Synergic adsorption of acid blue 80 and heavy metal ions (Cu2+/Ni2+) onto activated carbon and its mechanisms

Azadirachta indica leaf extract based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon for pharmaceuticals and personal care products removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aqueous systems, posing threat to both human health and environment. In prior research, predominant focus has been on examining various adsorbents for removing PPCPs from single-pollutant systems. However, no study has delved into simultaneous adsorption of PPCPs multi-pollutant mixture. This study evaluates performance of Azadirachta indica leaf extract-based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon (ZTAC) for removing sulfadiazine (SZN) and acetaminophen (ACN). Adsorption investigations were conducted in single-component (ACN/SZN) and binary-component (ACN + SZN) systems. The synthesized ZTAC was characterized using SEM, XRD, FTIR, EDX, porosimetry and pHpzc analysis. The study examines impact of time (1-60 min), dose (0.2-4 g/L), pH (2-12) and PPCPs concentration (1-100 mg/L) on ACN and SZN removal. Various kinetic and isotherm models were employed to elucidate mechanisms involved in sorption of PPCPs. Furthermore, synergistic and antagonistic aspects of sorption process in multi-component system were investigated. ZTAC, characterized by its crystalline nature and surface area of 980.85 m2/g, exhibited maximum adsorption capacity of 47.39 mg/g for ACN and 34.01 mg/g for SZN under optimal conditions of 15 min, 3 g/L and pH 7. Langmuir isotherm and pseudo-second-order kinetic model best-fitted the experimental data indicating chemisorption mechanism. Removal of ACN and SZN on ZTAC demonstrated synergistic nature, signifying cooperative adsorption. Overall, valorization of ZTAC offers effective and efficient adsorbent for elimination of PPCPs from wastewater.

Facile synthesis and ultrastrong adsorption of a novel polyacrylamide-modified diatomite/cerium alginate hybrid aerogel for anionic dyes from aqueous environment

An eco-friendly cationic polyacrylamide (CPAM)-modified diatomite/Ce(III)-crosslinked sodium alginate hybrid aerogel (CPAM-Dia/Ce-SA) was synthesized successfully and characterized by SEM-EDS, XRD, FTIR, UV-Vis and XPS. Adsorption performance, interaction mechanism and reusability of CPAM-Dia/Ce-SA used for the removal of acid blue 113 (AB 113), acid blue 80 (AB 80), acid yellow 117 (AY 117), Congo red (CR) and Direct Green 6 (DG 6) anionic dyes from aqueous media were investigated in detail. The results demonstrate that CPAM-Dia/Ce-SA aerogel is macroscopic polymer hybrid spheres with a particle size of around 1.3 mm, unique undulating mountain-like surface and porous mesostructure, and exhibits outstanding adsorption capacity for anionic dyes and good reusability. The maximum adsorption amounts of AB 113, AB 80, AY 117, CR and DG 6 by CPAM-Dia/Ce-SA were 3008, 1208, 914, 1832 and 1232 mg/g at pH 2.0, 60 min contact time and 25 °C, and corresponding removal efficiency reached individually 97.5, 96.6, 99.7, 99.9 and 98.5 % respectively and were less affected by increasing pH up to 10.0. Dye adsorption behaviour and adsorption processes with spontaneous and exothermic nature were perfectly interpreted by the Langmuir and Pseudo-second-order rate models respectively. Physicochemical and multisite-H-bonding synergies promoted the ultrastrong biosorption of anionic dyes by CPAM-Dia/Ce-SA.

Compositional transformation of Ni2+ and Fe0 during the removal of Ni2+ by nanoscale zero-valent iron and the implications to groundwater remediation

