Adsorbent For Removal Of Cd Research Articles

Adsorptive Removal of Cd(II) Ions from Water by a Cheap Lignocellulosic Adsorbent and Its Reuse as a Catalyst for the Decontamination of Sulfamethoxazole.

The work reports the removal of cadmium from water by applying an efficient low-cost lignocellulosic adsorbent, rooibos tea waste. The cadmium-loaded rooibos tea waste was used for the photocatalytic abatement of sulfamethoxazole to cater to the setback of secondary pollution mostly associated with the adsorption technique. The rooibos tea waste adsorbent displayed a high removal efficiency of about 90.63% for 10 mg/L Cd(II) ions at 45 °C, 180 min agitation time, pH 7, and a dosage of 500 mg. The process of Cd(II) adsorption was endothermic and spontaneous. Also, the spent adsorbent was found to be efficient toward the photocatalytic breakdown of 10 mg/L sulfamethoxazole with a degradation efficiency of 69% after 150 min. In addition, the extent of mineralization of the sulfamethoxazole by the spent adsorbent as obtained from the total organic carbon data was found to be 53%. Therefore, based on the results obtained from this work, rooibos tea waste lends itself as a cheap, eco-friendly, easily sourced, and viable adsorbent for the removal of toxic ions like Cd(II). Also, the successful reuse of the spent adsorbent is a promising approach to cater to the major setback of secondary pollution associated with adsorption technology.

Adsorptive removal of cadmium from electroplating wastewater using hybrid composite of thiol-grafted seed gum of Tamarindus indica and Teff hay biocarbon

Abstract This study examined the methods for preparing biocarbon from Teff hay (TBC) and thiol-grafted seed gum of Tamarindus indica (TH@TI-TBC) with the purpose of removing cadmium (Cd) from polluted electroplating waste water. To improve biocarbon adsorption, seed gum and thiol were added in a two-step combination. At a pH of 5.5, the most effective Cd adsorption was seen with TH@TI-TBC (261.47 mg g−1). While comparing to the Freundlich and Temkin models, the Langmuir and pseudo-second-order kinetic models found to be the best fit to the obtained adsorption data. After being treated with electroplating wastewater having 30 mg−1 L of cadmium, TH@TI-TBC was able to remove up to 89 % of the Cd, proving its effectiveness in dealing with adsorptive removal of Cd. Experimental studies and computational analyses revealed that electrostatic interaction and surface complexation were the principal underlying processes for Cd removal by TH@TI-TBC. In addition, an innovative material that can transform the waste into a product for environmental remediation must be developed using the vast amounts of Teff hay that are generated as agro-residue. So, this work proved that TH@TI-TBC can be made from Teff hay biocarbon could be a potential candidate for removing Cd from industrial wastewater.

W2O7 decorated polyindole nanocomposites: A dual-function platform for efficient removal and electrochemical sensing of cadmium metal ion

Our research presents a simple approach for synthesizing W2O7 decorated polyindole nanocomposites for electrochemical detection and adsorptive removal of Cd(II) ions from water. In the adsorption experiments, various parameters including temperature (ranging from 303 to 333 K), initial pH levels (ranging from 2 to 10), interaction time, amount of adsorbent (from 0.32 to 3.2 g/L), and initial concentrations (from 20 to 110 mg/L) were examined to identify the optimum conditions. The results of these studies demonstrated that the removal efficiency of Cd(II) were obtained to be 93.02% at the optimum pH of 7. Detailed adsorption isotherm and kinetic studies reveal that Cd(II) removal follows the Langmuir isotherm and pseudo-second-order (P-so) kinetic model. The PI-W2O7 NCs exhibited an estimated maximum adsorption capacity of 41.32 mg/g for Cd(II). Adsorption-desorption cycle of the Cd(II) laden PI-W2O7 NCs was effectively performed using HCl as an eluent. To enable electrochemical sensing of Cd(II) ions by PI-W2O7 NCs, the cyclic voltammetry (CV) method was employed. Intriguingly, distinct electrochemical responses were observed in our experimental observations, which stemmed from the interaction between the target analyte and the surface of PI-W2O7. The optimized conditions for the detection of Cd(II) using PI-W2O7 NCs were determined to be a concentration of 150 ppb and a pH of 7. The sensitivity and limit of detection (LOD) for Cd(II) ions were determined to be 1.719 μA/ppb cm2 and 1.072 ppb, respectively. The exceptional properties exhibited by PI-W2O7 NCs position them as a promising solution for the simultaneous detection and elimination of Cd(II) ions from water sources.

