Mohammad N.M. Ahmad

Effect of carbon surface chemistry on the removal of reactive dyes from textile effluent

Abstract The removal efficiency of activated carbon Filtrasorb 400 (F-400) towards three highly used reactive dyes in the textile industry was investigated. In this work, the adsorption capacities for the anionic reactive dyes, namely; Remazol Reactive Yellow, Remazol Reactive Black and Remazol Reactive Red were determined. The adsorption capacity data showed a high removal ability for the three reactive dyes and a distinguished ability for R. Yellow. The high adsorption capacities for F-400 were attributed to the net positive surface charge during the adsorption process. Surface acidity, surface basicity, H + and OH − adsorption capacities and pH ZPC for F-400 were estimated and compared with other reported values.

Adsorption behaviour of methylene blue onto Jordanian diatomite: A kinetic study

The effect of initial concentration, particle size, mass of the adsorbent, pH and agitation speed on adsorption behaviour of methylene blue (MB) onto Jordanian diatomite has been investigated. The maximum adsorption capacity, q, increased from 75 to 105 mg/g when pH of the dye solution increased from 4 to 11. It is clear that the ionisable charge sites on the diatomite surface increased when pH increased from 4 to 11. When the solution pH was above the pH(ZPC), the diatomite surface had a negative charge, while at low pH (pH<5.4) it has a positive charge. The adsorption capacity increased from 88.6 to 143.3mg/g as the initial MB concentrations increased from 89.6 to 225.2mg/dm(3). The experimental results were also applied to the pseudo-first and -second order kinetic models. It is noticed that the whole experimental data of MB adsorption onto diatomite did not follow the pseudo-first order model and had low correlation coefficients (R(2)<0.3). The calculated adsorption capacity, q(e,cal), values obtained from pseudo-first order kinetic model did not give acceptable values, q(e,exp.) The maximum uptake capacity seems to be independent of the particle size of the diatomite when the particle size distribution is less than 250-500 microm. While at larger particle size 250-500 microm, the maximum uptake capacity was dependent on the particle size. It would imply that the MB adsorption is limited by the external surface and that intraparticle diffusion is reduced. The effect of the agitation speeds on the removal of MB from aqueous solution using the diatomite is quite low. The MB removal increased from 43 to 100% when mass of the diatomite increased from 0.3 to 1.7 g.

Adsorption characteristics of reactive dyes in columns of activated carbon

Adsorption behaviour of reactive dyes in fixed-bed adsorber was evaluated in this work. The characteristics of mass transfer zone (MTZ), where adsorption in column occurs, were affected by carbon bed depth and influent dye concentration. The working lifetime (t(x)) of MTZ, the height of mass transfer zone (HMTZ), the rate of mass transfer zone (RMTZ), and the column capacity at exhaustion (q(column)) were estimated for the removal of remazol reactive yellow and remazol reactive black by carbon adsorber. The results showed that column capacity calculated at 90% of column exhaustion was lower than carbon capacity obtained from equilibrium studies. This indicated that the capacity of activated carbon was not fully utilized in the fixed-bed adsorber. The bed-depth service time model (BDST) was applied for analysis of reactive yellow adsorption in the column. The adsorption capacity of reactive yellow calculated at 50% breakthrough point (N(0)) was found to be 0.1 kg kg(-1) and this value is equivalent to about 14% of the available carbon capacity. The results of this study indicated the applicability of fixed-bed adsorber for removing remazol reactive yellow from solution.

Adsorption mechanisms of removing heavy metals and dyes from aqueous solution using date pits solid adsorbent

A potential usefulness of raw date pits as an inexpensive solid adsorbent for methylene blue (MB), copper ion (Cu(2+)), and cadmium ion (Cd(2+)) has been demonstrated in this work. This work was conducted to provide fundamental information from the study of equilibrium adsorption isotherms and to investigate the adsorption mechanisms in the adsorption of MB, Cu(2+), and Cd(2+) onto raw date pits. The fit of two models, namely Langmuir and Freundlich models, to experimental data obtained from the adsorption isotherms was checked. The adsorption capacities of the raw date pits towards MB and both Cu(2+) and Cd(2+) ions obtained from Langmuir and Freundlich models were found to be 277.8, 35.9, and 39.5 mg g(-1), respectively. Surface functional groups on the raw date pits surface substantially influence the adsorption characteristics of MB, Cu(2+), and Cd(2+) onto the raw date pits. The Fourier transform infrared spectroscopy (FTIR) studies show clear differences in both absorbances and shapes of the bands and in their locations before and after solute adsorption. Two mechanisms were observed for MB adsorption, hydrogen bonding and electrostatic attraction, while other mechanisms were observed for Cu(2+) and Cd(2+). For Cu(2+), binding two cellulose/lignin units together is the predominant mechanism. For Cd(2+), the predominant mechanism is by binding itself using two hydroxyl groups in the cellulose/lignin unit.