The use of nanoscale zero-valent iron (nZVI) to remove heavy metal ions like Ni2+ from groundwater has been extensively studied; however, the compositional transformation of the Ni2+ and Fe0 during the removal is not clearly comprehensible. This study provides an insight into the componential, structural, and morphological transformations of Ni2+ and Fe0 at a solid-liquid interface using various characterization devices. The underlying mechanism of transformation was investigated along with the toxicity/impact of the transformed products on the groundwater ecosystem. The results indicated that Fe0 is transformed into lath-like lepidocrocite (γ-FeOOH), twin-crystal goethite (α-FeOOH), and spherical magnetite (Fe3O4), while Ni2+ is converted into Fe0.7Ni0.3 alloy and Fe-Ni composite (trevorite - NiFe2O4) with a fold-fan morphology. The Fe0 transformation mechanism includes the redox of Fe0 with Ni2+, H2O, and dissolved oxygen, the combination of Fe2+ and OH- produced by Fe0 corrosion to amorphous ferrihydrite, and the further mineralogical transformation to Fe oxides with the aid of Fe2+ adsorbed on ferrihydrite. The conversion of Ni2+ is accomplished by reduction by Fe0 and surface coordination with Fe oxides. Compared with Ni2+ and Fe0, the toxicity and bioavailability of the transformed products are significantly reduced, hence conducive to the application of zero-valent iron technology in groundwater remediation.

Synergic binding of rhodamine-B and heavy metal ions onto polyethyleneimine grafted freeze-dried chitosan/epichlorohydrin composite beads and possible mechanism

This paper reports a synergic binding technique of dye and cadmium/lead ions onto freeze-dried modified chitosan beads (GCCS), in this work modified chitosan beads was applied in binary solution. Chitosan beads (CS) composite was produced and polyethyleneimine was grafted onto the backbone of the developed composite. The beads were analyzed utilizing different analytical techniques such as Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The model applied in pH equilibrium was found to justify the adsorption of pollutants onto the adsorbent. The model was established from 2 equilibrium calculations, one justifying the acid-base attributes of the modified beads, the other elucidating the adsorption of the adsorbates onto the beads, and a mass balance of the various arrangement of nitrogen in the adsorbent. The excellent fit of the Pseudo-second order and intra-particle diffusion kinetic model shows that chemical binding might be the rate-limiting step. The adsorption isotherms were well represented by the Langmuir and Temkin models at a temperature of 45 °C. The maximum binding capacities (Qmax) from the Langmuir model were observed to be 390, 315 and 278 mg/g for the adsorption of dye, lead and cadmium ions respectively`. However, it was found to be higher in the binary system with the same applicable conditions. The correlation was analyzed utilizing various models and lines of best fit were obtained. Synergic effect was observed from the experimental results acquired from the adsorption of Rhodamine B (RHB) and adsorbates. These findings show the formation of fresh binding sites during simultaneous binding process.

Competitive and cooperative adsorption analysis for dye removal from multicomponent system using Prosopis juliflora activated carbon

In this study, performance evaluation of two adsorbents synthesized using invasive weed, i.e., Prosopis juliflora, was chemically activated using hydrochloric acid (HPJ) and sodium hydroxide (NPJ). The synthesized adsorbents HPJ and NPJ were subjected to SEM, EDX, XRD, FTIR, and porosimetry analysis for characterization and applied for adsorptive removal of rhodamine B (RB) and methyl orange (MO) dyes from monocomponent (MO/RB) and multicomponent (MO + RB) systems in batch mode. Meanwhile, the effect of operational parameters such as contact time, HPJ and NPJ dosage, MO/RB concentration, and [Formula: see text] on sorption of MO/RB dyes was investigated. The adsorption data was modeled through various kinetic and equilibrium models. On the other hand, the multi-dye sorption system was modeled using Langmuir competitive isotherm. Furthermore, the effect of presence of one dye on sorption of other and vice versa, i.e., competitive (antagonistic) and cooperative (synergistic) nature of sorption process, was investigated. From the results, it was observed that pseudo-second-order kinetic and Langmuir isotherm models best fit the adsorption kinetic and equilibrium data for sorption of MO and RB dyes using both HPJ and NPJ as adsorbents. Langmuir's maximum sorption ability (qm) of HPJ for sorption of MO and RB dyes was observed to be 12.77 mg/g and 9.95 mg/g, respectively, from the monocomponent system. On the other hand, qm of NPJ for sorption of MO and RB dyes was observed to be 10.51 mg/g and 8.69 mg/g, respectively. Langmuir's sorption ability (qm) was slightly higher in the MO + RB mixture in contrast to MO/RB. As a result, the sorption of MO/RB dyes from the MO + RB system showed synergistic nature. In conclusion, the HPJ and NPJ could be effectively used as sorbents for sorption of dyes from effluents.

