Removal of nickel from aqueous solutions using crab shells

Partially converted crab shell waste, which contains chitosan, was used to remove nickel from water. The chelating ability of chitosan makes it an excellent adsorbent for removing pollutants. Advantages of chitosan in crab shells include availability, low cost, and high biocompatibility. The metal uptake by partially converted crab shell waste was successful and rapid. The sorption occurred primarily within 5 min. The sorption mechanism appears to be quite complicated and cannot be adequately described by either the Langmuir or Freundlich theories. Various anions, including chloride, bromide, fluoride, acetate, sulfate, nitrate, and phosphate, were found to have a very small effect on the capacity of the crab shells for uptake of nickel. The effect of pH was also found not to be prominent.     

Removal of Pb(II) ions from aqueous solution by adsorption using bael leaves (Aegle marmelos)

Biosorption of Pb(II) on bael leaves (Aegle marmelos) was investigated for the removal of Pb(II) from aqueous solution using different doses of adsorbent, initial pH, and contact time. The maximum Pb loading capacity of the bael leaves was 104 mg g^?1 at 50 mg L^?1 initial Pb(II) concentration at pH 5.1. SEM and FT-IR studies indicated that the adsorption of Pb(II) occurs inside the wall of the hollow tubes present in the bael leaves and carboxylic acid, thioester and sulphonamide groups are involved in the process. The sorption process was best described by pseudo second order kinetics. Among Freundlich and Langmuir isotherms, the latter had a better fit with the experimental data. The activation energy E_a confirmed that the nature of adsorption was physisorption. Bael leaves can selectively remove Pb(II) in the presence of other metal ions. This was demonstrated by removing Pb from the effluent of exhausted batteries.     

Removal of Ni(II) ions from aqueous solutions using waste of tea factory: adsorption on a fixed-bed column

The removal efficiency of waste tea from nickel containing aqueous solutions was investigated. All experiments were conducted fixed-bed columns. Experiments were carried out as a function of liquid flow rate (5-20 mL/min), initial Ni(II) concentration (50-200 mg/L), bed height (10-30 cm), pH of feed solution (2.0-5.0) and particle size (0.15-0.25 to 1.0-3.0 mm) of adsorbent. The total adsorbed quantities, equilibrium uptakes and total removal percents of Ni(II) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates, different inlet Ni(II) concentrations, different pH value, different bed height and different particle size for waste tea. The longest breakthrough time and maximum of Ni(II) adsorption is obtained at pH 4.0. Decrease in the particle size from 1.0-3.0 to 0.15-0.25 mm resulted in significant increase in the treated volume, breakthrough time and bed capacity. The results show that the column performed well at lowest flow rate. Also, column bed capacity and exhaustion time increased with increasing bed height. When the initial Ni(II) concentration is increased from 50 to 200 mg/L, the corresponding adsorption bed capacity appears to increase from 7.31 to 11.17 mg/g. The bed depth service time (BDST) model and the Thomas model were used to analyze the experimental data and the model parameters were evaluated. Good agreement of the experimental breakthrough curves with the model predictions was observed.     

Removal of Pb(II) from aqueous solution using modified and unmodified kaolinite clay

Modified kaolinite clay with 25% (w/w) aluminium sulphate and unmodified kaolin were investigated as adsorbents to remove Pb(II) from aqueous solution. The results show that amount of Pb(II) adsorbed onto modified kaolin (20 mg/g) was more than 4.5-fold than that adsorbed onto unmodified kaolin (4.2 mg/g) under the optimized condition. In addition, the linear Langmuir and Freundlich models were used to describe equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The kinetic adsorption of modified and unmodified kaolinite clay fitted well to the pseudo-second-order model. Furthermore, both modified and unmodified kaolinite clay were characterized by X-ray diffraction, Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). Finally, both modified and unmodified kaolinite clay were used to remove metal ions from real wastewater, and results show that higher amount of Pb(II) (the concentration reduced from 178 to 27.5 mg/L) and other metal ions were removed by modified kaolinite clay compared with using unmodified adsorbent (the concentration reduced from 178 to 168 mg/L).     

