Superior adsorption and removal of doxorubicin from aqueous solution using activated carbon via thermally treated green adsorbent: isothermal, kinetic, and thermodynamic studies

Activated carbon from apricot seeds (ASAC) was successfully made using a low-cost, straightforward synthesis process. With the use of various instruments, including XRD, XPS, FT-IR, SEM, and TEM, the adsorbent was demonstrated. The surface area of the ASAC that was given was also shown to be 436.8 m2/g. It was discovered that the synthesized ASAC has a fantastic capacity to absorb the anti-cancer medication doxorubicin hydrochloride (DOX). Based on changes in temperature, pH, and DOX concentration, The DOX adsorption behaviour's mechanism was evaluated. The adsorption capacity of ASAC for DOX was greater at pH 6.0, according to experimental data as the adsorption capacity was discovered to be 951.13 mg/g. Adsorption equilibrium analysis revealed that, when compared to the other models, the Langmuir adsorption provided the best fit to the data that were collected. Additionally, The ASAC has validated the DOX activation energy of adsorption as a chemisorption technique. The kinetics of adsorption were shown to be fitted to pseudo-second-order kinetic model. The reaction was endothermic and spontaneous, according to thermodynamic data. Innvestigation the removal efficiency of ASAC to remove DOX from real watrer sample (tap water, effluent wastewater, and impact wastewater). It was suggested by the results that ASAC was a viable option for treating wastewater and adsorbing DOX. The synthesized ASAC has noteworthy cyclability and reusability characteristics due to its high efficiency (up to five cycles) and low cost (around 86 percent).

Amoxicillin removal from water by adsorption on activated carbon of mineral sources: discussion of experimental data, mechanisms and modeling

The use of antibiotics has increased considerably in the last decades in human medicine, as well as agriculture and animal production. Consequently, high loads of these emerging contaminants in the environment can increase antibiotic-resistant genes and the development of multi-resistant pathogenic microorganisms. This work aims to evaluate the removal of amoxicillin trihydrate in aqueous medium using mineral-activated carbon of bituminous origin as an adsorbent. The adsorbent was classified as microporous with associated mesopores, showing phenolic groups on its surface, which indicates the versatility of the adsorbent. The adsorption kinetics and isotherms were predominantly chemical. Pseudo-second-order model, as well as LDF model adjusted to the kinetic data. Sips and Langmuir isotherms adjusted to the adsorption equilibrium data. The maximum adsorptive capacity obtained experimentally was 313.30 mg g-1 at 50°C. The thermodynamic properties suggested spontaneous, monolayer, and endothermic adsorption. Overall, compared to previous works, the adsorbent proved to be a viable and promising alternative for the removal of antibiotics from water, with high adsorption capacity of amoxicillin, without being necessary to perform any prior changes to the material.

Modification of natural zeolite clinoptilolite and ITS application in the adsorption of herbicides

The clinoptilolite natural zeolites (NZs) posses low herbicide adsorption capacity demanding acid-, alkali-, or salt chemical modifications that enhance its adsorption. However, this may affect the material structure and charge distribution. Alternatively, zeolites may be synthesized at a high cost and time-consuming process. Consequently, new methods, such as the hydrothermal method, for NZ modification needs to be studied. In this sense, a novel surface-modified zeolite (SMZ), using hexadecyltrimethylammonium bromide (CTAB), in acid media was produced by the hydrothermal method and applied for the adsorption of Atrazine (ATZ), Diuron (DIU) and 2,4-D. Commercial NZ and SMZ were characterized by SEM, XRD, TGA, FT-IR, AA spectroscopy, pHPZC, Zeta potential and N2-physisorption. The SMZ chosen for the adsorption experiments was the one with the highest modification yield and adsorption capacity obtained from a complete design of experiments (CTAB=0.74 ; D=12 Mesh; HCl=0.1 M; t=6 h and T=205 ºC). The adsorption experiments revealed that the SMZ adsorption capacity for the herbicide 2,4-D (qmax=9.02 mg/g) was greater than that obtained for ATZ (qmax=2.11 mg/g) and DIU (qmax=1.85 mg/g), which was explained by the presence of the hydroxyl group and by geometric characteristics of the 2,4-D. Adsorption models' fitting showed that the adsorption of 2,4-D onto SMZ were best described by pseudo-second order kinetic (k2=0.005-0.006 g/mg.min; qe,exp=7.122-8.614 mg/g) and Langmuir isothermal model (KL=0.283-0.499 L/mg; qm=7.167-7.995 mg/g). These results indicate that the hydrothermal method is a viable alternative to enable the use of NZs for the adsorption of emerging contaminants from wastewater.

