Adsorption of Phosphate by Amino-Functionalized and Co-condensed SBA-15

In this study, the applications of mesoporous materials based on silica, and those with modifications, namely post-synthetic grafting, co-condensation, and pure SBA-15, were investigated for the removal of phosphate from sewage. The mesostructures were confirmed by X-ray diffraction, Brunauer?CEmmett?CTeller, Fourier transform infrared spectroscopy, and transmission electron microscopy. The absorption of phosphate by the mesoporous adsorbents was examined, using different adsorption models to describe the equilibrium and kinetic data. The maximum adsorption capacities of the mesostructured adsorbents were found to be 69.970, 59.890, and 2.018?mg/g for the co-condensation, post-synthetic grafting, and pure SBA-15, respectively. The kinetic data showed that the adsorption of phosphate onto three different mesostructures followed the pseudo-first-order kinetic model.     

Comparison of Surface-Modified Adsorbents for Phosphate Removal in Water

Three novel composite adsorbents, sulfate-coated zeolite (SCZ), hydrotalcite (SCH), and activated alumina (SCAA), were characterized and employed for the removal of phosphate from aqueous solution using equilibrium and kinetic batch experiments. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrum were used to study the surface characteristics of the coated layer. Equilibrium tests showed that the adsorption of phosphate followed both Langmuir and Freundlich isotherms. The powder-type SCZ was better for phosphate removal (maximum binding energy, ???=?111.49?mg?g^?1) compared to hydrotalcite and activated alumina. The adsorption of phosphate was considered to take place mainly by ion exchange. The kinetic data followed a pseudo-second-order kinetic model. The initial adsorption of phosphate onto the sulfate-coated adsorbents was fast, indicating that the sulfate-coated materials developed in this study can be used as promising adsorbents for the removal of phosphate from wastewater or sewage.     

Combining Sewage Sludge and Clam Shell Waste to Prepare Adsorbents for Efficient Phosphorous Removal

Effluents containing phosphorous as phosphate ions are frequently discharged in freshwater resources contributing to the eutrophication and directly interfering in the biological equilibrium. Clam shell residues and sewage sludge were combined for preparing efficient adsorbents for phosphate removal from aqueous medium. The adsorbents were characterized before and after adsorption testing, and the adsorption equilibrium and kinetics were investigated. Phosphate removal of 89?±?1% was attained for samples prepared with 0.1?< X <?1.0, where X corresponds to sewage sludge/clam shell mass ratio. The analyses of the experimental errors indicated that the phosphorous removal followed the Elovich kinetic model, which describes adsorption in very heterogeneous surfaces. On the other hand, the best modelling was achieved using the Koble–Corrigan isotherm model, which incorporate different aspects of both Langmuir and Freundlich isotherms to represent the equilibrium data. The observed adsorption capacity (21.4 mgP g^?1) are comparable or greater to that observed for other adsorbents described in the literature.     

Adsorption of Cu2+ on Amine-Functionalized Mesoporous Silica Brackets

A directly amine-functionalized mesoporous silica (AMS) was prepared via an anionic surfactant-mediated synthesis method and used as adsorbents for deep removal of Cu²⁺ ions from aqueous solution at room temperature. The synthesized AMS had been characterized by X-ray diffraction, nitrogen physisorption measurement, and thermogravimetric analysis. The amine groups prefer to position to the surface of AMS material due to the S^?N⁺????I^? mechanism. Copper adsorption process had been studied from both kinetic and equilibrium points of view for AMS material. Experiments proved that the aqueous Cu²⁺ adsorption rates were fast and adsorption capacity was about 53.3?mg/g.     