Removal of fluoride ions from aqueous solution at low pH using schwertmannite

Wastewater containing fluoride requires polishing after precipitation/coagulation treatment in order to meet stringent environmental legislation. Accordingly, adsorption characteristics of fluoride onto schwertmannite adsorbent were studied in a batch system with respect to changes in initial concentration of fluoride, equilibrium pH of sample solution, adsorbent dosage and co-existing ions. Equilibrium adsorption data were obtained at 295.6, 303 and 313 K, and are interpreted in terms of two-site Langmuir, Freundlich, Langmuir-Freundlich, Redlich-Peterson, Tóth and Dubinin-Radushkevitch isotherm models. The experimental and equilibrium modeling results revealed that the capacity of schwertmannite for fluoride is high but insensitive to changes in solution temperature. An increase in equilibrium pH of sample solution reduced significantly the fluoride removal efficiency. In binary component systems, inner-sphere complex forming species had negative effects on fluoride adsorption while outer-sphere complex forming species improved slightly the fluoride removal efficiency. The schwertmannite adsorbent was regenerable and had the ability to lower the fluoride concentration to acceptable levels.     

Removal of fluoride from aqueous solution using granular acid-treated bentonite (GHB): batch and column studies

Removal of fluoride from aqueous solution using granular acid-treated bentonite (GHB) was studied by batch and column adsorption experiments. The results of the batch adsorption experiments demonstrated that the maximum fluoride removal was obtained at pH of 4.95 and it took 40 min to attain equilibrium. Kinetics data fitted pseudo-second-order model. Batch adsorption data was better described by Redlich-Peterson and Freundlich isotherm models than Langmuir isotherm model. The adsorption type of GHB was ion exchange. Column experiments were carried out at different influent fluoride concentrations and different flow rates. The capacities of the breakthrough and exhaustion points increased with the decrease of flow rate and the increase of initial fluoride concentration. The experimental results were well fitted with Thomas model. Exhausted GHB was regenerated by alkali/alum treatment. The total sorption capacity of GHB was increased after regeneration and activation.     

Removal of copper ions from aqueous solutions by hazelnut shell

There is a great potential of woody hazelnut shell to use in some applications. Sorption studies are one of these. For this reason in this paper, batch adsorption of Cu(2+) ions onto hazelnut shells was studied. The capacity of the adsorption for the removal of copper ions from aqueous solution was investigated under different conditions such as solution contact time (1-360 min), particle size (0-75, 75-150 and 150-200 microm), temperature of solution (25-60 degrees ) and solution pH (3-7). Moreover, zeta potential of particles at different initial pHs (2-10) was measured. The equilibrium data were processed according to Langmuir and Freundlich's models and higher adsorption capacity values towards Cu(2+) ions were shown. The adsorption kinetics was investigated and the best fit was achieved by a second-order equation.     

Biosorption of copper(II) and lead(II) from aqueous solution by chaff in a fixed-bed column

In this article, the ability of chaff to adsorb heavy metal ions from aqueous solution was investigated in a fixed-bed column. The effect of important parameters, such as the value of pH, the flow rate, the influent concentration of solution and the effect of coexistence ions, was studied. Also the adsorption/desorption recycles of chaff were shown, and the results indicated that chaff could be recycled to remove heavy metal ions. The Thomas model was applied to adsorption of copper and lead at different flow rate and different influent concentration to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The model was found suitable for describing the biosorption process of the dynamic behavior of the chaff column. All the results suggested that chaff as adsorbent to removal heavy metal ions from solution prove efficient, and the rate of biosorption process is speedy. Furthermore, the efficiency of adsorption is high. When the flow rate was 3.6 ml min(-1) and the influent concentration of copper and lead was 14.82 mg l(-1) and 50.12 mg l(-1) respectively, the equilibrium adsorption biomass reached 1.98 mg g(-1) and 6.72 mg g(-1), respectively. The competitive adsorption for lead and copper was studied. Moreover the total adsorbing capability of chaff did not decrease when there were both copper(II) and lead(II) in solution.     

