiency, low cost, easy operation, and absence of secondary pollution. Among the many dyes, Congo red (CR) is a widely used azo dye. Nickel-based materials, including nickel hydroxide, nickel oxide, nickel-containing layered double hydroxides, nickel-based spinel and metal-organic frameworks, metallic nickel, nickel-based sulfide, and nickel composites, have been extensively studied for CR adsorption due to their morphological diversity, large specific surface area, and strong affinity toward CR. However, fabricating nickel-based adsorbents with high efficiency and stability and excellent recyclability for practical application remains a challenge. This review outlines the research progress of nickel-based materials in CR adsorption. The interaction between CR molecules and nickel-based adsorbents is systematically presented, and the possible adsorption mechanisms are summarized. Finally, the challenges and future development directions of the practical application of nickel-based adsorbent materials are proposed.

Instantaneous Adsorption of Synthetic Dyes from an Aqueous Environment Using Kaolinite Nanotubes: Equilibrium and Thermodynamic Studies

Innovative kaolinite nanotubes (KNTs) are synthesized utilizing a simple technique involving a sonication-induced exfoliation process, followed by chemical scrolling reactions. The KNTs as a material have high reactivity and promising surface area to be used in the purification of water from cationic dyes (safranin (SF) and malachite green (MG)) and anionic dyes (methyl orange (MO) and Congo red (CR)). The kinetic studies of the four dyes SF, MG, CR, and MO show an equilibration time interval of 240 min. The SF, MG, CR, and MO dyes' uptake reactions are in agreement with the kinetic behavior of the pseudo-first-order model and the equilibrium properties of the Langmuir model. Such modeling results, in addition to the Gaussian energies from the Dubinin-Radushkevich (D-R) model (SF (1.01 kJ/mol), MG (1.08 kJ/mol), CR (1.11 kJ/mol), and MO (1.65 kJ/mol)), hypothesize monolayer adsorption of the four dyes by physical reactions. The KNTs show theoretical q max values of 431.6, 489.9, 626.2, and 675.5 (mg/g) for SF, MG, CR, and MO, respectively. The thermodynamic examination of SF, MG, CR, and MO adsorption reactions using KNTs verifies their adsorption by exothermic and spontaneous reactions. The KNT adsorbents achieve promising adsorption results in the presence of different coexisting ions and show significant recyclability properties. Therefore, the production of KNTs from kaolinite shows a strong effect on inducing the textural, physicochemical, and adsorption properties of clay layers as well as their affinity for different species of synthetic dyes.

Photocatalytic Degradation of Alizarin Red S, Amaranth, Congo Red, and Rhodamine B Dyes Using UV Light Modified Reactor and ZnO, TiO2, and SnO2 as Catalyst

The photocatalytic degradation of dyes (alizarin red S, amaranth, congo red, and rhodamine B) present in wastewater was performed with UV lamp. The catalysts employed for this investigation were ZnO, TiO2, and SnO2. The kinetic studies of dyes degradation followed first order reaction. ZnO was found to be most efficient photo-catalyst for degrading these dyes. The optimal result for alizarin red S was k = 0.2118 min−1, t1/2 = 3.27 min, and R2 = 0.7998, for amaranth was k = 0.146 min−1, t1/2 = 4.74 min, and R2 = 0.8348, for congo red was k = 0.2452 min−1, t1/2 = 2.8 min, and R2 = 0.8382, and for rhodamine B was k = 0.1915 min−1, t1/2 = 3.6 min, and R2 = 0.76.

Batch and fixed-bed adsorption behavior of porous boehmite with high percentage of exposed (020) facets and surface area towards Congo red

Boehmite adsorbents with high percentage of exposed (020) facets and large specific surface area were prepared by a separate nucleation and aging steps route with excellent performance towards Congo red in batch and fixed-bed adsorption columns.

Microwave-assisted hydrothermal assembly of 2D copper-porphyrin metal-organic frameworks for the removal of dyes and antibiotics from water

Adsorption and photocatalysis are promising strategies to remove pollutants of dyes and antibiotics from wastewater. In this study, we demonstrate a rapid microwave-assisted hydrothermal route for the assembly of 2D copper-porphyrin Metal-Organic Frameworks (Cu-TCPP MOFs) within 1 h. The resulting 2D Cu-TCPP nanosheets with excellent crystallinity and a large surface area (342.72 m²/g) exhibited outstanding adsorption performance for typical dyes with adsorption capacities of about 185 mg/g for rhodamine B, 625 mg/g for methylene blue, and 290 mg/g for Congo red, respectively, as well as for representative antibiotics with adsorption capacities of about 130 mg/g for oxytocin, 150 mg/g for tetracycline, and 50 mg/g for norfloxacin, respectively. Meanwhile, the as-prepared 2D Cu-TCPP showed good photocatalytic degradation activity of pollutants after adsorption under irradiation by visible light, reaching removal efficiencies of 81.2 and 86.3% toward rhodamine B and norfloxacin, respectively. These results demonstrate the promising potential of 2D Cu-TCPP for use in the removal of contaminants from wastewater.