Removal of Phenolic Compounds from Aqueous Solutions Using Sludge-Based Activated Carbons Prepared by Conventional Heating and Microwave-Assisted Pyrolysis

Sludge-derived activated carbons (ACs) were prepared by conventional heating and microwave pyrolysis. The ACs were characterized using several analytical and functional techniques and used for removal of six phenolic compounds from aqueous solutions. The adsorbents exhibited similar features and possessed hydrophobic surfaces. The ACs were assigned mesoporous materials, with specific surface areas of up to 641 and 540 m² g^?1 for CAC-500 and MAC-980, respectively. The preliminary results indicated that phenol removal onto the ACs increased in the order: m-cresol?<?phenol?<?o-cresol?<?2-chrorophenol?<?2-nitrophenol?<?hydroquinone. Hydroquinone exhibited the highest adsorption capacity and was chosen to continue the remaining part of the experimental work—kinetic and isothermal studies. The adsorption kinetic and isotherm data were well described by the Avrami fractionary order and Redlich–Peterson models, respectively. The maximum amounts (Q _max) of hydroquinone adsorbed at 25 °C were too high, reaching 1218.3 and 1202.1 mg g^?1 for CAC-500 and MAC-980, respectively. The mechanism of adsorption was proposed in this work, and it was suggested that donor–acceptor complex and π–π interactions play major roles in the adsorption process. The adsorbents were also tested on simulated effluents. The two ACs displayed good efficiency for the treatment of industrial simulated effluents.     

Tyrosinase-Immobilized MCM-41 for the Detection of Phenol

In the present investigation, we report the immobilization of the enzyme tyrosinase on mesoporous silica material, i.e. MCM-41 to serve as a tool for the detection of phenol. The enzyme immobilized onto the MCM-41 matrix has shown to retain its activity and is quite stable. The immobilization of enzyme has been discussed, and the various factors that affect the loading of enzyme onto MCM-41 were studied and optimized. The applicability of tyrosinase-immobilized MCM-41 was then demonstrated for the detection of phenol. The lowest detectable concentration of phenol by tyrosinase-immobilized MCM-41 was observed to be 1 mg l⁻¹. The factors influencing the detection of phenol were then studied in detail.     

Study of Phosphorus Removal by Using Sponge Iron Adsorption

Phosphorus is one of the key elements causing lake eutrophication. This paper deals with phosphate removal by Sponge iron in batch and fixed-bed operation. Isotherm and kinetic studies are conducted. The isotherm data is described by the Freundlich and Langmuir model, while the kinetic data of adsorption is fitted by the pseudo-second-order kinetic model. The saturated adsorption capacity of Langmuir isothermal equation is about 3.25 mg/g. The concomitant anions have adverse effect on phosphate adsorption and the effects follow the order: NO₃^??>?Cl^??>?SO₄^2?. The phosphate adsorption capacities of SI were improved significantly under the acidic condition. The results of the fixed-bed operation show that, with the increase of the influent phosphate concentrations, the breakthrough curve becomes steeper while the break point time decrease. According to the Adams–Bohart model, the critical height of the column decrease from 0.135 to 0.105 m when the contact time increased from 10 to 30 min with the influent concentration of 1.0 mg/L. According to BDST model, the critical bed depth is 0.15 m when the influent concentration of phosphate is 1.0 mg/L and the contact time (h) is 20 min.     

Co(II) Adsorption in Aqueous Media by a Synthetic Fe–Mn Binary Oxide Adsorbent

Co(II) adsorption on high-purity amorphous Fe?CMn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe?CMn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8?m²?g^?1 with a maximum capacity of 32.25?mg?g^?1. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07?kJ?mol^?1 indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe?CMn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.     

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

In this study, an iron?Czirconium binary oxide with a molar ratio of 4:1 was synthesized by a simple coprecipitation process for removal of phosphate from water. The effects of contact time, initial concentration of phosphate solution, temperature, pH of solution, and ionic strength on the efficiency of phosphate removal were investigated. The adsorption data fitted well to the Langmuir model with the maximum P adsorption capacity estimated of 24.9?mg P/g at pH?8.5 and 33.4?mg P/g at pH?5.5. The phosphate adsorption was pH dependent, decreasing with an increase in pH value. The presence of Cl^?, SO ₄ ^2? , and CO ₃ ^2? had little adverse effect on phosphate removal. A desorbability of approximately 53?% was observed with 0.5?M NaOH, indicating a relatively strong bonding between the adsorbed PO ₄ ^3? and the sorptive sites on the surface of the adsorbent. The phosphate uptake was mainly achieved through the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. Due to its relatively high adsorption capacity, high selectivity and low cost, this Fe?CZr binary oxide is a very promising candidate for the removal of phosphate ions from wastewater.     

