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Three solutions to the film surface diffusion mass transport model are discussed. The solutions are based on the homogenous surface diffusion model (HSDM) and are compared using three different adsorption systems. The mass transport solutions include a Crank–Nicholson implicit finite difference method, a semi-analytical solution method and a Cartesian collocation method. The three solutions are compared for accuracy, stability, convergence and computation CPU time.The experimental systems used two adsorbents, activated carbon, a mainly microporous material, and sorbsil silica, a mainly macroporous material. Two categories of adsorbates were selected for the study, phenol, a relatively small organic molecule, which does not ionise, and basic dyes, larger organic structures, which exist as ionisable salts. A range of initial adsorbate concentrations were studied. The range of material types and experimental conditions selected should be sufficient to test and compare the three models under a variety of conditions. [Copyright &y& Elsevier]

Highlights: [•] A novel method was introduced by integrating magnetic field exposure with adsorption technique. [•] Combined magnetic field and adsorption process has a vital role in treating POME. [•] Adsorption performance and adsorption rate could be enhanced by magnetic field. [•] Magnetization process accelerated the removal of colour, TSS and COD in adsorption process. [•] The new method increased the percentage removal of colour, TSS and COD by 39%, 61% and 46% respectively. [Copyright &y& Elsevier]

Abstract: A feasibility study has been carried out on the preliminary process design of the production of activated carbon from the bamboo scaffolding waste based on 30tonnes of bamboo waste per day throughput. A comparison of the process economics of the stand-alone bamboo carbonization plant with a plant that is integrated into another major processing facility has been studied. The preliminary process design was based on various literature sources and an economic evaluation, in which the total capital investment (TCI), the production cost, the return on investment (ROI), the cash flow and the internal rate of return (IRR) of the stand-alone plant and integrated plant were estimated. The TCI of the stand-alone plant and integrated plant are HK$ 7,430,000 and HK$ 6,430,000, respectively. Net present values of two plants at various discount factors have been determined and the IRR have been estimated as 13.0 and 20.1% for the stand-alone plant and integrated plant, respectively. Sensitivity analysis reveals that the cash flow of the project would be increased or decreased up to 40, 65 and 120% by varying production factors of cost of chemical activation agent, production capacity and selling price of activated carbon, respectively, in the extent of ±25%. [Copyright &y& Elsevier]

The adsorption of three acid dyes onto activated carbon has been studied. Three single, three binary and one ternary systems have been investigated and both equilibrium and kinetic studies have been determined. The equilibrium capacities based on the Langmuir analysis are 0.253, 0.125 and 0.219 mmol g-1 carbon for Acid Blue 80, Acid Red 114 and Acid Yellow 117, respectively. The batch adsorber rate data for the seven systems have been analysed based on an intraparticle diffusion rate parameter derived from the plots of dye adsorbed versus the square root of time. The data indicate the adsorption mechanism is predominantly intraparticle diffusion. The multicomponent system rate parameters have been correlated with the single component rate parameters by the use of the Langmuir equilibrium parameters. [Copyright &y& Elsevier]

Novel fixed-bed adsorption investigations applying carbon nanotube (CNT) coated poly-amidoamine dendrimer (PAMAM) as an adsorbent have been studied for the adsorption of As(III) as arsenous acid, Co 2+ , and Zn 2+ from aqueous solution. FTIR, SEM, 1 H NMR, TGA, TEM, Raman Spectra and zeta potential measurements have been employed for characterizing the synthetic nanocomposite and these techniques indicated that the dendrimer functionalized CNTs have been favorably synthesized. The effects of process parameters including flow rate, initial concentration and bed height on the duration of the breakthrough time, mass transfer zone, adsorption capacity and exhaustion time at breakthrough were investigated. Decreasing initial concentration and flow rate, and increasing bed height, increased the exhaustion and breakthrough times. In addition, the removal capacity at breakthrough was enhanced with decreasing flow rate, initial ion concentration and increasing bed height. The notably high maximum adsorption capacities at fixed bed breakthrough of the studied ions were 432 mg/g for As(III) as arsenous acid, 494 mg/g for Co 2+ , and 470 mg/g for Zn 2+ at bed height of 12.0 cm, influent concentration of 100 mg/L and flow rate of 0.5 mL/min. Almost no previous fixed bed data for PAMAMS exist. Adsorption results were correlated using the Thomas, Yoon-Nelson, and Bohart-Adams models. Empirical breakthrough curves were found to be best fitted with the predicted curves produced by the Thomas and Yoon-Nelson equations. This study illustrates the efficiency of PAMAM/CNT nanocomposite for the adsorption of As(III), Co 2+ , and Zn 2+ from aqueous solution. [ABSTRACT FROM AUTHOR]

In the present study, hydroxyiron-modified montmorillonite (HyFe-MMT) nanoclay was prepared using a simple wet chemical synthesis method. Arsenite (As (III)) removal using raw montmorillonite and HyFe-MMT was compared and evaluated by adsorption experiments conducted under various conditions (adsorbent dosage, iron loading, contact time, pH, and initial As (III) concentration). The nanoclays were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectrometry (FTIR), BET surface area analysis, thermogravimetric analysis, scanning electron (SEM) microscopy, and transmission electron microscopy (TEM). Fast adsorption kinetics were observed in which more than 55% of As (III) was removed using HyFe-MMT within the first 30 s of the adsorption process. The kinetics were most accurately modeled using the pseudo-second-order equation (R 2  = 1). Optimum As (III) adsorption was obtained between a pH of 6 to 7. The Freundlich model properly described the adsorption process (R 2  > 0.99). It was determined that the adsorption capacity of raw MMT was increased to more than five times after iron modification. The HyFe-MMT adsorbent presented could be used for arsenic contaminated groundwater, drinking water, or wastewater. [ABSTRACT FROM AUTHOR]

