Biomass-derived versatile activated carbon removes both heavy metals and dye molecules from wastewater with near-unity efficiency: Mechanism and kinetics

Groundnut-shell derived oxygen enriched mesoporous carbon adsorbent for removal of thiophenic sulfur compounds

In this work, groundnut shell-derived mesoporous carbons, synthesized by one-step carbonization at different temperatures in presence of potassium hydroxide, were used for desulfurization studies involving dibenzothiophene, benzothiophene and thiophene. The pore formation and corresponding surface area of synthesized mesoporous carbon was governed by carbonization temperature as it increased from 600 to 900 °C. The carbon synthesized at carbonization temperature of 800 °C, that is GN-800, showed highest surface area (1192 m2/g) and pore volume (0.58 cm3/g) amongst the all synthesized mesoporous carbons. For all the thiophenic sulfur compounds, the prepared mesoporous carbons exhibited improved adsorptive desulfurization performance as the adsorption temperature increased from 25 to 70 °C. The oxygen enriched adsorbents showed higher oxygen content and improved removal for all the thiophenic sulfur compounds. The oxygen enriched adsorbent, obtained by treatment with nitric acid (V) and carbonized at 800 °C, showed highest adsorptive desulfurization performance for all sulfur compounds. At 70 °C the removal for thiophene, benzothiophene and dibenzothiophene was 97.7, 93.8 and 90.2%, while the corresponding adsorption capacities were 58.7, 56.3 and 54.6 mg/g, respectively. For mesoporous carbonized carbons, the π-π interaction also contributed to adsorptive forces in addition to Van der Waals forces. For the oxygen enriched samples, additional acid-base interactions also contributed to adsorptive forces. The experimental data was best fitted to pseudo-second order kinetics model and Langmuir isotherm model. The adsorbent showed a slight drop in the removal percentage after five adsorption-regeneration cycles. The oxygen enriched groundnut shell derived mesoporous carbon was observed to have the potential to function as an excellent desulfurization adsorbent for producing clean fuel.

Efficient adsorption of lead and copper from water by modification of sand filter with a green plant-based adsorbent: Adsorption kinetics and regeneration

In this study, pomegranate seed waste (PSW) was added into sand filter (SF) to increase removal efficiency of Lead (Pb(II)) and Copper (Cu(II)) from polluted water. The performance of PSW was compared with activated carbon (AC) as a typical adsorbent. Based on the SEM, EDX, FTIR, XRD, BET and proximate analyses, PSW had porous structure with specific surface area of 2.76 m2/g and active compounds which suggested PSW as an appropriate adsorbent for heavy metals (HMs) adsorption. According to the batch experiments, SF without treatment could only remove 46% and 35% of Pb(II) and Cu(II), respectively. These numbers increased to 88% and 75% for Pb(II) and Cu(II) by adding 3 g/kg PSW to the SF, respectively under the optimal conditions of HMs initial concentrations = 100 mg/L, pH = 7 and contact time = 60 min. The adsorption kinetic and isotherm followed the pseudo-first-order and Langmuir models, respectively indicating that mainly physisorption was involved in the HMs adsorption process of PSW. Based on the column experiments (flow rate = 62.5 mL/min), the Pb(II) and Cu(II) removal increased from 14% to 60% and 10%-55%, respectively after 5 pore volumes (40 min) by adding 3 g/kg PSW to the SF. Breakthrough curves matched better with Thomas mode rather than Adam's Bohart proving Langmuir adsorption isotherm. Our finding suggested modification of SF with PSW is a promising approach for efficient removal of HMs from water.