Removal of heavy metals from binary and multicomponent adsorption systems using various adsorbents - a systematic review

The ecosystem and human health are both significantly affected by the occurrence of potentially harmful heavy metals in the aquatic environment. In general, wastewater comprises an array of heavy metals, and the existence of other competing heavy metal ions might affect the adsorptive elimination of one heavy metal ion. Therefore, to fully comprehend the adsorbent's efficiency and practical applications, the abatement of heavy metals in multicomponent systems is important. In the current study, the multicomponent adsorption of heavy metals from different complex mixtures, such as binary, ternary, quaternary, and quinary solutions, utilizing various adsorbents are reviewed in detail. According to the systematic review, the adsorbents made from locally and naturally occurring materials, such as biomass, feedstocks, and industrial and agricultural waste, are effective and promising in removing heavy metals from complex water systems. The systematic study further discovered that numerous studies evaluate the adsorption characteristics of an adsorbent in a multicomponent system using various important independent adsorption parameters. These independent adsorption parameters include reaction time, solution pH, agitation speed, adsorbent dosage, initial metal ion concentration, ionic strength as well as reaction temperature, which were found to significantly affect the multicomponent sorption of heavy metals. Furthermore, through the application of the multicomponent adsorption isotherms, the competitive heavy metals sorption mechanisms were identified and characterized by three primary kinds of interactive effects including synergism, antagonism, and non-interaction. Despite the enormous amount of research and extensive data on the capability of different adsorbents, several significant drawbacks hinder adsorbents from being used practically and economically to remove heavy metal ions from multicomponent systems. As a result, the current systematic review provides insights and perspectives for further studies through the thorough and reliable analysis of the relevant literature on heavy metals removal from multicomponent systems.

Competitive adsorption analysis of antibiotics removal from multi-component systems using chemically activated spent tea waste: effect of operational parameters, kinetics, and equilibrium study

In this study, spent tea powder waste was chemically treated for the synthesis of adsorbent using two activating agents, i.e., sulfuric acid and phosphoric acid, to obtain sulfuric acid activated carbon (SAC) and phosphoric acid activated carbon (PAC). The performance of PAC and SAC for the sorption of tetracycline (TCY) and sulfadiazine (SDZ) antibiotics from mono-component (SDZ/TCY) and multi-component (SDZ + TCY) adsorption systems was investigated. Synergistic and antagonistic effects were studied in removing target pollutants in SDZ + TCY systems. Kinetic and equilibrium studies were modeled by different kinetic and isotherm models. The adsorption capacity was assessed using Langmuir's competitive model in a [Formula: see text]. Pseudo-first-order kinetic and Langmuir isotherm models best fit the experimental kinetic and equilibrium data to remove antibiotics. The Langmuir's maximum adsorption capacity (q_m) of PAC for the removal of SDZ and TCY in a [Formula: see text] was found to be 16.75 and 10.87 mg/g, and q_m of SAC for the removal of SDZ and TCY was found to be 24.69 and 23.20 mg/g, respectively. In SDZ + TCY multi-component system, adsorption of TCY was synergistic in nature for both PAC and SAC. Sorption of SDZ displayed an antagonistic effect in the SDZ + TCY system for both SAC and PAC. In conclusion, the activated carbons synthesized from spent tea waste could be effectively adopted for the simultaneous adsorption of SDZ and TCY from multi-component systems.

Adsorption technique for the removal of heavy metals from wastewater using low-cost natural adsorbent

The primary goal of this study was to use low-cost adsorbents, this achieves by using pine cones as plant waste adsorbents in the treatment of industrial wastewater. In the experimental work of this study, a system of PVC horizontal pipes of 15cm diameter and 600 cm length without membranes was used. The polluted water values discharged in the system were 20, 40, 60, 80, and 100 L/hr. The effect of many hydraulic parameters (contact time, flow discharge, length of the pipe, and pressure) with environmental parameters (pH, TDS, TSS and electrical conductivity) was investigated in this continuous flow system. The sample of plant waste (pine cone) was treated and activated by ozonation, to manufacture new media with high porosity, activated carbon developed from pine cone (ACPC), and to determine the activity that produces the best results in the removal of heavy metals. To remove Fe+2 and Zn+2 ions from industrial wastewater, activated carbon was used as an adsorbent. Adsorption tests result in an exhibit that, the ACPC adsorbent had remarkable heavy metals removal efficiency. The most effective removal efficiency of 95% of Zn+2 was recorded at pH 7, 20 l/hr, and 5hrs. The higher removal efficiency of 96.67% of Fe+2 occurred at pH 6, 20 l/hr, and 5hr. The study also revealed that activated carbon devolved from pine cones can be adopted as a low-cost alternative for removing metal ions.