Intensification of thorium biosorption onto protonated orange peel using the response surface methodology

In this research work, intensifying the possibility of protonated orange peel to uptake thorium (IV) ions from aqueous solutions in a batch system was investigated and optimized using the response surface methodology. The effect of three independent process variables including thorium initial concentration, pH, and biosorbent dosage was assessed based on the central composite design. The validity of the quadratic model was verified by the coefficient of determination. The optimization results showed that the rate of thorium (IV) uptake under optimal conditions is 183.95 mg/g. The modeling results showed that the experimental data of thorium biosorption kinetics are fitted well by the pseudo-second-order model. According to the results, the biosorption process reached equilibrium after around 4 h of contact. The Langmuir isotherm describes the experimental biosorption equilibrium data well. The maximum absorption capacity of protonated orange peel for thorium adsorption was estimated by the Langmuir isotherm at 236.97 mg/g. Thermodynamic studies show that thorium adsorption on protonated orange peel is thermodynamically feasible, spontaneous, and endothermic.

Adsorptive Removal of Rhodamine B Dye Using Carbon Graphite/CNT Composites as Adsorbents: Kinetics, Isotherms and Thermodynamic Study

The study of the adsorption efficiency of new carbon/CNT composites was undertaken to remove a cationic dye, Rhodamine B (RhB), from dye-contaminated wastewater. Indeed, we investigated the effect of different experimental parameters such as time, initial concentration of dye and temperature on the adsorption of RhB by the carbon composites (KS44-0 and KS44-20). The results showed that the adsorption uptake increased with the initial concentration and solution temperature while maintaining a relatively constant pH. The presence of the carbon nanotubes provided more active sites for dye removal and improved the adsorption behavior of Rhodamine B dye. The analysis of the experimental data was conducted using model equations, such as Langmuir, Freundlich and Temkin isotherms. As regards the Freundlich isotherm model, it was the best fit for the equilibrium data obtained from the experiments. The applicability of the pseudo-second-order equation could be explained assuming that the overall adsorption rate is limited by the rate of adsorbate transport that occurs on the pore surfaces of adsorbents. Furthermore, the intraparticle diffusion and Bangham models were used to investigate the diffusion mechanism of RhB absorption onto carbon composites. They showed that multiple adsorption stages occurred simultaneously via pore surface diffusion. Concerning the thermodynamic parameters (∆G°, ∆H°, and ∆S°), they were calculated and explained in the mean of the chemical structure of the adsorbate. Negative standard Gibbs free energy change values (ΔG°_ads) at all temperatures suggested that the adsorption process was spontaneous, and the positive values of the standard enthalpy change of adsorption (∆H°_ads) revealed the reaction to be endothermic. The values of standard enthalpy (ΔH°_ads) and activation energy (E_a) indicated that the adsorption process corresponds to physical sorption. The mechanisms for the removal of Rhodamine B dye from wastewater using carbon composite were predicted. RhB is a planar molecule that is readily adsorbed, in which adsorbed molecules are bound by hydrophobic or other weak interactions due to the π-π interactions between the dyes' aromatic backbones and the hexagonal skeleton of graphite and carbon nanotubes. Thus, the graphite carbon/carbon nanotube composite is believed to play a major role in organic pollutant reduction.