Waste paper-derived porous carbon via microwave-assisted activation for energy storage and water purification

The reuse of waste papers by conversion into valuable carbon materials has received considerable attention for diverse applications such as energy storage and water purification. However, traditional methods for converting waste papers into materials with suitable properties for specific applications are often complex and ineffective, involving consecutive carbonization and activation steps. Herein, we propose a simple one-step microwave (MW)-assisted synthesis for preparing waste paper-derived porous carbons (WPCs) for energy storage and water purification. Through a 30-min synthesis, WPCs with graphitic structure and high specific surface area were successfully produced. The fabricated WPCs exhibited outstanding charge storage capability with a maximum specific capacitance of 237.7 F g-1. Additionally, the WPC demonstrates a high removal efficiency for various dyes, achieving a maximum removal efficiency of 95.0% for methylene blue. The developed one-step MW synthesis not only enables the production of porous carbon from waste paper, but also offers a viable approach to address solid waste management challenges while simultaneously yielding valuable materials.

Adsorption of Pb (II) ions on variable charge oxidic calcined substrates with chemically modified surface

Background

The paper describes lead ion adsorption on variable charge oxidic calcined substrates with chemically modified surfaces. Amphoteric oxides of iron, aluminum, titanium, and manganese, change their surface electric charge after acid or alkaline treatment, letting cationic or anionic adsorption reactions from aqueous solutions. This property allows using them as adsorbing substrate for heavy metals retention in water treatment systems.

Methods

Substrate was prepared by extruding cylindrical strips from a saturate paste of the oxidic lithological material-OLM; dries it up and thermally treated by calcination. The study was performed by triplicated trial, on batch mode, using 2 grams samples of treated with NaOH 0.1N and non-treated substrate. Lead analysis was performed by AAS-GF. Freundlich and Langmuir models were used to fit results. Comparing differential behavior between treated and non-treated substrates showed the variable charge nature of the OLM.

Results

Results show L-type isotherms for the adsorption of Pb(II) ions on the activated substrate, suggesting good affinity between Pb(II) ions and OLM's surface. Average value of adsorption capacity ( K) for activated substrate (1791.73±13.06), is around four times greater than the non-activated substrate (491.54±31.97), during the adsorption reaction, 0.35 and 0.26 mmolH + of proton are produced on the activated and non-activated substrate respectively using a 1 mM Pb(II) solution and 72.2 and 15.6 mmolH + using a 10 mM Pb(II) solution. This acidification agrees with the theoretic model of transitional metals chemisorption on amphoteric oxides, present in lithological material used for the preparation of adsorbent substrates, confirming the information given by the L-type isotherms.

Conclusions

Results suggest that these variable charge oxidic adsorbent substrate show great potential as an alternative technique for water treatment at small and medium scale using granular filtration system. The easiness and low price make them suitable to apply in rural media where no treating water systems is available.

Selective adsorption of single and binary dyestuffs by citrus peel: Characterization, and adsorption performance

The powdered citrus peel, which has been replaced with sodium hydroxide, was used in this study to test how well methylene blue and reactive black 5 dyestuff absorbed one or both. To find out about the texture and surface chemistry of modified citrus peel, Fourier transform infrared spectroscopy and scanning electron microscope analyses were carried out. Fourier transform infrared spectroscopy data revealed the presence of amphoteric radicals on the modified citrus peel surface, indicating the effective adsorption of methylene blue and reactive black 5. Many parameters affecting the batch adsorption process, such as modified citrus peel dose (0.1-0.5 g), pH (2-10), time (20-80 min), stirring speed (60-180 rpm), and temperature (20-45 °C), were studied. It is seen that the physical effect is at the forefront, homogeneous monolayer adsorption occurs, and the process fits the Langmuir and pseudo first order models for dyestuffs. Thermodynamic modeling showed that the adsorption of methylene blue and reactive black 5 was spontaneous and endothermic. At pH 2, an adsorption capacity of 0.67 mg/g and a removal efficiency of 66.86% were achieved for reactive black 5. For methylene blue at pH 6, the adsorption capacity was 4.34 mg/g, and the decolorization rate was 87%. The decreases in the removal rates of dyestuffs in the binary system indicate that they are affected by their simultaneous presence in the solution. The results proved that modified citrus peel can be useful for dyestuff removal in single or binary systems, although the removal capacity of modified citrus peel is highly dependent on methylene blue and reactive black 5.