Adsorptive removal of pharmaceutically active compounds from multicomponent system using Azadirachta indica induced zinc oxide nanoparticles: analysis of competitive and cooperative adsorption

In this research, zinc oxide (ZnO) nanoparticles synthesized using neem leaf (Azadirachta indica) extract were used as an adsorbent for removing two widely used pharmaceutical compounds acetaminophen (AMP) and sulfadiazine (SDZ). The synthesized ZnO nanoparticles were characterized using SEM-EDS, FTIR, TEM, BET, and XRD analysis. The synthesized ZnO nanoparticles were found to be in the size range of 10 nm with a surface area of 48.551 m²/g. The adsorptive performance of ZnO nanoparticles in both mono-component (MoS) and multi-component system (MuS) was investigated under various operational parameters viz. contact time, temperature, pH, concentration of pharmaceutical compound and ZnO nanoparticles dose. It was observed that the maximum adsorption capacity of ZnO nanoparticles was 7.87 mg/g and 7.77 mg/g for AMP and SDZ, respectively, under the optimum conditions of 7 pH and 2 g/L adsorbent dosage. The experimental data best-fitted with the pseudo-second-order model and Langmuir model, indicating monolayer chemisorption. Further investigation on removal of AMP and SDZ from multicomponent system was modelled using a Langmuir competitive model. The desorption study has shown 25.28% and 22.4% removal of AMP and SDZ from the surface of ZnO nanoparticles. In general, green synthesized ZnO nanoparticles can be utilized effectively as adsorbent for removal of pharmaceutically active compounds from wastewater.

Testing Thymol-Based DES for the Elimination of 11 Textile Dyes from Water

Textile industries release dangerous wastewater that contain dyes into the environment. Due to their toxic, carcinogenic and mutagenic nature, they must be removed before the discharge. Liquid–liquid extraction has proven to be an efficient method for the removal of these dyes. As extractants, deep eutectic solvents (DESs) have shown excellent results in recent years, as well as presenting several green properties. Therefore, four different hydrophobic DESs based on natural components were prepared thymol:decanoic acid (T:D (1:1)), thymol:DL-menthol (T:M (1:1)), thymol:DL-menthol (T:M (1:2)) and thymol:coumarin (T:C (2:1)) for the extraction of Malachite Green (MG), Brilliant Blue G (BBG), Acid Yellow 73 (AY73), Reactive Red 29 (RR29), Acid Blue 113 (AB113), Reactive Black 5 (RB5), Remazol Brilliant Blue (RBB), Direct Yellow 27 (DY27), Acid Blue 80 (AB80), Direct Blue 15 (DB15) and Acid Violet 43 (AV43) dyes from water. The operational parameters of the liquid–liquid extraction were selected in order to save time and materials, resulting in 30 min of stirring, 15 min of centrifugation and an aqueous:organic ratio of 5:1. In these conditions, the highest values of extraction obtained were 99% for MG, 89% for BBG and 94% for AY73. Based on these results, the influence of the aqueous:organic phase ratio and the number of necessary stages to achieve water decolorization was studied.

Bioretention soil capacity for removing nutrients, metals, and polycyclic aromatic hydrocarbons; roles of co-contaminants, pH, salinity and dissolved organic carbon

