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This study investigates the adsorptive removal of malachite green (MG) dye from aqueous solutions using chemically modified lime-peel-based activated carbon (LPAC). The adsorbent prepared was characterized using FTIR, SEM, Proximate analysis and BET techniques, respectively. Central composite design (CCD) in response surface methodology (RSM) was used to optimize the adsorption process. The effects of three variables: activation temperature, activation time and chemical impregnation ratio (IR) using KOH and their effects on percentage of dye removal and LPAC yield were investigated. Based on CCD design, quadratic models and two factor interactions (2FI) were developed correlating the adsorption variables to the two responses. Analysis of variance (ANOVA) was used to judge the adequacy of the model. The optimum conditions of MG dye removal using LPAC are: activation temperature (796°C), activation time (1.0 h) and impregnation ratio (2.6), respectively. The percentage of MG dye removal obtained was 94.68 % resulting in 17.88 % LPAC yield. The percentage of error between predicted and experimental results for the removal of MG dye is 0.4 %. Model prediction was in good agreement with experimental results and LPAC was found to be effective in removing MG dye from aqueous solution.

Continuous production of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD) method was investigated in a rotary reactor. The aim of the study was to investigate the effect of catalyst feeding rate and reaction time on the MWCNTs production yield and purity. Bimetallic Co-Mo supported on MgO was used for the growth of MWCNTs and methane gas was used as the carbon precursor. The results indicated that the highest yield of MWCNTs production was attained at the reaction time of 180 min and catalyst feeding rate of 100 mg/min; this sample also had the highest purity (99.16%). SEM and TEM analyses of the synthesized product confirmed that most of the MWCNTs were sinuous and entangled with a uniform diameter. Raman spectroscopy indicated that the as-produced MWCNTs were mostly graphitic with few disordered carbon and impurities. The results highlighted that synthesized MWCNTs were highly pure which eliminates the need for MWCNTs purification process.

In this paper, screening study in regards to preparation of functionalized multi-walled carbon nanotubes (FMWNT)supported bi-metallic catalyst is discussed. Functional groups such as hydroxyl and carboxylic acid are introduced on multi-walled carbon nanotubes (MWCNT) surface using acid treatment method with the aid of probe-type ultrasonication. It is done by varying the concentration of nitric acid (HNO 3) and sulphuric acid (H 2 SO 4), acid volume ratio and treatment duration. Catalysts with different ratios of cerium and nickel nanoparticles which are either loaded inside or outside of MWCNT were prepared via ultrasonic-assisted co-precipitation method (NiCe/CNT). This is done to study the effect of cerium loadings. The characterization of the FMWNT and catalysts are carried out using transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and Raman spectroscopy. The results showed that the treatment in concentrated HNO 3 /H 2 SO 4 with volume ratio of 3:1 for 8 h was the most suitable condition to generate large amount of surface oxygen group with minimal defects. The observations for each used condition were discussed thoroughly. Decoration of MWCNT with different metal loadings resulted in different distribution and dispersion of metal on nanotubes surface.

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