Removal of Congo Red from Aqueous Solutions by Spent Black Tea as Adsorbent

Herein we present spent black tea as an adsorbent for the removal of Congo red dye from aqueous solutions. The effects of various parameters such as pH, time, temperature, adsorbent dosage and adsorbate dosage on dye adsorption were investigated. Batch experiments were conducted using different amount of adsorbent material (2.5–1000 mg) at varying amounts of adsorbate (5–500 mg/L) at 35°C and different pH (1–13). A maximum dye removal of >80% was achieved with an adsorbent dose of 100 mg, adsorbate concentration of 5 mg/L under pH range of 6 within 5 min at room temperature. The experimental data were modeled by Langmuir, Freundlich and Temkin isotherms and conforms to both Langmuir and Freundlich isotherms but not to Temkin isotherm. The proposed spent black tea can be effectively used as a low cost adsorbent for the removal of Congo red dye.     

Reactive Red 120 dye removal from aqueous solution by adsorption on nano-alumina

The adsorption of Reactive Red 120 dye from aqueous solutions by using nano-alumina has been investigated. The batch adsorption studies were carried out to determine the impact of pH, contact time, concentration of dye, and the adsorbent dose on adsorption process. The maximum adsorption efficiency was observed at pH 3. However with an increase of the adsorbent dose, the dye removal efficiency increased, while the amount of dye adsorbed per unit mass (mg/g) decreased. A pseudo-second-order model best described the adsorption kinetics of the specified dye onto nano-alumina. In this case the Langmuir isotherm model appeared to be most suitable. Findings of the present study reveal that nano-alumina can be an effective adsorbent for the removal of Reactive Red 120 from aqueous solutions.     

Kinetics of a reactive dye adsorption onto dolomitic sorbents

A novel wastewater treatment technique has been investigated, for reactive dye removal, in batch kinetic systems. These experimental studies have indicated that charred dolomite has the potential to act as an adsorbent for the removal of Brilliant Red reactive dye from aqueous solution. The effect of initial dye concentration, adsorbent mass:liquid volume ratio, and agitation speed on dye removal have been determined with the experimental data mathematically described using empirical external mass transfer and intra-particle diffusion models. The experimental data show conformity with an adsorption process, with the removal rate heavily dependent on both external mass transfer and intra-particle diffusion.     

Removal of anionic dye Congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent: equilibrium, thermodynamic, kinetics, mechanism and process design

Pine cone a natural, low-cost agricultural by-product in Australia has been studied for its potential application as an adsorbent in its raw and hydrochloric acid modified form. Surface study of pine cone and treated pine cone was investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The modification process leads to increases in the specific surface area and decreases mean particle sizes of acid-treated pine cone when compared to raw pine cone biomass. Batch adsorption experiments were performed to remove anionic dye Congo red from aqueous solution. It was found that the extent of Congo red adsorption by both raw pine cone biomass and acid-treated biomass increased with initial dye concentration, contact time, temperature but decreased with increasing solution pH and amount of adsorbent of the system. Overall, kinetic studies showed that the dye adsorption process followed pseudo-second-order kinetics based on pseudo-first-order and intra-particle diffusion models. The different kinetic parameters including rate constant, half-adsorption time, and diffusion coefficient were determined at different physico-chemical conditions. Equilibrium data were best represented by Freundlich isotherm model among Langmuir and Freundlich adsorption isotherm models. It was observed that the adsorption was pH dependent and the maximum adsorption of 32.65 mg/g occurred at pH of 3.55 for an initial dye concentration of 20 ppm by raw pine cone, whereas for acid-treated pine cone the maximum adsorption of 40.19 mg/g for the same experimental conditions. Freundlich constant 'n' also indicated favourable adsorption. Thermodynamic parameters such as ?G(0), ?H(0), and ?S(0) were calculated. A single-stage batch absorber design for the Congo red adsorption onto pine cone biomass also presented based on the Freundlich isotherm model equation.     