Conventional bioretention soil media (BSM: e.g., loamy sand) is employed in infiltration-based stormwater management practices, but concerns exist on its limited sorption capacity. However, limited quantitative data is available, particularly considering the wide range of contaminants and water quality conditions that occur in stormwater. This study utilized batch tests to investigate the capability of conventional BSM for simultaneous removal of three nutrients (ammonium, nitrate, and phosphate), six metals (Cd, Cr, Cu, Ni, Pb and Zn), and four polycyclic aromatic hydrocarbons (PAHs: naphthalene, acenaphthylene, phenanthrene, and pyrene) from synthetic stormwater. Moreover, the effects of co-contaminants and different stormwater chemistry parameters (pH, salinity, and dissolved organic carbon (DOC)) on BSM sorption capacity were investigated. BSM was not effective for nutrients removal; however, it had good removal efficiency for metals such as Cu, Pb, and Cr which are less soluble at neutral pH values compared to metals such as Ni, Cd and Zn. Moreover, BSM was effective for removing PAHs with higher hydrophobicity such as pyrene and phenanthrene. Metals sorption capacity of BSM was greater at higher pH, lower salinity and DOC; however, the sorption capacity of BSM for PAHs was not sensitive to stormwater chemistry parameters. However, competitive sorption had a notable effect on low molecular weight PAHs, Cd, and Ni. This study provides a quantitative evaluation of the BSM performance and compares the sorption capacity to potential sorptive amendments used in stormwater management. While select sorbent amendments out-performed the BSM, this was not universal and was contaminant specific; careful consideration of water quality enhancement goals and solution chemistry are required in selecting a sorbent. Overall, this study identifies the possible limitations in BSM compositions and factors that may adversely affect BSM sorption capacity, and finally describes options to enhance BSM performance and recommendations for future research.

The effect of carbonization temperature on the capacity and mechanisms of Cd(II)-Pb(II) mix-ions adsorption by wood ear mushroom sticks derived biochar

Heavy metals often coexist in contaminated environmental media, and competition between heavy metals for adsorption sites influences the absorption capacity of biochar. In this study, the adsorption mechanism of pyrolytically modified wood ear mushroom sticks (250, 450, and 650 °C) as a new bio-adsorbent for single-ion and mixed-ion solutions Cd²⁺ and Pb²⁺ Biochar adsorption experiments showed that the adsorption abilities of Cd²⁺ and Pb²⁺ increased with increasing WMBC (wood ear mushroom sticks biochar) pyrolysis temperature. According to the Langmuir model, the maximum adsorption capacity of Cd²⁺ and Pb²⁺increased with higher pyrolysis temperature, being 29.84, 39.08, 46.16 mg·g^-1and 124.3, 186.8, 234.2 mg·g^-1, respectively for three different pyrolysis temperatures 250, 450, and 650 °C. WMBC exhibited a stronger adsorption ability for Pb²⁺ than for Cd²⁺. Competition between the two heavy metals severely inhibited the adsorption of Cd²⁺. Based on X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR) analyses, the dominant interaction mechanisms were determined to be complexation, ion exchange, precipitation, and C-π interaction. The results suggest WMBC shows promise as a novel, cheap, and effective adsorbent that can be used to remove both Cd²⁺ and Pb²⁺ pollutants from environmental media.

A Review of the Modeling of Adsorption of Organic and Inorganic Pollutants from Water Using Artificial Neural Networks

The application of artificial neural networks on adsorption modeling has significantly increased during the last decades. These artificial intelligence models have been utilized to correlate and predict kinetics, isotherms, and breakthrough curves of a wide spectrum of adsorbents and adsorbates in the context of water purification. Artificial neural networks allow to overcome some drawbacks of traditional adsorption models especially in terms of providing better predictions at different operating conditions. However, these surrogate models have been applied mainly in adsorption systems with only one pollutant thus indicating the importance of extending their application for the prediction and simulation of adsorption systems with several adsorbates (i.e., multicomponent adsorption). This review analyzes and describes the data modeling of adsorption of organic and inorganic pollutants from water with artificial neural networks. The main developments and contributions on this topic have been discussed considering the results of a detailed search and interpretation of more than 250 papers published on Web of Science ® database. Therefore, a general overview of the training methods, input and output data, and numerical performance of artificial neural networks and related models utilized for adsorption data simulation is provided in this document. Some remarks for the reliable application and implementation of artificial neural networks on the adsorption modeling are also discussed. Overall, the studies on adsorption modeling with artificial neural networks have focused mainly on the analysis of batch processes (87%) in comparison to dynamic systems (13%) like packed bed columns. Multicomponent adsorption has not been extensively analyzed with artificial neural network models where this literature review indicated that 87% of references published on this topic covered adsorption systems with only one adsorbate. Results reported in several studies indicated that this artificial intelligence tool has a significant potential to develop reliable models for multicomponent adsorption systems where antagonistic, synergistic, and noninteraction adsorption behaviors can occur simultaneously. The development of reliable artificial neural networks for the modeling of multicomponent adsorption in batch and dynamic systems is fundamental to improve the process engineering in water treatment and purification.