Green microwave synthesis of functionalized chitosan with robust adsorption capacities for Cr(VI) and/or RHB in complex aqueous solutions

Dinitrosalicylic acid-functionalized chitosan, CHN-DNSA, was developed and improved the adsorption property against chromium Cr(VI) and/or Rhodamine B (RHB). Here, the disposal of wastewater bearing Cr(VI) and RHB from a complex system was ascribed to significant differences in physicochemical properties. The constructed CHN-DNSA surface charge is responsible for different interactions enabling simultaneous capture of pollutants. The excellent adsorption potency of Cr(VI) at pH 3.0 was 98.4% within a remarkable 1 h and the adsorption performance was 91.1% for RHB. The ionic strength was affected, reducing the removal % of Cr(VI) to 36.7% whereas 0.1 M NaCl meliorated the removal efficiency from 91.6 to 96.2% for RHB and from 82.3 to 89.1% for a binary system. Also, the exploited elimination process of Cr(VI) and/or RHB obeyed the 2nd model of kinetics and the Freundlich system. Good recovery, superior capacity, and synthetic approach make this protocol promising for wastewater treatment.

Processable dispersions of photocatalytically active nanosheets derived from titanium diboride: self assembly into hydrogels and paper-like macrostructures

Titanium diboride (TiB₂), a layered ceramic material, is well-known for its ultrahigh strength, wear resistance, and chemical inertness. In this work, we present a simple one-pot chemical approach that yields sheet-like nanostructures from TiB₂. We serendipitously found that TiB₂ crystals can undergo complete dissolution in a mild aqueous solution of H₂O₂ under ambient conditions. This unexpected dissolution of TiB₂ is followed by non-classical recrystallization that results in nanostructures with sheet-like morphology exhibiting Ti-O and B-O functional groups. We show that this pathway can be used to obtain an aqueous dispersion of nanosheets with concentrations ≥3 mg mL^-1. Interestingly, these nanosheets tend to transform into a hydrogel without the need of any additives. We found that the degree of gelation depends on the ratio of TiB₂ to H₂O₂, which can be tuned to achieve gels with a shear modulus of 0.35 kPa. We also show this aqueous dispersion of nanosheets is processable and forms hierarchical paper-like macrostructures upon vacuum filtration. Such an ability to assemble into free-standing 3D structures would enable a leap to practical applications. We also show that the high surface area and presence of oxy-functional groups on these nanosheets endow them a superior photocatalytic activity to degrade organic pollutants. This exemplifies the rich potential that TiB₂ offers upon nanoscaling. The results presented here not only add a novel material to the 2D flatland but also urge the scientific community to revisit the chemistry of metal borides, that have been traditionally considered as relatively inert ceramics.

Synthesis of a novel polysuccinimide based resin for the ultrahigh removal of anionic azo dyes from aqueous solution

A novel hyper-cross-linked polyamide resin (PSI-PA) has been synthesized for the ultrahigh removal of Congo red (CR) and Eriochrom Black T (EBT) from aqueous solution. The mesoporous resin, having a specific surface area (98.80 m² g^-1), showed maximum adsorption capacity (Q_max) of 522.18 mg g^-1 for CR (pH 9.0) and 460.34 mg g^-1 for EBT (pH 6) at room temperature. The adsorption of these dyes was rapid and the equilibrium was attained within 4 h. The kinetic data was well-fitted by pseudo-second-order rate equation. Analysis of the surface chemical composition of loaded PSI-PA by XPS revealed the appearance of a new peak at around 166.0 eV (S 2p), confirming the adsorption of the sulfur-based dyes onto the resin. Examination of experimental data of dyes adsorption by a variety of non-linear adsorption isotherms and kinetic models suggested that the Langmuir model exhibited the best fit with high correlation coefficients for both CR (R² = 0.9966) and EBT (R² = 0.9934). PSI-PA has been extensively characterized by FT-IR, solid state ¹³C (CP-MAS) NMR, EDS, TGA and BET analysis. Moreover, PSI-PA exhibited 82% removal efficiency for dyes in simulated effluents, manifesting its promise and utility for treating industrial effluent.