Influence of solution chemistry on Cr(VI) reduction and complexation onto date-pits/tea-waste biomaterials.

Tea waste (TW) and Date pits (DP) were investigated for their potential to remove toxic Cr(VI) ions from aqueous solution. Investigations showed that the majority of the bound Cr(VI) ions were reduced to Cr(III) after biosorption at acidic conditions. The electrons for the reduction of Cr(VI) may have been donated from the TW and DP biomasses. The experimental data obtained for Cr(VI)-TW and Cr(VI)-DP at different solution temperatures indicate a multilayer type biosorption, which explains why the Sips isotherm accurately represents the experimental data obtained in this study. The Sips maximum biosorption capacities of Cr(VI) onto TW and DP were 5.768 and 3.199 mmol/g at 333 K, respectively, which is comparatively superior to most other low-cost biomaterials. Fourier transform infrared spectroscopic analysis of the metal loaded biosorbents confirmed the participation of -COOH, -NH(2) and O-CH(3) groups in the reduction and complexation of chromium. Thermodynamic parameters demonstrated that the biosorption of Cr(VI) onto TW and DP biomass was endothermic, spontaneous and feasible at 303-333 K. The results evidently indicated that tea waste and date pits would be suitable biosorbents for Cr(VI) in wastewater under specific conditions.

Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite

The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as delta-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the d-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern.

Modelling and Fixed Bed Column Adsorption of Cr(VI) onto Orthophosphoric Acid-activated Lignin

Abstract The advantage of using an available and abundant residual biomass, such as lignin, as a raw material for activated carbons is that it provides additional economical interest to the technical studies. In the current investigation, a more complete understanding of adsorption of Cr(VI) from aqueous systems onto H3PO4-acid activated lignin has been achieved via microcolumns, which were operated under various process conditions. The practice of using microcolumn is appropriate for defining the adsorption parameters and for screening a large number of potential adsorbents. The effects of solution pH (2–8), initial metal ion concentration (0.483–1.981 mmol·L−1), flow rate (1.0–3.1 cm3·min−1), ionic strength (0.01–0.30 mmol·L−1) and adsorbent mass (0.11–0.465 g) on Cr(VI) adsorption were studied by assessing the microcolumn breakthrough curve. The microcolumn data were fitted by the Thomas model, the modified Dose model and the BDST model. As expected, the adsorption capacity increased with initial Cr(VI) concentration. High linear flow rates, pH values and ionic strength led to early breakthrough of Cr(VI). The model constants obtained in this study can be used for the design of pilot scale adsorption process.

Biosorption Characteristics of Sawdust for the Removal of Cd(ii) Ions: Mechanism and Thermodynamic Studies

Surface reaction methodology was employed for the optimization of cadmium removal onto sawdust with respect to various physico-chemical parameters. FT-IR was principally employed for the assessment of the chemical structure of sawdust. The biosorption equilibrium data were best represented by Khan and Langmuir isotherms. The monolayer sorption capacity obtained from Langmuir model was found to be 41.21 mg/g. Biosorption showed pseudo second order rate kinetics at different initial concentration of Cd(II). The intraparticle diffusion study indicated that film diffusion may be involved in the current study. Thermodynamic parameters showed that the sorption process is exothermic and non-spontaneous.

Dilute phosphoric acid-catalysed hydrolysis of municipal bio-waste wood shavings using autoclave parr reactor system.

The visibility of using municipal bio-waste, wood shavings, as a potential feedstock for ethanol production was investigated. Dilute acid hydrolysis of wood shavings with H₃PO₄ was undertaken in autoclave parr reactor. A combined severity factor (CSF) was used to integrate the effects of hydrolysis times, temperature and acid concentration into a single variable. Xylose concentration reached a maximum value of 17 g/100 g dry mass corresponding to a yield of 100% at the best identified conditions of 2.5 wt.% H₃PO₄, 175 °C and 10 min reaction time corresponding to a CSF of 1.9. However, for glucose, an average yield of 30% was obtained at 5 wt.% H₃PO₄, 200 °C and 10 min. Xylose production increased with increasing temperature and acid concentration, but its transformation to the degradation product furfural was also catalysed by those factors. The maximum furfural formed was 3 g/100 g dry mass, corresponding to the 24% yield.

Compression testing of granular NPK fertilizers

The crush strength of granular NPK fertilizer has been accurately determined using Instron compression testing equipment. Stress-strain analysis shows a distinctive break point followed by break up of granule fragments. The force required to crush the granules is a function of the granule diameter but the calculated pressure required to crush each granule remained relatively constant. Factors such as moisture ingress and coating oils have been shown to affect granule strength. A direct link between caking of granular fertilizers and crush strength has been established.