The use of new class α-amino nitrile modified magnetic adsorbents for removal of Cd(II) from aqueous medium: Sorbent modification vs. α-amino nitrile addition to the adsorption medium

In the present work, some novel α-amino nitriles were prepared: amino-2- (anthracen-9-yl) acetonitrile (AAN), and 2-(naphthalen-1-yl) -2- ((triethoxysilyl) propyl) amino) acetonitrile (Si-AN). With the aid of other organic compounds (3-aminopropyl triethoxysilane “APTES” and tetraethyl orthosilicate “TEOS”), the following carbon nanotubes “CNT” and magnetite “Mag” based adsorbents were prepared: CNT-AAN, Mag-SiO2, Mag-SiO2-APTES, Mag-SiO2-Si-AN. The FT-IR, 1H and 13C NMR spectroscopy proved the formation of (C N) and (NH-) bonds which indicated successful amino nitrile modification of the adsorbents. The ability of the above-mentioned adsorbents to remove cadmium “Cd(II)” from water was studied at various pH values. CNT modification with AAN reduced Cd(II) uptake, while all Mag modifications increased Cd uptake. The addition of AAN to the extraction medium with CNT sorbent reduced Cd(II) uptake. The addition of TEOS and Si-AN to the extraction medium for Cd(II) removal using Mag was studied where a positive impact was observed. Based on the above experiments, it was decided to use Mag as adsorbent with the addition of Si-AN to the extraction medium. Method optimization recommended pH 8 and Cd:Si-AN molar ratio of 1:1. The maximum adsorption capacity towards Cd(II) achieved in this study was 65 mg g−1. The method selectivity, re-usability and applicability on well water and tap water samples gave appropriate results. The adsorption of Cd(II) on Mag in the presence of Si-AN was fast, endothermic, spontaneous, favored and physi-sorption was predominant.

Development and optimization of high–performance nano–biochar for efficient removal Cd in aqueous: Absorption performance and interaction mechanisms

Cadmium (Cd) pollution has aroused wide public attention due its high mobility, bioaccumulation and carcinogenic properties, and biochar has been proven as an efficient adsorbent for removal of Cd due to its environmentally friendly and economic approach. In this study, three variables (grinding time, rotational speed, and mass ratio of ball–to–powder) were established through response surface methodology and Box–Behnken design, and the preparation process of ball–milled biochar (BMBC) was successfully optimized. The results indicated that the impact factors on Cd removal by BMBC were in the order of milling speed > grinding time > ball to powder mass ratio, and the optimum parameters for Cd removal were found to be: milling time = 16 h, speed = 448 rpm, and ball to powder mass ratio = 1.5:100. BMBC (300 nm) has a dramatically larger specific surface area and pore volume by 22 and 15 times, respectively, and was companied with richer oxygen–containing functional groups. The adsorption of Cd2+ on BMBC conformed to the pseudo–second–order kinetic model and the Langmuir model. The maximum adsorption capacity of Cd2+ was 3 times that of BC. Precipitation and complexation were the main mechanisms for the adsorption of Cd. Therefore, BMBC was a promising and effective adsorbent for the removal of Cd, which has potential application value.