Textile Wastewater Treatment With Activated Sludge And Powdered Activated Carbon

The objective of the study is to determine the effectiveness of batch activated sludge process and powdered activated carbon adsorption for organic and color removal from textile wastewaters. Factors affecting treatment performance investigated in the study included raw wastewater strength, various combinations of dye to starch in the wastewater, aeration time. Synthetic wastewaters using starch solution and disperse-red-60 dye were used in the adsorption study. The 3 wastewater strengths used included low, medium and high strength. The 5 different dye to starch combinations used included 0% dye+100% starch, 25% dye+75% starch, 50% dye+50% starch, 75% dye+25% starch, and 100% dye+0% starch. The batch bio-oxidation was conducted for a period of 24 hours. The COD removal efficiency, color removal, bio-oxidation rate constant, F/M ratio, SVI, pH and temperature were determined. The results indicated that starch was much easier to remove by the batch activated sludge process compared to disperse-red-60 dye, which was virtually non-biodegradable. Wastewaters containing 100% starch had the highest COD removal efficiency. Increase in dye concentration in wastewater resulted in decrease in the COD removal efficiency. The COD removal efficiency ranged from 6 to 45% for low strength wastewater of 100mg/L COD, 27 to 80% for medium strength wastewater of 500mg/L COD, and 23 to 65% for high strength wastewater of 1000mg/L COD. The low strength wastewaters had the best settling characteristics, while the medium strength wastewaters had the worst. For high PAC dosage of 15g/L, high COD removal efficiencies of 88 to 98% removal and E * ab of 36 to 47 were obtained. It is recommended that activated sludge be used to remove high COD organic pollutants first, followed by PAC adsorption to remove dye waste in the treatment of textile wastewaters.     

Application of 'waste' metal hydroxide sludge for adsorption of azo reactive dyes

The capacity and mechanism of metal hydroxide sludge in removing azo reactive dyes from aqueous solution was investigated with different parameters, such as charge amount of dyes, system pH, adsorbent particle size, and adsorbent dosage. The three anionic dyes used were CI Reactive Red 2, CI Reactive Red 120, and CI Reactive Red 141, increasing in number of sulfonic groups, respectively. Only 0.2% (w/v) of powdered sludge (<75microm) achieved color removal from 30 mg l(-1) reactive dye solutions within 5 min without pH adjustment. The larger the charge amount of the dyes, the greater the adsorption (>90%) on the metal hydroxide sludge. The system pH played a significant role in the adsorption on metal hydroxides and formation of dye-metal complexes. The optimum system pH for dye adsorption was 8-9 which was close to the pH(zpc) of the sludge while the precipitation of dye-metal complexes occurred at system pH 2. The maximum adsorption capacity (Q degrees ) of the sludge for the reactive dyes was 48-62 mg dye g(-1) adsorbent. The Langmuir and Freundlich models showed that the higher charged dyes had a higher affinity of adsorption. The smaller particle size and the greater amount of adsorbent showed the faster process, due to an increase in surface area of adsorbent. Desorption studies elucidated that metal hydroxide sludge had a tendency for ion exchange adsorption of sulfonated azo reactive dyes. Leaching data showed that the treated water was nontoxic at a system pH above 5 or a solution pH above 2.     

An approach to textile dye removal using sawdust from Aspidosperma polyneuron

The textile industry is responsible for discarding wastewater contaminated with dyes. The timber industry generates waste in the form of sawdust. The aim of the present study was to evaluate the adsorptive potential of sawdust obtained from the Aspidosperma polyneuron tree for the removal of the textile dye from wastewater. Sawdust was subjected to different pre-treatments (acid, alkaline and polyethyleneimine) in order to increase its adsorption capacity. Based on the results from the isotherms, treatment with polyethyleneimine (PEI) led to the greatest adsorption capacity and fits the Freundlich model, indicating cooperative adsorption. Other treatments with sawdust best fit the Langmuir model, but the untreated sawdust presented better results than the treated sawdust. These results were only surpassed by sawdust treated with PEI. A. polyneuron revealed good potential for use as an adsorbent to remove dyes, which is a novel result, since to date there is no study on its use as a sorbent material.     

