Md. Azharul Islam

Photocatalytic degradation using design of experiments: A review and example of the Congo red degradation

The use of chemometric methods such as response surface methodology (RSM) based on statistical design of experiments (DOEs) is becoming increasingly widespread in several sciences such as analytical chemistry, engineering and environmental chemistry. Applied catalysis, is certainly not the exception. It is clear that photocatalytic processes mated with chemometric experimental design play a crucial role in the ability of reaching the optimum of the catalytic reactions. The present article reviews the major applications of RSM in modern experimental design combined with photocatalytic degradation processes. Moreover, the theoretical principles and designs that enable to obtain a polynomial regression equation, which expresses the influence of process parameters on the response are thoroughly discussed. An original experimental work, the photocatalytic degradation of the dye Congo red (CR) using TiO(2) suspensions and H(2)O(2), in natural surface water (river water) is comprehensively described as a case study, in order to provide sufficient guidelines to deal with this subject, in a rational and integrated way.

Preparation of activated carbons from agricultural residues for pesticide adsorption.

Activated carbons (ACs) can be used not only for liquid but also for vapour phase applications, such as water treatment, deodorisation, gas purification and air treatment. In the present study, activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) from water. For the characterization of the activated carbons ICP, SEM, FTIR and XRD analyses were performed. Adsorption kinetics and equilibrium isotherms were investigated for all biomass activated carbons in aqueous solutions. Experimental data of BP adsorption have fitted best to the pseudo 2nd-order kinetic model and Langmuir isotherm. The study resulted that corn cobs showed better adsorption capacity than the other biomass ACs. Comparison among ACs from biomass and commercial ones (F400 and Norit GL50) revealed that the first can be equally effective for the removal of BP from water with the latter.

Mesoporous activated carbon prepared from NaOH activation of rattan (Lacosperma secundiflorum) hydrochar for methylene blue removal

Hydrothermal carbonization of biomass wastes presents a promising step in the production of cost-effective activated carbon. In the present work, mesoporous activated carbon (HAC) was prepared by the hydrothermal carbonization of rattan furniture wastes followed by NaOH activation. The textural and morphological characteristics, along with adsorption performance of prepared HAC toward methylene blue (MB) dye, were evaluated. The effects of common adsorption variables on performance resulted in a removal efficiency of 96% for the MB sample at initial concentration of 25mg/L, solution pH of 7, 30°C, and 8h. The Langmuir equation showed the best isotherm data correlation, with a maximum uptake of 359mg/g. The adsorbed amount versus time data was well fitted by a pseudo-second order kinetic model. The prepared HAC with a high surface area of 1135m2/g and an average pore size distribution of 35.5Å could be an efficient adsorbent for treatment of synthetic dyes in wastewaters.

Pyrolysis kinetics of raw and hydrothermally carbonized Karanj (Pongamia pinnata) fruit hulls via thermogravimetric analysis

The pyrolysis of karanj fruit hulls (KFH) and karanj fruit hull hydrothermal carbonization (KFH-HTC) hydrochar was thermogravimetrically investigated under a nitrogen environment at 5 °C/min, 10 °C/min, and 20 °C/min. The pyrolysis decomposition of KFH biomass was faster than that of KFH-HTC hydrochar because of the high volatility and fixed carbon of KFH biomass. Weight loss percentage was also affected by the heating rates. The kinetic data were evaluated with the Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods. The activation energy values obtained with these two methods were 61.06 and 68.53 kJ/mol for KFH biomass and 130.49 and 135.87 kJ/mol for KFH-HTC hydrochar, respectively. The analysis of kinetic process mechanisms was verified with the Coats-Redfern method. KFH-HTC hydrochar may play a potential role in transforming biomass to energy-rich feedstock for thermochemical applications because of its high heating value, high fixed carbon, and low ash and sulfur contents.

A thermogravimetric analysis of the combustion kinetics of karanja (Pongamia pinnata) fruit hulls char.

The combustion characteristics of Karanj fruit hulls char (KFH-char) was investigated with thermogravimetry analysis (TGA). The TGA outlined the char combustion thermographs at a different heating rate and isoconversional methods expressed the combustion kinetics. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods authenticated the char average activation energy at 62.13 and 68.53kJ/mol respectively, enough to derive the char to burnout. However, the Coats-Redfern method verified the char combustion via complex multi-step mechanism; the second stage mechanism has 135kJ/mol average activation energy. The TGA thermographs and kinetic parameters revealed the adequacy of the KFH-char as fuel substrate than its precursor, Karanj fruit hulls (KFH).