A novel slag composite for the adsorption of heavy metals: Preparation, characterization and mechanisms

The utilization of solid waste for resource recovery and production of value-added products is the theme of green chemistry. Currently, how to using solid wastes to prepare environmentally-functional materials with high performance and strength is one of the hot topics. In this research, electrolytic manganese residue (EMR) was thermally activated with calcite to prepare a silicon-based functionalized adsorbent (C-EMR) for the removal of cadmium (Cd2+, 467.14 mg/g) and lead (Pb2+, 972 mg/g). The thermodynamic results indicated that the removal process of Cd2+ and Pb2+ by C-EMR were endothermic and spontaneous. HNO3 can effectively strip the two adsorbed metals from C-EMR with the stripping efficiency of nearly 80% for Cd2+ and 99.92% for Pb2+, indicating that adsorption and ion exchange may be the main reason for the removal of the metals on C-EMR. Besides, surface precipitation was also responsible for removing some Pb2+ from the aquatic environment according to the X-ray photoelectron spectrometry (XPS) analysis. Results indicate that -SiO3- has stronger affinity with Pb2+ and Cd2+ than other groups ((-MnO2), –OH) by theoretical calculation (VASP, GGA-PBE). This study shows that this novel adsorbent (C-EMR) can be adopted as an environmentally-friendly, inexpensive and efficient adsorbent for removal of Cd2+ and Pb2+ from aquatic solution. This technique not only provides potential adsorbent for the elimination of heavy metals but also proposes an alternative route for the treatment and utilization of waste solid.

Removal of heavy metals using activated carbon from microwave steam activation of palm kernel shell

• Highly carbonized and stabilized porous palm kernel shell activated carbon was produced. • Microwave steam shortened activation time. • Cd 2+ and Pb 2+ adsorption data fitted well with Freundlich isotherm model. • Kinetic adsorption studies indicated that the pseudo-second-order well described the adsorption on Cd 2+ and Pb 2+ . The presence of toxic heavy metals contributes towards the deterioration in the quality of water resources. In this work, microwave steam activation (MSA) was conducted to convert palm kernel shell into activated carbon (PKSAC). MSA provided a rapid heating rate (up to 140 °C/min) at 700 °C under a steam flow rate of 5 g/min for 45 min. PKSAC was obtained, showing high BET surface area (539.75 m 2 /g) with low H/C and O/C ratios, indicating a high degree of carbonization and stability of PKSAC to act as a durable adsorbent. The PKSAC was then applied to remove heavy metals (i.e. Cd 2+ and Pb 2+ ) present in landfill leachate (LL). Batch experiments were performed to investigate the effects of initial ion concentrations and contact times on Cd 2+ and Pb 2+ adsorption under optimal condition. Maximum Cd 2+ and Pb 2+ removal of 116.0 mg/g and 59.9 mg/g, respectively were obtained at pH 3, initial concentration of 100 mg/L, and adsorbent dose of 0.2 g. Results showed that the adsorption kinetics of Cd 2+ and Pb 2+ can be described by the pseudo second order kinetics model, while Freundlich isotherm was well fitted to the Cd 2+ and Pb 2+ adsorption data. Overall, the PKSAC produced by MSA is a promising and cost-effective adsorbent for removal of Cd 2+ and Pb 2+ .

Selective removal of Cd(II), As(III), Pb(II) and Cr(III) ions from water resources using novel 2-anthracene ammonium-based magnetic ionic liquids

Facile synthesis of two 2-anthracene ammonium-based magnetic ionic liquids (MILs), 2-anthracene ammonium tetrachloroferrate (III) ([2A-A]FeCl 4 ) and 2-anthracene ammonium trichlorocobaltate (II) ([2A-A]CoCl 3 ) was performed by protonation of 2-aminoanthracene, followed complexation with FeCl 3 /CoCl 2 . The MILs were tested in the adsorptive removal of Cd 2+ , As 3+ , Pb 2+ and Cr 3+ from water sources. Upon treatment with 10 mg dosage of MILs in 10 mL aqueous solution of 50 ppm each of Cd 2+ , As 3+ , Pb 2+ and Cr 3+ , adsorption capacity (mg/g) in the range of 5.73–55.5 and 23.6–56.8 for [2A-A]FeCl 4 and [2A-A]CoCl 3 respectively were recorded. Thus, the optimization, kinetic and isotherms studies were conducted using the [2A-A]CoCl 3 adsorbent. The [2A-A]CoCl 3 was more effective in pH 7–9, and equilibrium adsorption was achieved after 60 min contact time. The adsorption process proceeded via the Pseudo-second order pathway and the Langmuir isotherm model is the best fit for the adsorption process (with q max = 227 – 357 mg/g) of all the targeted metal ions. The [2A-A]CoCl 3 adsorbent demonstrated practicality with large distribution and selectivity coefficients of the targeted ions, and up to six times regeneration.