Utilization of bagasse fly ash for the production of low-cost ammonia adsorbents in poultry farm

NH3 pollution is a significant problem in the poultry farming because excess NH3 can negatively impact chicken health and stunt their growth. Therefore, this study investigated the low-cost production of bagasse fly ash (FA)-a byproduct of the sugar industry-as an NH3 adsorbent. Hydrothermal carbonization and activation were applied to enhance NH3 adsorption using FA. In the experiments, the adsorption capabilities were improved using industrial waste materials mixed with bamboo char or red mud. The experimental results indicate that bagasse FA mixed with bamboo hydrochar under 10 % loading achieved an NH3 adsorption capacity of ∼ 1.02 mg-NH3/g-adsorbent, or ∼ 55 % of that of the commercial adsorbent. To avoid secondary pollution and provide the spent absorbents with an added value, their use in CO2 capture applications was evaluated. The results showed that the adsorbent had a 0.28 mmol-CO2/g-adsorbent capacity.

Adsorption of heavy metal onto biomass-derived activated carbon: review

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Review on Liquid-Liquid Separation by Membrane Filtration

Liquid-liquid separation is crucial in the present circumstances. Substitution of the conventional types of separation like distillation and pervaporation is mandatory due to the high energy requirement of the two. The separation of organic mixtures has a huge potential in industries such as pharmaceutical, fine chemicals, fuels, textile, papers, and fertilizers. Membrane-affiliated separations are one of the prime techniques for liquid-liquid separations. Organic solvent nanofiltration, solvent-resistant nanofiltration, and ultrafiltration are a few methods through which organic liquid-liquid separation can be attained. Implementation of such a technology in chemical industries reduces the time consumption and is cost efficient. Even though a lot of research has been done, attention is needed in the field of organic-liquid separation aided by membranes. In this review, various membranes used for organic mixture separations such as polar-nonpolar, polar-polar, and nonpolar-nonpolar are discussed with a focus on membrane materials, additives, separation theory, separation type, experimental setup, fouling mitigation, surface modification, and major challenges. The review also offers insights and probable solutions for existing problems and also discusses the scope of research to be undertaken in the future.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Insights into the mechanically resilient, well-balanced polymeric membranes by incorporating Rhizophora mucronata derived activated carbon for sustainable wastewater decontamination

In this study, hydrophilic activated carbon has been prepared and used to synthesize innovative activated carbon/polysulfone mixed matrix membranes (MMMs). These membranes were investigated in terms of membrane morphology, hydrophilicity, antifouling ability, and metal ions rejection. The activated carbon (AC) was prepared from a simple chemical activation method using Rhizophora mucronata propagules, which are rich in aerenchyma cells and possess a high surface area. The hydrophilicity of the MMMs is enhanced by the incorporation of activated carbon, which is confirmed by the measurement of equilibrium water contact angle, water uptake and pure water flux. The optimized concentration of 0.625 wt% activated carbon (A₂) incorporated mixed matrix membrane exhibits better rejection efficiencies of 98 ± 0.5%, 99 ± 0.5%, 92 ± 2%, and 44 ± 1% for Pb⁺², Cd⁺², Hg⁺², and F^- with the permeate flux of 28.27, 31.88, 33.21, 43.82 L/m²/h, respectively. The fabricated mixed matrix membranes demonstrated an excellent flux recovery ratio and reversible fouling, when filtrating a mixed feed solution containing 200 ppm BSA, 10 ppm Pb⁺² and 10 ppm Cd⁺². The optimized A₂ membrane showed excellent long-term stability up to 120 h without compromising in permeate flux and rejection efficiency. Finally, a numerical investigation using a usual transport model has shown that dielectric exclusion was the most probable mechanism that can physically explain experimental trends.