Elevated Adsorption of Lead and Arsenic over Silver Nanoparticles Deposited on Poly(amidoamine) Grafted Carbon Nanotubes

An efficient adsorbent, CNTs-PAMAM-Ag, was prepared by grafting fourth-generation aromatic poly(amidoamine) (PAMAM) to carbon nanotubes (CNTs) and successive deposition of Ag nanoparticles. The FT-IR, XRD, TEM and XPS results confirmed the successful grafting of PAMAM onto CNTs and deposition of Ag nanoparticles. The absorption efficiency of CNTs-PAMAM-Ag was evaluated by estimating the adsorption of two toxic contaminants in water, viz., Pb(II) and As(III). Using CNTs-PAMAM-Ag, about 99 and 76% of Pb(II) and As(III) adsorption, respectively, were attained within 15 min. The controlling mechanisms for Pb(II) and As(III) adsorption dynamics were revealed by applying pseudo-first and second-order kinetic models. The pseudo-second-order kinetic model followed the adsorption of Pb(II) and As(III). Therefore, the incidence of chemisorption through sharing or exchanging electrons between Pb(II) or As(III) ions and CNTs-PAMAM-Ag could be the rate-controlling step in the adsorption process. Further, the Weber-Morris intraparticle pore diffusion model was employed to find the reaction pathways and the rate-controlling step in the adsorption. It revealed that intraparticle diffusion was not a rate-controlling step in the adsorption of Pb(II) and As(III); instead, it was controlled by both intraparticle diffusion and the boundary layer effect. The adsorption equilibrium was evaluated using the Langmuir, Freundlich, and Temkin isotherm models. The kinetic data of Pb(II) and As(III) adsorption was adequately fitted to the Langmuir isotherm model compared to the Freundlich and Temkin models.

Adsorption characteristics of N-rGO for multiple representative trace antibiotics in water

Antibiotics have attracted considerable attention as pollutants; however, they have not been controlled because they cannot be effectively treated via conventional water treatment. In this study, nitrogen-doped reduced graphene oxide (N-rGO) was prepared, and its adsorption performance on multiple trace antibiotics in water was investigated by considering sulfamethoxazole, levofloxacin, clindamycin, tetracycline, penicillin, and chloramphenicol as target pollutants. The results demonstrated that the adsorption process was completed within 60 min at a removal rate exceeding 80%. The adsorption process was in line with the first-order kinetic equation and the Langmuir isothermal adsorption model, with a theoretical maximum adsorption capacity of 1,265.82 mg g^-1 . Meanwhile, the effect of pH value was related to the structure of antibiotics. Simulation studies showed that anions and cations in natural water matrix did not inhibit the adsorption process, whereas humic acid adversely affected the adsorption effect. Characterizations revealed that the N-rGO surface was wrinkled with abundant and diverse oxygen-containing functional groups, which provided suitable conditions for efficient adsorption. The results indicated that N-rGO rapidly and effectively adsorbed trace antibiotics in water, thus providing a basis for constructing an adsorption-catalytic oxidation system. Overall, the proposed method is excellent for treating trace antibiotics in a water environment.

Removal of phosphorus in wastewater by sinusoidal alternating current coagulation: performance and mechanism