Prosopis Juliflora (Kikar) pods as adsorbent for removal of Cd(II) ions from aqueous streams

Cadmium Cd(II) is a heavy metal, the presence of which in an aqueous ecosystem is detrimental to human beings, animals and vegetation due to its mobile, toxic and non-biodegradable nature. Different treatment techniques like neutralization, coagulation and flocculation, oxidation, ion exchange, ozonation, membrane separation and disinfection have been employed, but eco-friendly techniques involving adsorption on natural and bio-degradable adsorbents is the most favourable one as it is the least costly, flexible in design and possesses large removal efficiencies. The present work is based on the adsorptive removal of Cd(II) ions from wastewater streams employing biosorbent prepared from Prosopis Juliflora (kikar) pods. To determine the parametric sensitivity of the adsorptive removal, batch experiments have been carried out by varying the dosage of the adsorbent, initial Cd(II) concentration, pH and the time of contact. The chemical/microstructural composition of adsorbent prepared from raw and carbonized kikar pods has been examined by its proximate analysis, SEM and FTIR. The carbonized kikar pods can act as an economical, eco-friendly and practical adsorbent for Cd(II) from wastewater streams as they displayed a maximum removal efficiency of 82% and a maximum metal uptake capacity of 16 mg g−1 of biosorbent. Further, to comprehend the kinetic data for the adsorptive removal, a pseudo-second order mechanism has been proposed.

Thiol–ended polycaprolactone: Synthesis, preparation and use in Pb(II) and Cd(II) removal from water samples

In the present study, thiol–ended polycaprolactone (TPCL) was successfully prepared by “ring opening polymerization” using 2-3 dimercaptopropanol and caprolactone. The synthesized material was employed as a possible adsorbent for removal of Cd(II) and Pb(II) ions from water samples and the influence of essential parameters (pH of 5.0, adsorbent dosage of 10.0 mg and contact time of 30.0 min) on the adsorption process was studied. Different techniques (BET NMR, FTIR, zeta potential, TGA/DTG) were used to characterize physical and chemical properties of the polymer. Various isotherm and kinetic models were employed to understand plausible mechanisms involved in the adsorption. It is revealed that adsorption process fitted very well with the Langmuir isotherm and pseudo-second-order kinetic models for both of the ions. The adsorption capacity decreased slightly (< 10%), demonstrating the thiol–ended polycaprolactone performance even after four consecutive adsorption–desorption cycles. The spike recovery studies with real water samples yielded recoveries of over 90% which indicated the applicability of the method. As a result, thiol–ended polycaprolactone has been demonstrated to be effective sorbent for the removal of Cd(II) and Pb(II) ions from aqueous solution, indicating its potential relevance in water remediation.

Thermally processed biochar: preparation, characterisation and their application for cadmium removal from surface and groundwater

ABSTRACT The thermally modified Parthenium biochar was used as an efficient adsorbent for removal of Cd from water. Parthenium biochar (PBC) prepared at 500°C was thermally activated by re-heating it at 700°C. PBC and thermally modified biochar (TMPBC) was characterised by FTIR, SEM-EDS, BET-surface area and XRD. The surface area of TMPBC (3.44 m2g−1) was higher than PBC (1.89 m2g−1). The optimum conditions for Cd adsorption was found to be pH, 5.0; biochar dose, 2.5 (g L−1); time, 30 min; temperature 25°C; initial Cd concentration, 100 mg L−1. Cadmium removal parameters were assessed using kinetic (pseudo first and second order) and adsorption models (Langmuir, Freundlich, and Redlich-Peterson). Cd removal followed pseudo second order kinetic model. The Cd removal capacity of TMPBC (129.2 mg g−1) was significantly higher than PBC (59.3 mg g−1). Cd removal by TMPBC (97–99%) was also demonstrated for a surface and underground waters. FTIR, XRD and SEM-EDS analysis confirmed the ion exchange and otavite precipitation mechanisms of Cd removal by biochar. The thermal modification technique could be an alternative for commercially available activated carbons; however this needs to be explored with different biomasses and other elements.