Novel heterocyclic chitosan‐based Schiff base: evaluation as adsorbent for removal of methyl orange from aqueous solution

A Schiff base has been made by reacting chitosan with 2‐hydroxy quinoline‐3‐carbaldehyde in the presence of acetic acid. The synthesized compound was characterized by FTIR, TGA, XRD and SEM techniques. The Schiff base was evaluated for removal of anionic dye from aqueous solution using methyl orange as model dye. Influences of initial dye concentration, pH and contact time on the extent of adsorption were investigated. The adsorption data fits best with Freundlich isotherm model and the maximum adsorption capacity was found to be 55.55 mg/g. The kinetic study indicated second‐order adsorption. The thermodynamic parameters showed the adsorption to be endothermic and non‐spontaneous. Desorption studies indicated the reusability of the compound as adsorbent material.     

Removal of mercury(II) from aqueous solutions and chlor-alkali industry wastewater using 2-mercaptobenzimidazole-clay

The 2-mercaptobenzimidazole loaded natural clay was prepared for the removal of Hg(II) from aqueous media. Adsorption of the metal ions from aqueous solution as a function of solution concentration, agitation time, pH, temperature, ionic strength, particle size of the adsorbent and adsorbent dose was studied. The adsorption process follows a pseudo-second-order kinetics. The rate constants as a function of initial concentration and temperature were given. The adsorption of Hg(II) increased with increasing pH and reached a plateau value in the pH range 4.0-8.0. The removal of Hg(II) was found to be >99% at an initial concentration of 50 mg/l. Mercury(II) uptake was found to increase with ionic strength and temperature. Further, the adsorption of Hg(II) increased with increasing adsorbent dose and decrease with adsorbent particle size. Sorption data analysis was carried out using Langmuir and modified Langmuir isotherms for the uptake of metal ion in an initial concentration range of 50-1,000 mg/l. The significance of the two linear relationships obtained by plotting the data according to the conventional Langmuir equation is discussed in terms of the binding energies of the two population sites involved which have a widely differing affinity for Hg(II) ions. Thermodynamic parameters such as changes of free energy, enthalpy, and entropy were calculated to predict the nature of adsorption. It was found that the values of isosteric heat of adsorption were varied with surface loading. The chlor-alkali industry wastewater samples were treated by MBI-clay to demonstrate its efficiency in removing Hg(II) from wastewater.     

Adsorption of basic dyes on granular activated carbon and natural zeolite

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.     

Removal of Lissamine Red From Wastewater Using Waste Materials

Feasibility of a waste material, flyash, as a material for purification of wastewater containing Lissamine Red has been studied. Effects of time and concentration, temperature and pH on the removal of the dye have been studied. Lower concentrations favour the uptake of dye from water and the maximum removal was observed at a dye concentration of 20 mgL m 1 , 30°C, pH of 7 and adsorbent particle size of 53 µm. Dynamics of the uptake was studied using Lagergren's equation. The mass transfer coefficient was found to be 0.05 cmmin m 1 at a concentration of 20 mgL m 1 , 30°C and 53 µm particle size.     

Removal of lindane and malathion from wastewater using bagasse fly ash--a sugar industry waste

The bagasse fly ash, obtained from the local sugar industry, has been used as inexpensive and effective adsorbent for the removal of lindane and malathion from wastewater. The optimum contact needed to reach equilibrium was found to be 60 min. Maximum removal takes place at pH 6.0. The removal of the pesticides increases with an increase in adsorbent dose and decreases with adsorbent particle size. The optimum adsorbent dose is 5 g/l of particle size 200-250 microm. Removal of the two pesticides was achieved up to 97-98% under optimum conditions. The material exhibits good adsorption capacity and follows both Langmuir and Freundlich models. Thermodynamic parameters also indicate the feasibility of the process. The adsorption was found to be exothermic in nature. At lower concentrations, adsorption is controlled by film diffusion, while at higher concentrations, it is controlled by particle diffusion mechanisms. The adsorbent is a very useful and economic product for the removal of lindane and malathion.     