Removal of naphthalene in Brij 30-containing solution by ozonation using rotating packed bed

The removal efficiency of polycyclic aromatic hydrocarbons (PAHs) by ozonation using a rotating packed bed (RPB) in the surfactant-containing solution is studied. As an ozonation process starts, the ozone-containing gas is introduced and transferred into to the solution. The target PAHs in the solution would be then eliminated via both the gas stripping and ozonation decomposition. The RPB, which provides high gravitational force by adjusting the rotational speed, is employed as a novel ozone contactor. The naphthalene (NAP) and Brij 30 are chosen as the model pollutant and surfactant. Note that the experiments with different concentrations of NAP, Brij 30, and inlet gas ozone are performed for the further investigation. The residual NAP, effluent dissolved oxygen and ozone, and off-gas ozone concentrations are simultaneously monitored. As a result, the removal of NAP in the RPB is remarkably efficient compared with the convectional contactors because of its greater mass transfer coefficient. Moreover, the removal efficiency of NAP is found significantly dependent on the concentrations of NAP, Brij 30, and inlet gas ozone. It takes about several minutes to reach the steady state under the conditions of this study. In addition, it suggests employing RPBs as ozone contacting devices for the high removal efficiency of NAP. Consequently, the present study is useful for the practicable understanding of application of RPBs for the ozonation of PAHs in surfactant-containing solution.     

Biosorption of lead(II) and cadmium(II) by protonated Sargassum glaucescens biomass in a continuous packed bed column

Biosorption of lead(II) and cadmium(II) from aqueous solutions by protonated Sargassum glaucescens biomass was studied in a continuous packed bed column. The selective uptake of Pb2+ and Cd2+ was investigated in a binary system with initial concentration of 1 mM for each metal ion. The selective uptake capacities of Pb2+ and Cd2+ at complete exhaustion point were obtained 1.18 and 0.22 mmol/g, respectively; therefore, the biosorbent showed much higher relative affinity for Pb2+ than for Cd2+. The optimum range of empty bed contact time (EBCT) was identified as 5-10 min in the packed bed column. The efficiency of biosorbent regeneration by 0.1 M HCl was achieved about 60%, so that the maximum uptake capacity of Pb2+ by the regenerated biomass was determined to be 0.75 mmol/g while the same value for the original biomass was 1.24 mmol/g. The Thomas model was found in a suitable fitness with the experimental data (R2 > 0.90 and % < 50%) at all different operation stages. Monitoring of pH in the effluent of the column presented the simultaneous release of H+ with the uptake of heavy metals; hence, ion exchange was confirmed to be one of the main biosorption mechanisms.     

Removal of copper(II) from aqueous solution by Jordanian pottery materials

The aim of this work was to assess the possibility of removing some heavy metals from water by a low-cost adsorbent, like Jordanian raw pottery. Five types of raw and modified pottery materials have been investigated. The effects of initial metal concentration, agitation time, pH and temperature on the removal of Cu(II) were studied. A pseudo-first order was used to test the adsorption kinetics. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The effect of solution pH on the adsorption onto pottery was studied in the pH range 1-5. The adsorption was exothermic at ambient temperature and the computation of the parameters, DeltaH, DeltaS and DeltaG, indicated the interactions to be thermodynamically favorable.     

Continuous adsorption of lead ions in a column packed with palm shell activated carbon

The continuous adsorption of lead ions from aqueous solution on commercial, granular, unpretreated palm shell activated carbon (PSAC) was studied. Effect of pH, flow rates and presence of complexing agents (malonic and boric acids) were examined. The breakthrough period was longer at pH 5 indicating higher adsorption capacity of lead ions at higher pH. Increase of the flow rate, expectedly, resulted in the faster saturation of the carbon bed. Presence of complexing agents did not improve adsorption uptake of lead ions. However, presence of malonic acid resulted in smoother pH stabilization of solution compared to single lead and lead with boric acid systems. The results on continuous adsorption of lead were applied to the model proposed by Wang et al. [Y.-H. Wang, S.-H. Lin, R.-S. Juang, Removal of heavy metals ions from aqueous solutions using various low-cost adsorbents, J. Hazard. Mater. B 102 (2003) 291–302]. The agreement between experimental and modelled breakthrough curves was satisfactory at both pHs.     