4-Aminoacetophenone Intercalated CoAl Layered Double Hydroxides: Synthesis, Characterization and Adsorptive Removal of Cd(II) ions from Water Samples

In the present study, CoAl-NO3 Layered Double Hydroxides (CoAl-NO3-LDH) was synthesized and an enolate anion of 4-Aminoacetophenone (AAP) was intercalated into LDH following the reconstruction approach. The CoAl-NO3-LDH and CoAl-AAP-LDH were characterized by Fourier-Transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analyses. CoAl-AAP-LDH worked well for adsorption of Cd(II) ions from aqueous samples at optimum pH 7, adsorbent dosage 25 mg, concentration of Cd(II) ions 25 mg L-1 and shaking time 20 min at 25 °C. Different isotherms such as Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms fitted well to adsorption data with correlation coefficient (R2) of 0.998, 0.982 and 0.992, respectively. Monolayered (Qm) and multi-layered (KF) capacities of CoAl-AAP-LDH for adsorption of Cd(II) ions were calculated and found to be 34.40 and 19.44 mg g-1, respectively. Sorption energy was calculated and found to be 9.13 kJ mol-1, indicating chemisorption or ion exchange sorption mechanism. The method worked well for the adsorption of Cd(II) ions from wastewater samples.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water.

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.

Adsorptive removal of Cd (II) using oil palm empty fruit bunch-based charcoal/chitosan-EDTA film composite

Oil palm empty fruit bunch (OPEFB) is a solid waste abundantly produced by the palm oil industry. This study aimed to prepare a film adsorbent from OPEFB-based charcoal (OC), embedded into chitosan-ethylenediaminetetraacetic acid (EDTA) matrix (OC/Chi-EDTA) through a simple phase inversion technique for Cd (II) removal. Based on the tensile strength (20.4 kgf/mm2) and adsorption capacity (66.6 mg/g), the material with 0.85 : 0.1: 0.15 was selected as the best film adsorbent using simple additive weighting. Further, the sample was characterized for its functional group, morphology, crystallinity, and thermal behavior. The characterizations revealed the successful preparation of OC/Chi-EDTA with advantageous properties for Cd (II) adsorptive removal such as rough surface morphology and amorphous structure (crystallinity = 41.02). Good thermal stability of OC/Chi-EDTA was also suggested by the Tpeak of the first composite degradation at 298.97°C. At equilibrium, the adsorption isotherm best fitted with the Langmuir isotherm model (R2 = 0.992; root-mean-square error = 2.75), where the maximum adsorption capacity was 283.33 mg/g. Investigation on the adsorption mechanisms found that electrostatic attraction and complexation were responsible for the Cd (II) uptake. At the optimum conditions (contact time = 120 min; pH 7), the adsorption capacity was recorded to be 67.2 mg/g with a removal efficiency of 99.56%. Regeneration studies suggested that OC/Chi-EDTA can be used up to four cycles (removal efficiency > 75%). In conclusion, the OC has been successfully embedded into chitosan-EDTA matrix resulting in a film adsorbent that could perform a high Cd (II) uptake.

Carboxymethyl Glucomannan from Amorphophallus oncophyllus as an Alternative Heavy Metal Removal from Wastewater: Adsorption of Cadmium and Zinc