Equilibrium studies during the removal of dyestuffs from aqueous solutions using Bagasse pith

The adsorption of four dyestuffs, namely, Basic Blue 69 (BB69), Basic Red 22 (BR22), Acid Red 114 (AR114) and Acid Blue 25 (AB25), onto bagasse pith has been studied. Bagasse pith is a cheap, abundant waste product from the sugar industry in Egypt and was found to have the following monolayer equilibrium saturation capacities: 158, 77, 23 and 22 mg dye g⁻¹ pith.

The effects of pith particle size range and dye solution temperature were studied. The equilibrium data were analysed using Langmuir, Freundlich and Jossens isotherms.     

Preparation of layered double hydroxides using boron mud and red mud industrial wastes and adsorption mechanism to phosphate

Phosphate removal was important for wastewater treatment, and adsorption was an efficient treatment process. In this study, the layered double hydroxide adsorbent (BR‐LDH), which was prepared under alkali conditions using industrial residues boron mud and red mud, was used to adsorb the phosphate. The prepared BR‐LDH was characterised by X‐ray diffraction, Scanning electron microscopy, Energy‐dispersive X‐ray spectroscopy, and Thermo‐gravimetric‐differential thermal analysis. Adsorption experiments were carried out as a function of dosage, contact time, temperature and initial pH of phosphate solution. The removal ratio of phosphate onto OBR‐LDH reached 93%. The adsorption data showed a good compliance with the pseudo‐second‐order kinetic model. In addition, the mineral composition, the functional groups, the valence of elements and zeta potentials of OBR‐LDH before and after adsorption were used to analyse the adsorption mechanism. The result of real wastewater suggested that OBR‐LDH was excellent adsorbent for phosphorus removal from actual wastewater.     

Study on the adsorption of Neutral Red from aqueous solution onto halloysite nanotubes

Halloysite nanotubes (HNTs), a low-cost available clay mineral, were tested for the ability to remove cationic dye, Neutral Red (NR), from aqueous solution. Natural HNTs used as adsorbent in this work were initially characterized by XRD, FT-IR, TEM and BET. The effect of adsorbent dose, initial pH, temperature, initial concentration and contact time were investigated. Adsorption increased with increase in adsorbent dose, initial pH, temperature and initial concentration. The equilibrium data were well described by both the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 54.85, 59.24 and 65.45 mg/g at 298, 308 and 318 K, respectively. Batch kinetic experiments showed that the adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.999. Thermodynamic parameters of ΔG⁰, ΔH⁰ and ΔS⁰ indicated the adsorption process was spontaneous and endothermic. The results above confirmed that HNTs had the potential to be utilized as low-cost and relatively effective adsorbent for cationic dyes removal.     

Phosphorus immobilisation in Al‐drinking water treatment sludge (Al‐DWTS) and soil under laboratory conditions

This study assessed the potential reuse of an aluminium coagulated drinking water treatment sludge (Al‐DWTS) as a main substrate in constructed wetland to replace soil for the treatment of P‐enriched wastewater. The adsorption isotherm and kinetics of phosphorus (P) removal from high‐P solution by Al‐DWTS and a local soil from Bailieborough, Ireland, were studied and compared. The P adsorption process was examined as a function of contact time, initial P concentration, pH and temperature. Data of P adsorption were well fitted to the Langmuir and the Freundlich isotherms but the Freundlich isotherm had a higher correlation coefficient. The P adsorption capacity on the Al‐DWTS and the soil tended to increase with an increase in temperature. The maximum P adsorption capacity of the Al‐DWTS and the soil was 39.4 mg P mg^?1 and 9.5 mg P mg^?1, respectively, at conditions of pH of 4.0 and temperature of 23°C. Kinetics studies show that adsorption in both cases followed pseudo‐second‐order kinetics. The fact that the Al‐DWTS exhibited a significantly higher P adsorption capacity at high P solution compared with the soil suggests that Al‐DWTS can be a ‘novel‐waste’ bioadsorbent with promising application in wastewater treatment engineering, such as constructed wetland systems.     