Polydopamine Nanoparticles as a New and Highly Selective Biosorbent for the Removal of Copper (II) Ions from Aqueous Solutions

The adsorption and desorption of copper (II) ions from aqueous solutions were investigated using polydopamine (PD) nanoparticles. The nanoscale PD nanoparticles with mean diameter of 75?nm as adsorbent were synthesized from alkaline solution of dopamine and confirmed using scanning electron microscopy and X-ray diffraction analysis. The effects of pH (2?C6), adsorbent dosage (0.2?C0.8?g?L^?1), temperature (298?C323?K), initial concentration (20?C100?mg?L^?1), foreign ions (Zn²⁺, Ni²⁺, Cd²⁺, Fe²⁺, and Ag⁺), and contact time (0?C360?min) on adsorption of copper ions were investigated through batch experiments. The isotherm adsorption data were well described by the Langmuir isotherm model. The maximum uptake capacity of Cu²⁺ ions onto PD nanoparticles was found to 34.4?mg/g. The kinetic data were fitted well to pseudo-second-order model. Moreover, the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy) were studied.     

Methylene Blue Adsorption onto Water Hyacinth: Batch and Column Study

The adsorption of methylene blue cationic dye by water hyacinth root was studied in a batch system. The experimental data isotherms were analyzed using the Langmuir and Freundlich equations. The monolayer adsorption capacity for methylene blue dye was found as 0.187?kg?kg^?1. Three kinetic models (the pseudo-first order, the pseudo-second order, and the unified approach) were used to calculate the adsorption rate constants. The kinetic data along with equilibrium constants (maximum monolayer capacity and Langmuir constant) fitted well with unified approach model for different initial concentrations, and the rate constants were determined. Laboratory column experiments were conducted to evaluate the performance of water hyacinth root for methylene blue sorption under dynamic flow conditions. Breakthrough curves were plotted for the methylene blue adsorption on the adsorbent using continuous flow column operation by varying the bed height (0.06?C0.12?m) and the feed concentrations (0.1?C0.2?kg?m^?3). Different column design parameters, such as depth of exchange zone, adsorption rate, and adsorption capacity, were calculated. At the end, an attempt has also been made to model the data generated from column studies using the empirical relationship based on Bohart?CAdams model.     

Synthetic Iron Oxides for Adsorptive Removal of Arsenic

Removal of arsenic from water reservoirs is the issue of great concern in many places around the globe. As adsorption is one of the most efficient techniques for treatment of As-containing media, thus the present study concerns application of iron oxides-hydroxides (akaganeite) as adsorbents for removal of this harmful metal from aqueous solution. Two types of akaganeite were tested: synthetic one (A) and the same modified using hexadecyltrimethylammonium bromide (A_M). Removal of As was tested in batch studies in function of pH, adsorbent dosage, contact time, and initial arsenic concentration. The adsorption isotherms obey Langmuir mathematical model. Adsorption kinetics complies with pseudo-second-order kinetic model, and the constant rates were defined as 2.07?×?10^?3and 0.92?×?10^?3 g mg^?1 min^?1 for the samples (A) and (A_M), respectively. The difference was caused by significant decrease in adsorption rate in initial state of the process carried out for the sample A_M. The maximum adsorption capacity achieved for (A) and (A_M) akaganeite taken from Langmuir isotherm was 148.7 and 170.9 mg g^?1, respectively. The results suggest that iron oxides-hydroxides can be used for As removal from aqueous solutions.     

Equilibrium and Kinetic Characteristic of Adsorption of Cu2+, Pb2+ on a Novel Anionic Starch Microspheres

Neutral starch microspheres (NSMs) were synthesized with epichlorohydrin as the cross-linking agent from soluble starch by inverse microemulsion method. Anionic starch microspheres (ASMs) were prepared from NSMs by the secondary polymerization with chloroacetic acid as the anionic etherifying agent. Scanning electron microscopy (SEM) revealed that microspheres had good sphericity and fine dispersibility, and the average particle size was about 75 ??m. The adsorption procedure of Cu²⁺, Pb²⁺ on ASMs was carried out by batch experiments, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms, the adsorption equilibrium data were found to fit the Langmuir and Freundlich isotherm model, the Freundlich isotherm was more adequate than the Langmuir isotherm in simulating the adsorption isotherm of Cu²⁺,the adsorption of Cu²⁺, Pb²⁺ on ASMs was a spontaneous, the isosteric heat of adsorption at different adsorption levels was always negative and indicative of an exothermic process. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicated that the chemical sorption was the rate-limiting step, instead of mass transfer.     