Carboxymethyl glucomannan (CMGM) was successfully synthesized through the reaction of glucomannan from Amorphophallus oncophyllus and monochloroacetic acid, using NaOH as a catalyst. Two types of glucomannan were used in this study, low viscosity glucomannan (LGM) and high viscosity glucomannan (HGM). The produced CMGM were differentiated into LCMGM (synthesized from LGM) and HCMGM (synthesized from HGM). The CMGM structure was characterized by FTIR, and the degree of substitution (DS) was determined using back titration method. The DS value were 0.484 and 0.412 for LCMGM and HCMGM, respectively. Both CMGMs were then evaluated for its adsorption capacity towards Zn and Cd at the optimum pH of 6, with 60 minutes adsorption time for each sample. The maximum adsorption capacity of Zn was 13.61 mg/g and 13.04 mg/g for LCMGM and HCMGM, respectively. While for Cd, the maximum adsorption capacity of LCMGM and HCMGM was 17.70 mg/g and 15.90 mg/g. The adsorption capacity of the sample follows the Langmuir isotherm adsorption. In conclusion, CMGM from A. oncophyllus has demonstrated its potential as a reusable adsorbent for efficient removal of Cd and Zn.

A Mineral By-Product from Gasification of Poultry Feathers for Removing Cd from Highly Contaminated Synthetic Wastewater

Ash from poultry feather gasification was investigated as an adsorbent for Cd removal from synthetic wastewater under a range of operational conditions: initial pH (2–8) and salinity (8–38 mS/cm) of wastewater, ash dosage (2.5–50 g/L), Cd concentration (25–800 mg/L) and contact time (5–720 min). The ash was highly alkaline and had low surface area and micropores averaging 1.12 nm in diameter. Chemical/mineralogical analysis revealed a high content of P2O5 (39.9 wt %) and CaO (35.5 wt %), and the presence of calcium phosphate, hydroxyapatite and calcium. It contained only trace amounts of heavy metals, BTEX, PAHs and PCBs, making it a safe mineral by-product. Cd adsorption was described best with Langmuir and pseudo-second order models. At pH 5, an ash dosage of 5 g/L, 40 min contact time and 100 mg Cd/L, 99% of Cd was removed from wastewater. The salinity did not affect Cd sorption. The maximum adsorption capacity of Cd was very high (126.6 mg/g). Surface precipitation was the main mechanism of Cd removal, possibly accompanied by ion exchange between Cd and Ca, coprecipitation of Cd with Ca-mineral components and Cd complexation with phosphate surface sites. Poultry ash effectively removes high concentrations of toxic Cd from wastewater.

The biochars prepared from cinnamon and cannabis as nature-friendly adsorbents for removal of Cd(II) ions from aqueous solutions

Cinnamon and cannabis were utilized to produce biochars, which operate as promising adsorbents by pyrolysis in various temperatures using the N2 atmosphere. The novel biochars were analyzed via scanning electron microscopy, X-ray powder diffraction, Fourier-transform infrared spectroscopy, the pH point of zero charges, and N2 adsorption–desorption isotherm styles, followed by testing the adsorption attributes of these materials using Cd(II) ions in a water bath. The Cd(II) adsorption onto biochars was satisfied in the neutral pH of 7.0 and a temperature of 65 °C. The equilibrium data in aqueous solutions were fitted to Langmuir (L), Freundlich (F), Tempkin (T), and Redlich–Peterson (R–P) models. Kinetic adsorption data were analyzed using the pseudo-first-order (PFO), pseudo-second order (PSO), Elovich (E), and intraparticle diffusion (ID) models. In addition, the Cd(II) adsorption performance was proficiently narrated through Langmuir and pseudo-second-order models and electrostatic force and chemical reaction were originally responsible for adsorption mechanism. Further, the results demonstrated that the obtained qmax from biochars at the pyrolysis temperature of 600 °C was higher than that noticed at pyrolysis temperatures of 300 and 400 °C. Finally, the adsorbent dose of 0.1 g and temperature of 65 °C, as well as supplying qmax of 147.05, 153.84, 158.73, 133.33, 144.92, and 175.43 mg g−1 were observed for cinnamon 300, cinnamon 400, cinnamon 600, cannabis 300, cannabis 400, and cannabis 600, respectively.