The effects of initial total phosphorus (TP) concentration, current density, conductivity and initial pH value on the removal rate of TP and energy consumption, as well as the behaviour and mechanism of phosphorus removal, were investigated by sinusoidal alternating current coagulation (SACC). The flocs produced by SACC were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy FTIR and X-ray photo electron spectroscopy. The thermodynamic and kinetic behaviours of phosphorus removal by iron sol adsorption were also studied in detail. In a self-made SACC reactor equipped with five sets of parallel iron electrodes spacing 10 mm, the removal rate of TP reached 90.9% for a pH 7.0 wastewater with 5 mg dm^-3 TP (κ = 800 μS cm^-1) after being treated for 60 min by applying 2.12 mA cm^-2 sinusoidal alternating current. Compared with direct current coagulation (DCC), SACC exhibits a higher removal efficiency of phosphorus due to the stronger adsorption of the produced flocs. It was found that the adsorption in the SACC process follows pseudo-second-order kinetic with the involvement of the intra-particle model. The adsorption of iron sol to phosphorus was an endothermic and spontaneous process, and its adsorption behaviour can be characterized with Langmuir and Redlich-Peterson isothermal adsorption models. SACC may be employed for the treatment of more complex wastewater combined with biological and/or electrochemical techniques.

Removal of inorganic pollutants using electrocoagulation technology: A review of emerging applications and mechanisms

Electrocoagulation (ECoag) technique has shown considerable potential as an effective method in separating different types of pollutants (including inorganic pollutants) from various sources of water at a lower cost, and that is environmentally friendly. The EC method's performance depends on several significant parameters, including current density, reactor geometry, pH, operation time, the gap between electrodes, and agitation speed. There are some challenges related to the ECoag technique, for example, energy consumption, and electrode passivation as well as its implementation at a larger scale. This review highlights the recent studies published about ECoag capacity to remove inorganic pollutants (including salts), the emerging reactors, and the effect of reactor geometry designs. In addition, this paper highlights the integration of the ECoag technique with other advanced technologies such as microwave and ultrasonic to achieve higher removal efficiencies. This paper also presents a critical discussion of the major and minor reactions of the electrocoagulation technique with several significant operational parameters, emerging designs of the ECoag cell, operating conditions, and techno-economic analysis. Our review concluded that optimizing the operating parameters significantly enhanced the efficiency of the ECoag technique and reduced overall operating costs. Electrodes geometry has been recommended to minimize the passivation phenomenon, promote the conductivity of the cell, and reduce energy consumption. In this review, several challenges and gaps were identified, and insights for future development were discussed. We recommend that future studies investigate the effect of other emerging parameters like perforated and ball electrodes on the ECoag technique.

Scalable synthesis of monodisperse and recyclable sulphonated polystyrene microspheres for sustainable elimination of heavy metals in wastewater

Herein, we demonstrate a scalable method for fabricating monodisperse sulphonated polystyrene (SPS) microspheres with abundant sulphonic acid groups and excellent heavy metal removal ability. A comprehensive characterization through SEM, EDS, FT-IR, TG, XRD and XPS confirmed the formation of the SPS microspheres. Take advantage of the abundant sulphonic acid groups on the surface of microspheres, as well as the superior monodisperse properties, adsorption ability of SPS microspheres both in quantity and speed have been enhanced. The adsorption equilibrium obeyed the Langmuir isotherm model with the theoretical maximum capacities of 49.16, 15.38 and 13.89 mg·g-1 for Pb2+, Zn2+ and Cu2+, respectively (30°C, pH = 3.5). Besides, the adsorption equilibriums of Pb2+ onto SPS microspheres can be achieved within only 1 min and the adsorption kinetics can be fitted by a pseudo-second-order kinetics model. More importantly, because of the micron structure of the SPS microspheres, it could overcome the excessive hydrophilia brought by rich sulphonic acid groups and thereby easily separated, which maintain a good recyclable capacity after five regeneration cycles. With the excellent adsorption ability and reusability, SPS microspheres can efficiently handle the polluted water in a convenience and rapid process, which satisfies the sustainable pollution treatment in heavy metals elimination.