Removal and recovery of nickel(II) from aqueous solution by loofa sponge-immobilized biomass of Chlorella sorokiniana: characterization studies

The biosorption process for the removal of nickel(II) by loofa sponge-immobilized biomass of Chlorella sorokiniana (LIBCS), a newly developed immobilized biosorbent, was characterized. Effects of environmental factors on metal uptake capacity of LIBCS were studied and compared with free biomass of C. sorokiniana (FBCS). Nickel(II) removal by LIBCS was found to be influenced by pH of the solution, initial metal concentration, and biomass concentration. The biosorption of nickel(II) ions by both LIBCS and FBCS increased as the initial concentration of nickel(II) ions increased in the medium. No loss to biosorption capacity of LIBCS for nickel(II) was found due to the presence of loofa sponge, indeed as compared to FBCS an increase of 25.3% was noted in the biosorption capacity of LIBCS. Maximum biosorption capacities for FBCS and LIBCS were found as 48.08 and 60.38 mg nickel(II)/g, respectively, whereas the amount of nickel(II) ions adsorbed on the plain loofa sponge was 6.1mg/g. During these biosorption studies, LIBCS exhibited excellent physical and chemical stability without any significant release/loss of microalgal biomass from loofa sponge matrix. The kinetics of nickel(II) removal was extremely fast reaching at equilibrium in about 15 min for LIBCS and 20 min for FBCS. The biosorption equilibrium was well described by the Langmuir and Freundlich adsorption isotherms. The biosorption capacities were found to be solution pH dependent and the maximum adsorption was found at a solution pH 4-5. The LIBCS could be regenerated using 75 mM HCl, with up to 98% recovery. The LIBCS were shown to be robust and stable with little decrease in the nickel(II) uptake capacity when used in consecutive seven biosorption-desorption cycles. Continuous removal of nickel(II) from electroplating effluent by LIBCS packed in fixed bed column bioreactor confirm the possibility of developing a biological treatment process for the removal of toxic metals from authentic wastewater.     

Removal of Cu(II) from aqueous solution by adsorption onto acid-activated palygorskite

A series of activated palygorskite clay by HCl with different concentrations was prepared and applied as adsorbents for removal of Cu(II) from aqueous solutions. The effects of contact time, adsorbent dosages and pHs of suspension on the adsorption capacities for Cu(II) were investigated. The results showed that adsorption capacity of activated palygorskites increased with increasing the HCl concentration and the maximum adsorption capacity with 32.24 mg/g for Cu(II) is obtained at 12 mol/L of HCl concentration. The variations in IR spectra and pH of solution after adsorption Cu(II) confirmed that the numerous amount of silanol groups (Si-OH) originated by acid treatment were mainly responsible for Cu(II) adsorption onto acid-activated palygorskite. Kinetic studies indicated that the adsorption mechanisms in the Cu(II)/acid-activated palygorskite system followed the pseudo-second-order kinetic model with a relatively small contribution of film diffusion. Equilibrium data fitted well with Freundlich isotherm model compared to Langmuir isotherm model, indicating that adsorption takes place on heterogeneous surfaces of the acid-activated palygorskite. Adsorption-desorption studies presented that activated palygorskite has lower adsorption and desorption efficiencies using Cu(CH3COO)2 than that of other inorganic copper salts, such as CuSO4, Cu(NO3)2, and CuCl2.     

Removal of Pb(II) from aqueous solution by oxidized multiwalled carbon nanotubes

Oxidized multiwalled carbon nanotubes (MWCNTs) were employed as sorbent to study the sorption characteristic of Pb(II) from aqueous solution as a function of contact time, pH, ionic strength, foreign ions, and oxidized MWCNTs' contents under ambient conditions using batch technique. The results indicate that sorption of Pb(II) on oxidized MWCNTs is strongly dependent on pH values, and independent of ionic strength and the type of foreign ions. The removal of Pb(II) to oxidized MWCNTs is rather quickly and the kinetic sorption can be described by a pseudo-second-order model very well. Sorption of Pb(II) is mainly dominated by surface complexation rather than ion exchange. The efficient removal of Pb(II) from aqueous solution is limited at pH 7-10. X-ray photoelectron spectroscopy (XPS) is performed to study the sorption mechanism at a molecular level and thereby to identify the species of the sorption processes. The 3-D relationship of pH, Ceq and q indicates that all the data of Ceq-q lie in a straight line with slope -V/m and intercept C0V/m for the same initial concentration of Pb(II) and same content of oxidized MWCNTs of each experimental data.     