Effective adsorption of crystal violet onto aromatic polyimides: Kinetics and isotherm studies

The motive of this work is to synthesis aromatic polyimides by a two-step poly condensation process and the prepared aromatic polyamides (APIs) is been used as an effective functionalized adsorbent for the removal of carcinogenic crystal violet (CV) from aqueous medium. The adsorption efficiency of the APIs was enhanced by incorporation different functional moieties (varying aromatic dianhydrides with -O-, -(CF₃)₂-, -(CH₃)₂-) in the polymer structure. The initial and final concentration of CV was measured using UV-Vis spectrometer. The adsorption process was optimized by varying the parameters such as the effect of solution pH, contact time, initial dye concentration, and adsorbent dosage. Kinetics and isotherms of the adsorption system were appraised using data obtained from effect of contact time and initial dye concentration with corresponding empirical modelling techniques respectively. The evaluated results of the adsorption kinetic studies confirmed that the adsorption of API onto CV is followed a pseudo-second-order kinetic model. The adsorption behaviour and their interactions between APIs and CV are well established. The experimental results of this research output could be confirmed that APIs is a very effective adsorbent for the removal of cationic dye from aqueous.

Rapid and efficient adsorption of methylene blue dye from aqueous solution by hierarchically porous, activated starbons®: Mechanism and porosity dependence

Hierarchically porous activated Starbons® derived from starch are found to make excellent adsorbents for methylene blue, even in the presence of other dyes and inorganic salts, highlighting their potential to be used in water purification. The optimal material (S950C90) has a methylene blue adsorption capacity (891 mg g^-1) almost nine times higher than that of unactivated S800 and four times higher than that of commercial activated carbon at 298 K. The adsorption of methylene blue onto optimal materials (S950C90 and S800K4) reaches equilibrium within 5 min. Adsorption data for all the adsorbents show a good fit to the Freundlich isotherm which allows the Gibbs free energies of adsorption to be calculated. The adsorption capacities increase as the pH of the methylene blue solution increases, allowing the dye to be desorbed by treatment with acidic ethanol and the Starbon® materials reused. Porosimetry and SEM-EDX imaging indicate that methylene blue adsorbs throughout the surface and completely fills all the micropores in the Starbon® adsorbent. The methylene blue adsorption capacities show excellent correlations with both the BET surface areas and the micropore volumes of the materials.

Development of Eggshell-Based Orange Peel Activated Carbon Film for Synergetic Adsorption of Cadmium (II) Ion

Heavy metal contamination has spread around the world, particularly in emerging countries. This study aimed to assess the effectiveness of starch/eggshell/orange peel-activated carbon-based composite films in removing cadmium (II) ions from water samples. X-ray diffraction and scanning electron microscopy were used to characterize the composite films. The effect of Cd²⁺ was studied using a UV-Vis spectrophotometer and atomic absorption spectroscopy. The morphology of the composite film reveals a highly porous and rough surface with more open channels and a non-uniform honeycomb, indicating that the film has a high potential to adsorb Cd²⁺. The diffraction peaks for this film were found to be at 13.74°, 17.45°, 18.4°, and 23.6°, indicating a typical crystalline A-type packing arrangement within the starch granules. The results indicate that crystalline structure was unaffected by the addition of eggshell powder and orange peel-activated carbon. In 0.5 mg L^-1 and 1.0 mg L^-1 Cd²⁺ ions, the composite film removed 100% and 99.7% of the Cd²⁺, respectively, while the maximum removal efficiency for methylene blue was 93.75%. Thus, the current study shows that starch/eggshell/orange peel activated carbon film has a high potential for commercial activated carbon as a low-cost adsorbent.