Competitive Sorption of Arsenate and Phosphate on Aluminum Mining By-product

Studies concerning competitive sorption of anions on oxidic materials eligible to be used as soil amendments are crucial for a better understanding of the adsorbent??s effectiveness and ion mobility/availability in the environment. This study evaluated mono-/multi-element adsorption of phosphate and arsenate on aluminum (AMB) and iron mining by-products (IMB; used for comparison) and measured the effect of pH and thermal pretreatments on P and As adsorption on AMB and IMB. We also evaluated whether the desorption of As previously adsorbed on AMB and IMB increases with the addition of increasing doses of P. For adsorption, each adsorbent was reacted at selected pHs with solutions containing As and P individually or in combination. Non-competitive desorption was performed with 30?mmol?L^?1 NaCl. Arsenate displacement was evaluated by reaction of the adsorbents containing previously adsorbed As with P-containing solutions. The competition between P and As decreased the adsorption of these anions by 2.7 and 23.2?%, respectively. Increasing pH decreased adsorption of both As and P, whereas the thermal pretreatment increased P adsorption by 40?% and As adsorption by 15?%. Phosphate in solution increased As desorption, with each millimoles per kilogram of adsorbed P desorbing as much as 2.3?±?1.1?mmol?kg^?1 of As.     

Removal of Remazol Brilliant Blue Dye from Dye-Contaminated Water by Adsorption Using Red Mud: Equilibrium, Kinetic, and Thermodynamic Studies

Utilization of industrial solid wastes for the treatment of wastewater from another industry could help environmental pollution abatement, in solving both solid waste disposal as well as liquid waste problems. Red mud (RM) is a waste product in the production of alumina and it poses serious pollution hazard. The present paper focuses on the possibility of utilization of RM as an adsorbent for removal of Remazol Brilliant Blue dye (RBB), a reactive dye from dye-contaminated water. Adsorption of RBB, from dye-contaminated water was studied by adsorption on powdered sulfuric acid-treated RM. The effect of initial dye concentration, contact time, initial pH, and adsorbent dosage were studied. Langmuir isotherm model has been found to represent the equilibrium data for RBB?CRM adsorption system better than Freundlich model. The adsorption capacity of RM was found to be 27.8?mg dye/g of adsorbent at 40?°C. Thermodynamic analysis showed that adsorption of RBB on acid-treated RM is an endothermic reaction with ?H ⁰ of 28.38?kJ/mol. The adsorption kinetics is represented by second-order kinetic model and the kinetic constant was estimated to be 0.0105?±?0.005?g/mg?min. Validity of intra-particle diffusion kinetic model suggested that among the mass transfer processes during the dye adsorption process, pore diffusion is the controlling step and not the film diffusion. The process can serve dual purposes of utilization of an industrial solid waste and the treatment of liquid waste.     

Kinetic and Removal Mechanisms of Ethylbenzene from Contaminated Solutions by Chitin and Chitosan

In this study, the efficiency of chitin and chitosan toward the removal of ethylbenzene from aqueous solutions was investigated. Batch adsorption experiments of ethylbenzene-contaminated waters (5?C200 mg/L) were carried out to evaluate the removal performance. Ethylbenzene uptake was determined from the changes in concentration, as the residual concentration was measured by gas chromatography with mass spectroscopy. The results indicated that the adsorption of ethylbenzene by chitin and chitosan were in agreement with the Langmuir isotherm, for two parameters model, and Redlich?CPeterson isotherm, for three parameters model. A maximum removal percentage of 65% of ethylbenzene can be achieved using chitosan as adsorbent material. The adsorption capacity of ethylbenzene followed the order chitosan?>?chitin. The pseudo-second order rate model described best the adsorption kinetics of ethylbenzene for the two selected adsorbents. The kinetic studies also revealed that the pore diffusion is not the only rate controlling step in the removal of ethylbenzene. Overall, the study demonstrated that chitosan is a potential adsorbent for the removal of ethylbenzene at concentrations as high as 200 mg/L.     