Removal of nickel from aqueous solution by the bacterium Bacillus thuringiensis

The biosorption of the toxic metal (nickel) from aqueous solutions on dried vegetative cell and spore-crystal mixture of Bacillus thuringiensis var. thuringiensis was tested under laboratory conditions as a function of pH, initial metal ion concentration and temperature. The characteristics of the adsorption process were investigated using Scatchard analysis. Scatchard analysis of the equilibrium binding data for metal ions on vegetative cell and spore-crystal mixture of B. thuringiensis gave rise to a linear plot, indicating that the Langmuir model could be applied successfully. Adsorption behaviour of nickel(II) ion on B. thuringiensis is expressed by both Langmuir and Freundlich isotherms. The adsorption data with respect to the metal provided an excellent fit to both isotherms. Ni(II) ion uptake of B. thuringiensis's spore-crystal mixture at 250 mg l(-1) was 15.7%, whereas its vegetative cell metal uptake was 10%. The best temperature for ion uptake was found to be at 35 degrees C.     

Removal of Pb(II) ions from aqueous solutions by sulphuric acid-treated wheat bran

Sulphuric acid-treated wheat bran (STWB) was used as an adsorbent to remove Pb(II) ions from aqueous solution. It was observed that the adsorption yield of Pb(II) ions was found to be pH dependent. The equilibrium time for the process was determined as 2h. STWB gave the highest adsorption yield at around pH 6.0. At this pH, adsorption percentage for an initial Pb(II) ions concentration of 100mg/L was found to be 82.8 at 25 degrees C for contact time of 2h. The equilibrium data obtained at different temperatures fitted to the non-linear form of Langmuir, Freundlich and Redlich-Peterson and linear form of Langmuir and Freundlich models. Isotherm constants were calculated and compared for the models used. The maximum adsorption capacity (q(max)) which was obtained linear form of Langmuir model increased from 55.56 to 79.37mg/g with increasing temperature from 25 to 60 degrees C. Similar trend was observed for other isotherm constants related to the adsorption capacity. Linear form of Langmuir isotherm data was evaluated to determine the thermodynamic parameters for the process. Thermodynamic parameters show that adsorption process of Pb(II) ions is an endothermic and more effective process at high temperatures. The pseudo nth order kinetic model was successfully applied to the kinetic data and the order (n) of adsorption reaction was calculated at the range from 1.711 to 1.929. The values of k(ad) were found to be 5.82x10(-4) and 21.81x10(-4)(min(-1))(mg/g)(1-n) at 25 and 60 degrees C, respectively. Activation energy was determined as 29.65kJ/mol for the process. This suggest that the adsorption Pb(II) ions by STWB is chemically controlled.     

Adsorption of nickel(II) from aqueous solution onto activated carbon prepared from almond husk

Activated carbon was prepared from almond husk by activating without (MAC-I) and with (MAC-II) H(2)SO(4) at different temperatures. The ability of the activated carbon to remove nickel(II) ions from aqueous solutions by adsorption has been investigated under several conditions such as pH, carbonisation temperature of husk, initial concentration of metal ions, contact time, and adsorbent concentration. Optimal conditions were pH 5.0, the carbonisation temperature of 700 degrees C, 50 min of contact time and adsorbent concentration of 5 g/l. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon, prepared from almond husk at 700 degrees C, through the addition of H(2)SO(4). The removal of Ni(II) were found to be 97.8% at initial concentration of 25mg/l and the adsorbent concentration of 5 g/l. When the adsorbent concentration was increased up to 40 g/l, the adsorption density decreased from 4.89 to 0.616 mg/g for MAC-II. In the isotherm studies, the experimental adsorption data fitted reasonably well the Langmuir isotherm for both MAC-I and MAC-II.     

Removal of Cu(II) ions by activated poplar sawdust (Samsun clone) from aqueous solutions

In this work, adsorption of Cu(II) ions on sawdust (SD) and activated sawdust (ASD) has been studied by using batch adsorption techniques. The equilibrium adsorption level was determined to be a function of the pH, initial Cu(II) concentration, and adsorbent dosage. The equilibrium nature of Cu(II) adsorption has been described by the Freundlich and Langmuir isotherms. The experimental adsorption data were fitted to the Langmuir adsorption model both sawdust and activated sawdust. The equilibrium capacity of sawdust and activated sawdust were 5.432 and 13.495 mg copper per g adsorbent, respectively at room temperature and natural pH. The maximum adsorption capacity was obtained at the maximum zeta potential value that -74.5 mV (pH 5) for activated sawdust and at -48.4 mV (pH 4) for sawdust. It was observed that activated sawdust was a suitable adsorbent than sawdust for removal of Cu(II) from aqueous solutions.     

Removal of chromium (VI) from aqueous solution using treated oil palm fibre

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.