Synergic adsorption performance of activated carbon prepared from Chinese prickly ash seeds

Waste residue of Chinese prickly ash seeds were simply treated with aqueous ZnCl₂ to prepared the high-performed activated carbon. It was characterized by the methods of XRD, SEM, EDX, FT-IR, BET and XPS. The synergetic adsorption performance of Chinese prickly ash seeds activated carbon for Pb²⁺, Ni²⁺ and Acid Orange IΙ (AO) was studied. In the single-component system, the adsorption capacity of Pb²⁺, Ni²⁺ and AO were 15.1, 10.7 and 188.4 mg/g, respectively. In the AO-Pb²⁺ system, the maximum adsorption capacity of Pb²⁺ and AO were 79.40 and 332.68 mg/g under temperature of 30°C and pH of 5.0, respectively. For AO-Ni²⁺ system, it was 375.6 and 38.3 mg/g, respectively. The adsorption kinetics was satisfactorily fitted by the pseudo-second-order model. The synergic adsorption process can be smoothly described by the non-modified Sips isotherm.

Adsorption of lead, copper and zinc in a multi-metal aqueous solution by waste rubber tires for the design of single batch adsorber

Heavy metal pollution has emerged as one of the most serious environmental challenges facing the world today. The removal of heavy metals from the effluent is of special environmental concern because of their toxicity and persistence in nature. This study presents the suitability of activated carbon from waste rubber tire as a low-cost adsorbent for multiple adsorption of copper, lead and zinc from wastewater. The adsorbent removed heavy metal ions effectively from solution medium in the order of copper > lead > Zinc. The adsorption process was rapid with all metals reaching equilibrium within 120 min. The optimum pH for Lead was achieved at 5 and 6 for copper and Zinc. The removal of heavy metals was discovered to increase with adsorbent dosage and contact time and reduced with initial concentration. The adsorption of multiple heavy metals was modeled using Freundlich and Langmuir adsorption isotherms to assess the experimental findings. The equilibrium data better fitted to the Langmuir isotherm with regression coefficient (R2) of 0.9831, 0.9992 and 0.9953 for lead, copper and zinc respectively. The maximum adsorption capacities (Qmax) at equilibrium were 9.6805 mg/g, 12.4378 mg/g and 4.9950 mg/g for Lead, Copper and Zinc respectively. The adsorption kinetics indicated that pseudo-second-order kinetic model described well the sorption mechanism for multiple adsorption of heavy metals with R2 of more than 0.99 for all metal ions. An empirical model for predicting and designing of a single batch adsorber for 95 % multiple heavy metal ion removal at any given initial heavy metal ion concentration and effluent volume was further developed using activated carbon from waste rubber tires. Waste rubber tire Activated carbon demonstrated an ability for the treatment of wastewater containing these heavy metals in multimetal solutions.

Multicomponent adsorption of pentavalent As, Sb and P onto iron-coated cork granulates

The assessment of multicomponent adsorption of pentavalent metalloids is important since they are often found together in groundwaters and mining runoff. For this purpose, adsorption of As(V), Sb(V) and P(V) onto iron-coated cork granulates was studied in binary and ternary systems. Data from equilibrium and kinetic studies revealed that uptake of these contaminants is a multilayer, heterogeneous process well described by Freundlich, extended Freundlich and Elovich models. Most of the observed interactions are competitive and were related to the chemical structure and aqueous behaviour of each anion. Sb(V) adsorption was found to be most impaired and P(V) uptake the least affected by the presence of other pentavalent anions. The aggravation in the reduction of adsorbed amount from binary to ternary solution was more prominent for As(V) than Sb(V). Sb(V) adsorption outweighed that of the other pnictogens in acidic solutions, but in neutral conditions As(V) or P(V) adsorption may predominate instead. P(V) adsorption was the most sensitive to electrolyte addition, namely Ca salts, which may promote precipitation of calcium phosphates. This work provides useful insights regarding the design of adequate adsorption treatment systems for the simultaneous treatment of pentavalent metalloids.