A critical review on recent developments in MOF adsorbents for the elimination of toxic heavy metals from aqueous solutions

Effective and substantial remediation of contaminants especially heavy metals from water is still a big challenge in terms of both environmental and biological perspectives because of their adverse effects on the human health. Many techniques including adsorption, ion exchange, co-precipitation, chemical reduction, ultrafiltration, etc. are reported for eliminating heavy metal ions from the water. However, adsorption has preferred because of its simple and easy handlings. Several types of adsorbents are observed and documented well for the purpose. Recently, highly porous metal-organic frameworks (MOFs) were developed by incorporating metals and organic ligands together and claimed as potent adsorbents for the remediation of highly toxic heavy metals from the aqueous solutions due to their unique features like greater surface area, high chemical stability, green and reuse material, etc. In this review, the authors discussed systematically some recent developments about secure MOFs to eliminate the toxic metals such as arsenic (both arsenite and arsenate), chromium(VI), cadmium (Cd), mercury (Hg) and lead (Pb). MOFs are observed as the most efficient adsorbents with greater selectivity as well as high adsorption capacity for metallic contamination. Graphical abstract.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state ¹³C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m² g^-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R² values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. q_M parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g^-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

Adsorption Study for the Removal of Nitrate from Water Using Local Clay

Our research aimed at the removal of nitrate ions through adsorption by local clay. A series of batch experiments were conducted to examine the effects of contact time, adsorbent characteristics, initial concentration of nitrate, pH of the solution, concentration, and granulometry of adsorbent. Adsorption isotherms studies indicated that local clay satisfies Freundlich's model. The rate of reaction follows pseudo-second-order kinetics. Local clay successfully adsorbs nitrates at pH acid. The adsorption capacity under optimal conditions was found to be 5.1 mg/g. The adsorption yield increases with adsorbent dose and decrease with initial concentration of nitrate. The local clay was characterized by the X-ray fluorescence method (XRF), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning electronics microscopy (SEM), and measurement of specific surface area (BET). The results of the study indicated that local clay is useful materials for the removal of nitrates from aqueous solutions which can be used in water treatment without any chemical modification.

A critical review on arsenic removal from water using iron-based adsorbents

Intensive research efforts have been pursued to remove arsenic (As) contamination from water with an intention to provide potable water to millions of people living in different countries. Recent studies have revealed that iron-based adsorbents, which are non-toxic, low cost, and easily accessible in large quantities, offer promising results for arsenic removal from water. This review is focused on the removal of arsenic from water using iron-based materials such as iron-based nanoparticles, iron-based layered double hydroxides (LDHs), zero-valent iron (ZVI), iron-doped activated carbon, iron-doped polymer/biomass materials, iron-doped inorganic minerals, and iron-containing combined metal oxides. This review also discusses readily available low-cost adsorbents such as natural cellulose materials, bio-wastes, and soils enriched with iron. Details on mathematical models dealing with adsorption, including thermodynamics, kinetics, and mass transfer process, are also discussed. For elucidating the adsorption mechanisms of specific adsorption of arsenic on the iron-based adsorbent, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are frequently used. Overall, iron-based adsorbents offer significant potential towards developing adsorbents for arsenic removal from water.

Synthesis and characterization of anthill-eggshell composite adsorbent for removal of hexavalent chromium from aqueous solution

In this study, adsorption behavior of anthill-eggshell composite (AEC) for the removal of hexavalent chromium (Cr⁶⁺) from aqueous solution was investigated. The raw AEC sample was thermally treated at 864 °C for 4 h and characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray fluorescence (XRF) techniques. The effects of adsorption process variables including initial Cr⁶⁺ concentration, contact time, and adsorbent dosage on the Cr⁶⁺ removal efficiency were investigated using central composite design (CCD) of response surface methodology (RSM). Equilibrium adsorption isotherm and kinetic were also studied. From the analysis of variance (ANOVA), the three variables proved to be significant and the optimum conditions for Cr⁶⁺ adsorption were obtained to be 150 mg/L initial Cr⁶⁺ concentration, 45.04-min contact time, and 0.5 g adsorbent dosage, which resulted in 86.21% of Cr⁶⁺ adsorbed. Equilibrium isotherm study showed that Freundlich model fitted well to the experimental data. The pseudo-second-order kinetic model appeared to better describe the experimental data. The study showed that mixed anthill-eggshell is a promising adsorbent for removing Cr⁶⁺ from aqueous solution.