Removal of gentian violet and rhodamine B using banyan aerial roots after modification and mechanism studies of differential adsorption behaviors

A novel adsorbent derived from banyan aerial roots was prepared via modification and employed to aqueous gentian violet (GV) and rhodamine B (RhB) removal. The surface morphology and physicochemical properties of modified banyan aerial roots (MBARs) were investigated by SEM, EDS, N₂ adsorption/desorption, zeta potential, XRD, and FT-IR characterization experiments. Adsorption factors were tested, and the optimal conditions for GV and RhB removal were pH of 6 and 3, doses of 0.02 g and 0.03 g, and reaction time of 540 min. Adsorption isotherm simulation illustrated that theoretical monolayer adsorption capacities of GV and RhB were 456.64 mg/g and 115.23 mg/g, respectively. Kinetics data was assessed with pseudo-first-order and pseudo-second-order models, and the latter described GV and RhB adsorption better at 288 K, 298 K, 308 K, and 318 K. Thermodynamic analysis indicated that GV and RhB adsorption processes were endothermic and spontaneous. From the research results, it could be inferred that GV adsorption was mainly dominated by electrostatic interaction, while RhB adsorption might be primarily attributed to electrostatic interaction and hydrogen bonding. The study based on full utilization of waste plant fibers facilitates recycling of biomass resources, and due to simplicity, safety, and eco-friendliness of the preparation, as well as low cost and high efficiency of the application, MBARs may be potential absorbents for the treatment of dyestuff wastewater.

Correction to the calculation of Polanyi potential from Dubinnin-Rudushkevich equation

The Dubinin-Radushkevitch (D-R) adsorption isotherm model has been widely used to measure adsorption, and it can be used to value the mean free adsorption energy (E). In order to do this, the first step is to calculate the Polanyi adsorption potential (Ɛ). However, we find that the computational formula of Polanyi potential from the D-R equation has a dimensinal problem. Specifically, the units of the equilibrium concentration of solute (C_e) used in the Polanyi potential equation are in chaos. Accurate calculation is the basic characteristic of scientific papers. This comment highlighted the possible flaws related to the calculation of Polanyi potential and analyzed the evolution and application of Polanyi potential equation, and then provided the modified form of Polanyi potential equation. This note offers deeper insights into the Polanyi potential equation, and can help avoid misuse and propagation of the Polanyi potential equation in adsorption research.

Synergistic Catalysis of Co(OH)2/CuO for the Degradation of Organic Pollutant Under Visible Light Irradiation

The exploration of advanced water treatment technologies e.g. heterogeneous photocatalysis is the most promising way to address organic pollution issues. Semiconductors based bimetallic photocatalysis with wide bandgap, have displayed splendid degradation performance in the UV light region, but their extension to the visible light/near infra-red region is still a matter of great concern. CuO, Co(OH)₂, CoO and Co(OH)₂/CuO nanocomposites were synthesized via simple co-precipitation method and further practiced for Rhodamine B (RhB) decomposition by introducing per-sulfate (PS) as a sacrificial agent. Results revealed that Co(OH)₂/CuO catalyst had shown robust catalytic activity for RhB photodegradation (degradation time 8 min, k = 0.864 min⁻¹) under light illumination, significantly less (12–60 times) than the other reported bimetallic catalysts. Catalyst also have verified excellent performance for a broader pH range (5–9) with excellent stability. Main reactive species responsible for the photocatalytic reaction were sulfate (SO₄^•−) and superoxide (O₂^•) radicals, duly verified by ESR and by using radical scavengers. With outstanding recycling abilities, this is probably the fewer successful attempt for RhB decolorization and can be highly favorable for effluent treatment by using the synergic effect of absorption and photodegradation.

Brief bibliometric analysis of "ionic liquid" applications and its review as a substitute for common adsorbent modifier for the adsorption of organic pollutants

The importance of improving adsorbent's adsorption efficiency in organic pollutants has been reported by many researchers. Surfactant-based modified adsorbents were a tasteful choice. As a result, the use of surfactants as a modifier for removing organic pollutants has shown to play a very big role in enhancing the adsorption efficiency of different materials. Ionic liquids are receiving extensive interest as green multipurpose compounds, primarily as a replacement for traditional chemicals that are used in many chemical processes. This work gives a brief bibliometric analysis of application of ionic liquid from 1930 to 2017, documents were collected from Scopus database and keywords from the abstracts and titles were analyzed using VOSviewer software. Furthermore, the work presents a review of conventionally known surfactants and the recent likelihood of ionic liquids for modifying adsorbents for adsorption of organic pollutants. Over the period of years between 1930 and 2017, 13,144 documents were published on the application of ionic liquids. VOSviewer software further confirms that adsorption is one of the leading areas in applications of ionic liquids. Review also showed that ionic liquid is a good modifier of adsorbents.