Use of bone char prepared from an invasive species, pleco fish (Pterygoplichthys spp.), to remove fluoride and Cadmium(II) in water

In this study, bone char (BC) from pleco fish (Pterygoplichthys spp.) was synthesized, and their textural and physicochemical properties, as well as its adsorption capacity towards fluoride and Cd(II) from single and binary aqueous solutions, were determined. The results showed that the properties of the BCs were independent of the type of bone used and the surface areas were close to 110 m² g^-1. The effect of solution pH revealed that the adsorption capacity of BC towards fluoride from water raised by decreasing the solution pH. This trend was attributed to the electrostatic interaction between the positively charged surface and the fluoride in aqueous solution. On the contrary, the capacity of BC for adsorbing Cd(II) was enhanced by increasing the solution pH, indicating that electrostatic interactions were also essential but with a contrary effect in comparison with fluoride adsorption due to the negatively charged surface at pH above the point zero charge (pH_PZC = 8.16). The experimental data for binary adsorption of fluoride and Cd(II) were interpreted satisfactorily using the modified Freundlich multicomponent isotherm (EFMI), and the experimental data revealed that Cd(II) have an antagonistic effect on the adsorption of fluoride, whereas the presence of fluoride does not affect the capacity of BC for adsorbing Cd(II). Thermogravimetric, XRD diffraction and IR spectroscopy analysis corroborated that the adsorption of fluoride in BC is due to electrostatic attractions, ion exchange or chemisorption and physisorption. Besides, the removal of Cd(II) occurs by physical adsorption and ion exchange. It was concluded that BC is an alternative material for the removal of fluoride and Cd(II) from aqueous solutions, and it is a possible application for using the bones of this invasive fish species.

Simultaneous Adsorption of Cationic Dyes from Binary Solutions by Thiourea-Modified Poly(acrylonitrile-co-acrylic acid): Detailed Isotherm and Kinetic Studies

In this study, simultaneous adsorption of cationic dyes was investigated by using binary component solutions. Thiourea-modified poly(acrylonitrile-co-acrylic acid) (TMPAA) polymer was used as an adsorbent for uptake of cationic dyes (malachite green, MG and methylene blue, MB) from aqueous solution in a binary system. Adsorption tests revealed that TMPAA presented high adsorption of MG and MB at higher pH and higher dye concentrations. It suggested that there are strong electrostatic attractions between the surface functional groups of the adsorbent and cationic dyes. The equilibrium analyses explain that both extended Langmuir and extended models are suitable for the description of adsorption data in the binary system. An antagonistic effect was found, probably due to triangular (MG) and linear (MB) molecular structures that mutually hinder the adsorption of both dyes on TMPAA. Besides, the kinetic studies for sorption of MG and MB dyes onto adsorbent were better represented by a pseudo-second-order model, which demonstrates chemisorption between the polymeric TMPAA adsorbent and dye molecules. According to experimental findings, TMPAA is an attractive adsorbent for treatment of wastewater containing multiple cationic dyes.

Effect of anions species on copper removal from wastewater by using mechanically activated calcium carbonate

In this work, the wastewater containing sulfate ions, nitrate ions or chloride ions was used to investigate the performance of anions in copper removal by mechanically activated calcium carbonate. The copper removal from wastewater containing sulfate anion achieved almost 99% with the CaCO₃/Cu molar ratio of 1:1. However, the copper removal from wastewater containing nitrate and chloride anions are lower than 20% and 35%, respectively. The precipitations from wastewater containing different anions were analyzed by using XRD, FTIR, SEM-EDS and XPS, respectively. Cu (II) in wastewater containing sulfate anion is precipitated in the form of posnjakite. The nitrate anion precipitates as gerhardtite, whereas chloride anion as atacamite and botallackite. The solubility of precipitation plays a decisive role in copper removal so that sulfate anions have a superior effect on Cu (II) precipitation due to relatively stable posnjakite with the lowest solubility, suggesting that this method using mechanically activated calcium carbonate is more suitable and effective for the wastewater containing sulfate anion.