Biosorption of chromium(VI) from aqueous solutions by green algae Spirogyra species.

Biosorption of heavy metals is an effective technology for the treatment of industrial wastewaters. Results are presented showing the sorption of Cr(VI) from solutions by biomass of filamentous algae Spirogyra species. Batch experiments were conducted to determine the adsorption properties of the biomass and it was observed that the adsorption capacity of the biomass strongly depends on equilibrium pH. Equilibrium isotherms were also obtained and maximum removal of Cr(VI) was around 14.7 x 10(3) mg metal, kg of dry weight biomass at a pH of 2.0 in 120 min with 5 mg/l of initial concentration. The results indicated that the biomass of Spirogyra species is suitable for the development of efficient biosorbent for the removal and recovery of Cr(VI) from wastewater.     

The evaluation of low‐cost biosorbents for removal of an azo dye from aqueous solution

There is a need to develop innovative and alternative technologies that can remove dyes from wastewater. In this study, low‐cost and locally available two renewable biosorbents (cotton stalk and apricot seed) were investigated to remove of Astrazone Black from aqueous solution. The effects of various experimental parameters such as dye concentration, adsorbent amount, adsorbent particle size and initial pH were tested, and optimal experimental conditions were examined. The results showed that as the amount of adsorbent was increased, the percentage of dye removal increased accordingly. The ratios of dye sorbed increased as the adsorbent particle size decreased. In addition, antibacterial effect of untreated and treated (decolourized) dye on a soil bacterium, Pseudomonas aeruginosa, was determined. The removal of this dye with agricultural wastes reduced the toxic effect on P. aeruginosa. This reduction in toxic effect is important both in respect of environmental biotechnology and waste detoxification.     

Synthetic polymers and their blends for removing lead from aqueous solutions

The article has investigated main commodity synthetic polymers (polyethylene terephthalate(PETP), polyethylene (PE) and polystyrene (PS) and their blends designed for adsorption of lead ions from wastewaters. Blends were prepared by extrusion from the melt at PS concentration from 5 to 20 fraction of total mass, %. The time of attaining equilibrium at adsorption of lead ions on the polymer surface has been found. The obtained data indicate that polymers in question were more efficient compared with others, which investigated for assessing their adsorption ability with respect to lead ions. Results of equilibrium isothermal adsorption of lead ions on the mixed PETP/PS system point out that at an increase of percent content of PS in the blend a substantial increase of adsorbed lead is achieved per unit weight of polymer adsorbent. This correlates with the type and dimensions of interface morphology of blends.     

Continuous water treatment by adsorption and electrochemical regeneration

This study describes a process for water treatment by continuous adsorption and electrochemical regeneration using an air-lift reactor. The process is based on the adsorption of dissolved organic pollutants onto an adsorbent material (a graphite intercalation compound, Nyex^®1000) and subsequent electrochemical regeneration of the adsorbent leading to oxidation of the adsorbed pollutant. Batch experiments were carried out to determine the adsorption kinetics and equilibrium isotherm for adsorption of a sample contaminant, the organic dye Acid Violet 17. The adsorbent circulation rate, the residence time distribution (RTD) of the reactor, and treatment by continuous adsorption and electrochemical regeneration were studied to investigate the process performance. The RTD behaviour could be approximated as a continuously stirred tank. It was found that greater than 98% removal could be achieved for continuous treatment by adsorption and electrochemical regeneration for feed concentrations of up to 300 mg L⁻¹. A steady state model has been developed for the process performance, assuming full regeneration of the adsorbent in the electrochemical cell. Experimental data and modelled predictions (using parameters for the adsorbent circulation rate, adsorption kinetics and isotherm obtained experimentally) of the dye removal achieved were found to be in good agreement.