Effective removal of Cd(II) from aqueous solution based on multifunctional nanoporous silicon derived from solar kerf loss waste

Recycling of kerf-loss slurry waste has become a meaningful and urgent issue in recent years. In this study, a novel hybrid material was prepared by Ag-assisted chemical etching kerf loss silicon waste and subsequently functionalized by a facile three-step graft process of 3-aminopropyltrimethoxy-silane, maleic anhydride, and ethylenediamine, named as EDA-MAH-APTES-NPSi, which could work as an effective adsorbent for removal of Cd(Ⅱ) from aqueous solution. The effect of initial pH, absorption duration, and metal ion concentrations on absorption performance were investigated. The adsorption equilibrium achieved after 120 min, the maximum adsorption capacity reached up to 210.01 mg/g and pH was at 5.5. The adsorption kinetic was fitted in the pseudo-second-order model and the Freundlich equation provided an accurate description for adsorption behavior. The XPS and FT-IR analysis manifested that Cd(Ⅱ) removal might be ascribed to the adsorption on the surface organic functional group by chemical chelating reaction and the ion exchange reaction. The EDA-MAH-APTES-NPSi maintained excellent adsorption capacity which decreased approximately 15.3 % (from 40.5–34.3 mg/g) after five successive regenerated cycles. The work confirms the potential of Cd(Ⅱ) removal from aqueous solution based on the modified NPSi and opens up a new way for recycling silicon cutting waste.

Enhancing the removal performance of Cd(Ⅱ) from aqueous solutions by NaA zeolite through doped thiourea reduced GO which is trapped within zeolite crystals

In this study, thiourea reduced graphene oxide/NaA zeolite composite (tGO-Zeo) was successfully prepared by a facile two-step synthetic route and used as an efficient adsorbent for removal of Cd(II) from aqueous solution. Characterization of the composite material showed that tGO was entrapped within zeolite crystalline particles and intimately interacted with the zeolite framework. Furthermore, the presence of tGO considerably reduced zeolite crystal size and altered crystal morphology, turning cubic zeolite crystals of micrometer size into nanometer irregular particles. Batch adsorption experiment for Cd(II) removal was conducted and the adsorption performance of tGO-Zeo and Zeo (zeolite) were determined. It was shown that doped tGO significantly enhanced the adsorption capacity of zeolite by 31.54%. The adsorption mechanism differs for tGO-Zeo and Zeo, and tGO-Zeo has higher affinity for Cd(II). The adsorption capacity of tGO-Zeo with a tGO doping amount of 1.26% (wt%) was estimated to be 196 mg/g (1.74 mM/g) at 30 °C and superior to most previously reported zeolite based composites, which often contain large amounts of dopants. The effects of pH and ionic strength on adsorption suggest that ion exchange and coordination are responsible for Cd(II) adsorption by tGO-Zeo. Humic acid can slightly increase Cd(II) adsorption performance of tGO-Zeo, which may be due to tGO-Zeo—humic acid—Cd(II) complexes formation. Therefore, tGO-Zeo composite is a cost-effective and eco-friendly adsorbent for efficient removal of Cd(II) ions from aqueous solutions.

Preparation and characterization of a novel graphene/biochar composite and its application as an adsorbent for Cd removal from aqueous solution

A novel graphene/biochar composite (BG composite) was synthesized by mixing graphene (Gr) onto feedstock biomass followed by slow pyrolysis. The composite was then tested for its sorption capacity of Cd from aqueous solutions. Structure and morphology analysis showed that graphene was coated on the biochar surface, resulting in a larger surface area, more functional groups, greater thermal stability, and higher removal efficiency of Cd in comparison to unmodified biochar. The sorption capacity of the BG composite for Cd was 1.26-2.36 times that of biochar. A pseudo second-order model adequately simulated sorption kinetics. The sorption isotherms were simulated well by Langmuir models, and calculated maximum Cd adsorption capacities did not change significantly with increasing temperature. Thermodynamic parameters showed that the sorption process of Cd onto the BG composite was feasible and spontaneous. The results of the adsorption experiments, as well as the characteristics of biochar, demonstrate that the process of Cd adsorption on BG composites is mainly physical adsorption accompanied by other chemical adsorption phenomena, such as complexation and ion exchange. This study highlights the use of a BG composite as a multifunctional adsorbent for the efficient, economic, and environmentally friendly treatment of pollutants.