Combustion kinetics of hydrochar produced from hydrothermal carbonisation of Karanj (Pongamia pinnata) fruit hulls via thermogravimetric analysis.

This study examined the combustion profile and kinetics of hydrochar produced from hydrothermal carbonisation (HTC) of Karanj fruit hulls (KFH). The HTC-KFH hydrochar combustion kinetics was investigated at 5, 10, and 20°C/min by thermogravimetric analysis. The kinetics model, Kissinger-Akahira-Sunose revealed the combustion kinetics parameters for the extent of conversion from 0.1 to 0.8; the activation energy varies from 114 to 67 kJ/mol respectively. The hydrochar combustion followed multi-steps kinetics; the Coats-Redfern models predicted the activation energies and pre-exponential constants for the hydrochar combustion zones. The diffusion models are the effective mechanism in the second and third zone.

Human hair-derived high surface area porous carbon material for the adsorption isotherm and kinetics of tetracycline antibiotics

In this work, a human hair-derived high surface area porous carbon material (HHC) was prepared using potassium hydroxide activation. The morphology and textural properties of the HHC structure, along with its adsorption performance for tetracycline (TC) antibiotics, were evaluated. HHC showed a high surface area of 1505.11m2/g and 68.34% microporosity. The effects of most important variables, such as initial concentration (25-355mg/L), solution pH (3-13), and temperatures (30-50°C), on the HHC adsorption performance were investigated. Isotherm data analysis revealed the favorable application of the Langmuir model, with maximum TC uptakes of 128.52, 162.62, and 210.18mg/g at 30, 40, and 50°C, respectively. The experimental data of TC uptakes versus time were analyzed efficiently using a pseudo-first order model. Porous HHC could be an efficient adsorbent for eliminating antibiotic pollutants in wastewater.

Adsorption of direct yellow 27 from water by poorly crystalline hydroxyapatite prepared via precipitation method

Abstract In the present study, hydroxyapatite powders were prepared by modified precipitation method and characterized by XRD, FT-IR and N2 adsorption–desorption techniques. The prepared nonporous particles were organized to agglomerate with mesoporous structure and consisted of low crystallinity Ca-deficient hydroxyapatite and in amorphous phase. The commercial direct yellow 27 was selected as a model dye in order to examine the adsorption capacity of hydroxyapatite at room temperature. The adsorption isotherms are transformed from L-type to S-type curve, in Giles classification, by increasing the pH values. Equilibrium data fitted very well to the Langmuir model, signifying the energetic homogeneity of hydroxyapatite surface adsorption sites. The dye sorption kinetics was fairly described by the pseudo-first-order kinetic model.

Statistical optimisation by combination of response surface methodology and desirability function for removal of azo dye from aqueous solution

Traditional one by one factor analysis has some drawbacks related to time, cost, feasibility and optimisation. To overcome of these process parameters, response surface methodology (RSM) with Central Composite Design (CCD) was used in this study to evaluate the effects of main factors and their interaction for congo red (CR) removal and to derive the model optimisation by composition of all parameters in order to reduce excessive experiments. The ‘profiling and desirability function’ was also employed for the specific values of controlled parameters for optimisation and highest desirability. The use of analysis of variance (ANOVA) and ‘t’ test showed that the interactions of all studied parameters (pH, dose and concentration) on congo red (CR) dye for adsorbent (used tea leaves) have significant impact of removal %. The lack of fit test (LOF) and residual analysis were also performed for adequacy of the model. Applying desirability function, the optimal conditions of pH, adsorbent dose and initial concentration were found to be 4.32, 0.47 g, and 92.05 mg L−1 corresponding to 93.46% removal for used tea leaves. Batch equilibration method was followed for the removal of CR dye for adsorbent. Langmuir adsorption isotherm was conformed well to removal data for used tea leaves.

Cross-linked chitosan thin film coated onto glass plate as an effective adsorbent for adsorption of reactive orange 16

Fabrication of an immobilized cross-linked chitosan-epichlorohydrine thin film (CLCETF) onto glass plate for adsorption of reactive orange 16 (RO16) dye was successfully studied using the direct casting technique. Adsorption experiments were performed as a function of contact time, initial dye concentration (25mg/L to 350mg/L), and pH (3-11). The adsorption isotherm followed the Langmuir model. The adsorption capacity of CLECTF for RO16 was 356.50mg/g at 27±2°C. The kinetics closely followed the pseudo-second-order model. Results supported the potential use of an immobilized CLECTF as effective adsorbent for the treatment of reactive dye without using filtration process.