Facile and scalable synthesis of magnetite/carbon adsorbents by recycling discarded fruit peels and their potential usage in water treatment

In this study, apple, banana and orange peels were used as precursor compounds for the mass production of magnetite/carbon adsorbents. A so-called "soak-calcination" procedure was employed by firstly soaking these waste fruit peels in FeCl₃ aqueous solutions and secondly calcining these precursors in the nitrogen atmosphere to yield final magnetite/carbon composites. This approach is quite simple and effective to synthesize carbon-based adsorbents on an industrial scale. The as-produced adsorbents feature the merits of appropriate ferromagnetism (>4emug^-1), high adsorption capacity (several hundreds of milligrams per gram for adsorption of methyl blue, Congo red, rhodamine B and Cr⁶⁺ ions), and good regenerability (>85%).

The Adsorption of Pb, Zn, Cu, Ni, and Cd by Modified Ligand in a Single Component Aqueous Solution: Equilibrium, Kinetic, Thermodynamic, and Desorption Studies

In this investigation, an amino functionalized adsorbent was developed by grafting 4-aminobenzoic acid onto the backbone of cross-linked chitosan beads. The 3 sets of beads including chitosan (CX), glutaraldehyde cross-linked chitosan (CCX), and 4-aminobenzoic acid grafted cross-linked chitosan (FGCX) were characterized by FTIR, XRD, SEM, and TGA. The water content and amine concentration of FGCX were determined. The effect of adsorption parameters was studied and the optimum was used for further studies. Equilibrium data was obtained from the adsorption experiment carried out at different initial concentration; the data were applied in isotherm, thermodynamics, and kinetic studies. The Langmuir and Dubinin-Kaganer-Radushkevich (DKR) models were successful in describing the isotherm data for the considered metal ions while the Freundlich and Temkin model fit some of the considered metal ions. Pseudo-second-order and intraparticle model described the kinetic data quite well. Thermodynamic parameters such as Gibb's free energy change (ΔG^o ), enthalpy change (ΔH^o ), and entropy change (ΔS^o ) were calculated and the results showed that the adsorption of Pb, Cu, Ni, Zn, and Cd ions onto FGCX is spontaneous and endothermic in nature. Regeneration of the spent adsorbent was efficient for the considered metal ions.

Removal of copper, nickel and chromium mixtures from metal plating wastewater by adsorption with modified carbon foam

In this study, the characterizations and adsorption efficiencies for chromium, copper and nickel were evaluated using manufacture-grade Fe2O3-carbon foam. SEM, XRD, XRF and BET analyses were performed to determine the characteristics of the material. Various pore sizes (12-420 μm) and iron contents (3.62%) were found on the surface of the Fe2O3-carbon foam. Fe2O3-carbon foam was found to have excellent adsorption efficiency compared to carbon foam for mixed solutions of cationic and anionic heavy metals. The adsorption capacities for chromium, copper and nickel were 6.7, 3.8 and 6.4 mg/g, respectively, which were obtained using a dual exponential adsorption model. In experiments with varying dosages of the Fe2O3 powder, no notable differences were observed in the removal efficiency. In a fixed-bed column test, Fe2O3-carbon foam achieved adsorption capacities for chromium, copper and nickel of 33.0, 12.0 and 9.5 mg/g, respectively, after 104 h. Based on these results, Fe2O3-carbon foam was observed to be a promising material for treatment of plating wastewater.

Removal of toxic zinc from water/wastewater using eucalyptus seeds activated carbon: non-linear regression analysis

In the present study, a novel activated carbon was prepared from low-cost eucalyptus seeds, which was utilised for the effectively removal of toxic zinc from the water/wastewater. The prepared adsorbent was studied by Fourier transform infrared spectroscopy and scanning electron microscopic characterisation studies. Adsorption process was experimentally performed for optimising the influencing factors such as adsorbent dosage, solution pH, contact time, initial zinc concentration, and temperature for the maximum removal of zinc from aqueous solution. Adsorption isotherm of zinc removal was ensued Freundlich model, and the kinetic model ensued pseudo-second order model. Langmuir monolayer adsorption capacity of the adsorbent for zinc removal was evaluated as 80.37 mg/g. The results of the thermodynamic studies suggested that the adsorption process was exothermic, thermodynamically feasible and impulsive process. Finally, a batch adsorber was planned to remove zinc from known volume and known concentration of wastewater using best obeyed model such as Freundlich. The experimental details showed the newly prepared material can be effectively utilised as a cheap material for the adsorption of toxic metal ions from the contaminated water.