Equilibrium Isotherms and Kinetic Effects during the Adsorption of Pb(II) on Titanosilicates Compared with Natural Zeolite Clinoptilolite

The present study focuses on the adsorption of Pb(II) by the H-form of titanosilicates (ETS-4, GTS-1) and clinoptilolite. The H-forms were prepared by first exchanging the extra-framework cations—Na+, K+, Ca2+, etc.—with NH4+, and by subsequent thermal treatment for obtaining H-forms. The purity and thermal behaviour of the initial, NH4+, and H-forms of ETS-4, GTS-1, and clinoptilolite were analysed by powder XRD, while the morphology and size of the particles were determined by SEM. The chemical composition of the solids and the solutions was obtained by WDXRF and ICP-OES, respectively. The kinetics research of the Pb(II) adsorption processes was based on WDXRF and ICP-OES. The H-forms of the materials displayed favourable properties for the adsorption of Pb(II). The best behaviour in this respect was demonstrated by GTS-1 when compared to ETS-4 and clinoptilolite.

Simultaneous removal of Pb2+ and direct red 31 dye from contaminated water using N-(2-hydroxyethyl)-2-oxo-2H-chromene-3-carboxamide loaded chitosan nanoparticles

This study reports the preparation of a new material that can remove synthetic dyes and trace metals simultaneously. A new coumarin derivative was synthesized and its chemical structure was inferred from spectral data (FT-IR, 1H-NMR, 13C-NMR). Meanwhile, chitosan nanoparticles (CsNPs) were prepared then used as a carrier for two different concentrations of the coumarin derivative (C1@CsNPs and C2@CsNPs). The TEM, SEM and DLS findings illustrated that the prepared nanocomposites exhibited spherical shape and small size (less than 200 nm). The performance of the prepared material for the removal of an anionic dye (direct red 31, DR31) and cationic trace metal (Pb2+) was evaluated in unary and binary systems. The results revealed that complete removal of 10 mg L-1 of DR31 and Pb2+ in unary system was achieved at pHo 3.0 and 5.5 using 0.5 and 2.0 g L-1, respectively, of C2@CsNPs. The adsorption of DR31 and Pb2+ followed different mechanisms as deduced from the effect of pHo, kinetic, isotherm and binary adsorption studies. The adsorption of DR31 followed the Langmuir isotherm model and the pseudo-first-order kinetic model. While, the adsorption of Pb2+ followed Freundlich isotherm model and Elovich kinetic model. In the binary system, the co-presence of DR31 and Pb2+ did not affect the adsorption of each other's. Overall, the prepared material showed promising results for the removal of anionic dyes and cations trace metals from contaminated water.

Waste biomass based potential bioadsorbent for lead removal from simulated wastewater

Present study deals with the lead removal from simulated wastewater using cost effective bio-adsorbent of mango seeds cover with kernel (M), and jamun seeds cover with kernel (JP). Lead removal optimization of adsorption parameters has been analyzed by using Response surface methodology (RSM). The optimum adsorption was attained at speed of 500 rpm, 60 mg, pH 6.5 and contact time of 120 min. The adsorption capacities are around 39.15 mg/g of M and 20.28 mg/g of JP bio-adsorbent, and also the maximum Pb removal were observed ̴ 94.85% and 92.78%, respectively. The regression coefficient was best fitted for both bio-adsorbents are Freundlich model and pseudo-first order reaction kinetic.

Zein adsorbents with micro/nanofibrous membrane structure for removal of oils, organic dyes, and heavy metal ions in aqueous solution

Developing multi-functional media for effectively removing different contaminants coexisted in wastewater system is highly desired. Herein, zein, a natural protein possessing abundant functional groups in molecule, is chosen to be fabricated into micro/nanofibrous membranes as adsorbents and separation media. Zein fibers with novel groove ribbon structures, which possess better structural characteristics, are designed for obtaining good adsorption performance. The adsorption performances of zein fiber membranes are evaluated. The results show that zein fiber membranes have the adsorption capacities up to 94 g/g for motor oil, 168 mg/g for Congo red, and 189 mg/g for Pb²⁺ ion for 1000 mg/L initial solution concentration, showing considerable competitiveness as compared with the reported adsorbents. The zein membrane with groove ribbon fiber morphology exhibits optimal adsorption capability and can be attractive multi-functional separation media.