Treatment of industrial estate wastewater by the application of electrocoagulation process using iron electrodes

In this study electrocoagulation (EC) of industrial estate wastewater taken from the inlet of wastewater treatment plant was investigated using sacrificial iron electrodes. Employing a pole changer to homogenous consumption of electrodes, studies on the parameters such as current density, supporting electrolyte concentration and initial pH, which have significant effects on COD removal and hence the energy consumption, were performed. Hydrogen peroxide was used in different concentrations to observe its effects on COD removal efficiency and the energy consumption. Sludge productions were also calculated for all experiments. COD removal efficiency of ∼92% was obtained at the best experimental conditions (i = 30 mA/cm², SE = 3 mM Na₂SO₄, pH = original pH (∼6) of the wastewater, 1500 mg/L H₂O₂) with an energy cost of €3.41/m³ wastewater treated and the sludge production of 5.45 g per g COD removed.

Selective removal of lead ions from aqueous solutions using 1,8-dihydroxyanthraquinone (DHAQ) functionalized graphene oxide; isotherm, kinetic and thermodynamic studies

The Fe₃O₄@DHAQ_GO nanocomposite can serve as an efficient adsorbent for the selective removal of lead from polluted water.

Boron removal from hydraulic fracturing wastewater by aluminum and iron coagulation: Mechanisms and limitations

One promising water management strategy during hydraulic fracturing is treatment and reuse of flowback/produced water. In particular, the saline flowback water contains many of the chemicals employed for fracking, which need to be removed before possible reuse as "frac water." This manuscript targets turbidity along with one of the additives; borate-based cross-linkers used to adjust the rheological characteristics of the frac-fluid. Alum and ferric chloride were evaluated as coagulants for clarification and boron removal from saline flowback water obtained from a well in the Eagle Ford shale. Extremely high dosages (> 9000 mg/L or 333 mM Al and 160 mM Fe) corresponding to Al/B and Fe/B mass ratios of ∼70 and molar ratios of ∼28 and 13 respectively were necessary to remove ∼80% boron. Hence, coagulation does not appear to be feasible for boron removal from high-strength waste streams. X-ray photoelectron spectroscopy revealed BO bonding on surfaces of freshly precipitated Al(OH)₃(am) and Fe(OH)₃(am) suggesting boron uptake was predominantly via ligand exchange. Attenuated total reflection-Fourier transform infrared spectroscopy provided direct evidence of inner-sphere boron complexation with surface hydroxyl groups on both amorphous aluminum and iron hydroxides. Only trigonal boron was detected on aluminum flocs since possible presence of tetrahedral boron was masked by severe AlO interferences. Both trigonal and tetrahedral conformation of boron complexes were identified on Fe(OH)₃ surfaces.

Electrocoagulation for the treatment of textile industry effluent--a review

Various techniques such as physical, chemical, biological, advanced oxidation and electrochemical are used for the treatment of industrial effluent. The commonly used conventional biological treatment processes are time consuming, need large operational area and are not effective for effluent containing toxic elements. Advanced oxidation techniques result in high treatment cost and are generally used to obtain high purity grade water. The chemical coagulation technique is slow and generates large amount of sludge. Electrocoagulation has recently attracted attention as a potential technique for treating industrial effluent due to its versatility and environmental compatibility. This technique uses direct current source between metal electrodes immersed in the effluent, which causes the dissolution of electrode plates into the effluent. The metal ions, at an appropriate pH, can form wide range of coagulated species and metal hydroxides that destabilize and aggregate particles or precipitate and adsorb the dissolved contaminants. Therefore, the objective of the present manuscript is to review the potential of electrocoagulation for the treatment of industrial effluents, mainly removal of dyes from textile effluent.