Radiation Synthesis of Poly(Acrylamide-Acrylic Acid-Dimethylaminoethyl Methacrylate) Resin and Its Use for Binding of Some Anionic Dyes

Poly(acrylamide-acrylic acid-dimethylaminoethyl methacrylate) P(AAm-AA-DMAEMA) resin was prepared by the template copolymerization. PAAm was used as a template for the copolymerization of DMAEMA and AA in aqueous solution using gamma rays. The adsorption of indigo carmine and eriochrome black-T anionic dyes from aqueous media on P(AAm-AA-DMAEMA) has been investigated. The adsorption behavior of this resin has been studied under different adsorption conditions: dye concentrations (50?C500 mg l^?1), contact times, temperature (30?C55°C), and pH values (2?C7). The amount of dye adsorbed increased with increasing resin content, but it had a little change with temperature and decreased slightly with increasing pH. Adsorption data of the samples were modeled by the pseudo-first-order and pseudo-second-order kinetic equations in order to investigate dye adsorption mechanism. It was found that the adsorption kinetics of the resin followed a pseudo-second-order model with rate constant (k ₂) of 2.5?×?10^?3 and 1.8?×?10^?2 g (mg^?1 min^?1) for indigo carmine and eriochrome black-T, respectively. Equilibrium isotherms were analyzed using the Langmuir and Freundlich isotherms. It was seen that the Freundlich model fits the adsorption data better than the Langmuir model.     

Removal of Plant Pathogen Propagules from Irrigation Runoff using Slow Filtration Systems: Quantifying Physical and Biological Components

A novel high-capacity phosphate removal adsorbent of graphene nanosheets (GNS) supported lanthanum hydroxide (LaOH) is prepared. The phosphate adsorption performance for GNS-LaOH is examined by a batch adsorption method from aqueous solutions. The Freundlich and Langmuir models are used to simulate the sorption equilibrium, which reveal that the Langmuir model has a better correlation with the experimental data. The maximum adsorption capacity is calculated to be 41.96 mg/g. The kinetic data from the adsorption of phosphate is suggested as the pseudo-second-order model, and the multi-linearity adsorption process is observed in the intraparticle diffusion model, indicating that a chemisorption process is dominant in the adsorption of phosphate. The phosphate adsorption mechanism is explored by analyzing the Fourier transform infrared spectroscopy (FT-IR) and the relationship between the adsorption amount and the pH value of phosphate solution. Ligand exchange and electrostatic and Lewis acid–base interactions are determined to be three main factors for phosphate adsorption.     

Papaya (Carica papaya L.) Leaf Powder: Novel Adsorbent for Removal of Methylene Blue from Aqueous Solution

Batch sorption experiments were carried out to investigate the potentiality of papaya leaf powder (PLP) for the removal of methylene blue (MB) from aqueous solution. The effects of various experimental parameters, such as adsorbent dose, initial solution concentration, contact time, and solution pH were also studied. The amount of dye adsorbed was found to increase with increase in initial dye concentrations. Papaya leaf adsorbs MB better in basic medium. The adsorption equilibrium data fitted well in the Langmuir isotherm equation with a monolayer sorption capacity of 512.55?mg?g^?1. The kinetics of MB adsorption onto papaya leaf was examined using the pseudo-first and pseudo-second order and unified approach kinetic models. The adsorption kinetics followed the pseudo-second order kinetic model, but the rate constant was found to depend on initial dye concentration. The unified approach model described the equilibrium and kinetics well. The forward and backward rate constants were determined from the unified approach model.     

THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE

The adsorption isotherms (20°C) of phosphate on two potassium kaolinites and two aluminium oxides have been determined at pH values from 3 to 10 and at concentrations ranging from 10^?4 to 10^?2M. The reversibility of the adsorption with respect to pH and concentration has also been examined. The isotherms result from at least three types of adsorption site (regions I, II, and III) of widely different reactivities. The number of adsorption sites increases to a limit with decrease in pH for regions I and II. The behaviour of region III is more complex. The different adsorbents behave in essentially the same manner and differ only in the number of adsorption sites. It is tentatively suggested that regions I and II are located on an edge –Al(OH)₂ of the adsorbents, while region III results from penetration into some amorphous region of the crystal surface.