Sludge, a byproduct produced from numerous industrial activities, has been recognized as an ecological burden for the society. However, viewing the sludge, as a carbon-rich material, has stimulated new gateways for the production of porous activated carbons for water treatment applications. Herein, various textural properties of the sludge-based activated carbons have been compiled and critically reviewed with the focus on surface area, pore size and pore size distribution for both physically and chemically activated carbons. It has been found that chemical activation using various activating agents yields more superior adsorbents with high specific surface areas than physical activation methods. Moreover, the potential of sludge-derived activated carbons for the sequestration of metals and dyes from aqueous media has been discussed. Furthermore, the adsorption mechanism in several adsorbent–adsorbate systems and the effect of various parameters on the adsorption behavior of different dyes and metals on sludge-based activated carbons have been reviewed. It has been shown that the pollutant uptake capacities of the adsorbents derived from sewage sludge are not only governed by the textural properties of the adsorbents, but also by their surface properties, such as the functional groups and the surface charge and thus it is proposed that both of these crucial factors be considered concurrently. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the recovery of base oils from waste lubricants was investigated using a novel combination of solvent extraction and adsorption on solids. The performance of six extracting solvents (n-hexane, 1-butanol, petroleum ether, 1-hexanol, carbon tetra chloride, and acetone) was evaluated experimentally. Solvent to oil ratios from 1:1 to 4:1 were also examined. This research has studied the effect of the use of KOH to enhance flocculation. The results show that 1-butanol achieved the best performance with the maximum percent sludge removal, followed by n-hexane, petroleum ether, 1-hexanol, carbon tetrachloride, and acetone. The percentage of oil sludge was found to increase with the increase of solvent to oil ratio until it reached the maximum at the ratio of 3:1. The application of an adsorption process using different adsorbent materials was investigated. Adsorbent materials such as almond shell, walnut shell, eggshell, and acid activated clay which were prepared locally were used. It was found that the acid activated clay was able to give the best conditions for treating the waste oil followed by the almond shell powder. The results from the test showed that, viscosity increased from 38.3cst for used lube oil to 85cst for acid/clay treatment and the flash point increase from 178°C to 238°C, while the density decreased from 912 to 896kg/m3, the pour point from −6 to −13.2°C and colour from 0.53 to 0.12. Other results from the different tests showed varying degrees of improvement with the best results obtained using the acid/clay treatment. [Copyright &y& Elsevier]

Abstract: Novel Fe loaded activated carbons have been prepared from sugar beet pulp (BP) agricultural residues by direct steam activation followed by iron impregnation with or without previous oxidation. The corresponding activated carbons were: BP–H2O, BP–H2O–Fe, BP–H2O–H2O2–Fe and BP–H2O–MnO2–Fe. The textural characterization of these tailored activated carbons was based on nitrogen adsorption/desorption isotherms leading to BET surface area values between 741 and 821m2/g and total porous volumes between 0.58 and 0.79cm3/g. Elemental analysis and ash content showed that carbon content reached 78% for BP–H2O with 13.6% of ash and decreased to 50% in iron-based materials. BP–H2O and BP–H2O–Fe revealed a basic nature with pHPZC values of 9.8 and 9 respectively while BP–H2O–H2O2–Fe and BP–H2O–MnO2–Fe had acid pHPZC (5.1 and 3.6). Their surface chemistry has been investigated by XPS analysis and by the quantification of the surface chemical moieties based on Boehm’s approach. A clear relationship was found between the surface iron content and the strong acidic groups. Arsenic (As(V)) adsorption isotherms were performed and Langmuir, Freundlich, Redlich–Peterson models were used to describe the experimental data by non-linear regression. It was found that Redlich–Peterson isotherm provided the best fit and the Langmuir adsorption capacities confirmed that the iron-based activated carbons were highly attractive for As(V) removal with capacities up to 17mgg−1. Finally, it has been shown that the surface iron content determined by XPS analysis is very well correlated with Langmuir qm values (r 2 =0.982) and with the strong acidic moieties deduced from the Boehm’s method. [Copyright &y& Elsevier]

Abstract: Selective gold adsorption was investigated for the NH2-MCM-41 and SH-MCM-41 adsorbents prepared by grafting aminopropyl and thiolpropyl groups on the surface of the MCM-41 mesoporous silica. The single component adsorption of gold, copper and nickel from salt solutions, and the binary adsorption studies of Au3+/Cu2+ and Au3+/Ni2+ solutions were carried out for the two adsorbents. Gold adsorption from simulated gold mining solution and gold electroplating wastewater were also reported. The NH2-MCM-41 and SH-MCM-41 displayed strong affinity for gold in the solution and both exhibited 100% selectivity for the gold in the binary Au3+/Cu2+ and Au3+/Ni2+ solutions. The NH2-MCM-41 is more suitable for the gold mining solution, while SH-MCM-41 is efficient for gold adsorption from the electroplating waste containing high amount of organics. The gold was recovered as high purity salt solution by elution with mineral acid for NH2-MCM-41 and thiolsulfate for SH-MCM-41. The regenerated adsorbent remained selective to gold and exhibited the same adsorption capacity as the fresh adsorbent. Also, the regenerated adsorbent performed well even after several reuses. [Copyright &y& Elsevier]