No abstract

This study presents findings from experiments on the preparation and characterization of locally available fly ash, quicklime and the CaO/fly ash sorbent, synthesized using the atmospheric hydration process. The CaO was obtained from calcination of limestone in a laboratory kiln at a temperature of 900°C. The sorbents were prepared under different hydration conditions: CaO/fly ash weight ratio (1∶1 to 1∶3), hydration temperature (55°C-75ºC) and hydration period (4-8 h). Results show that the specific surface area of CaO/ fly ash sorbents (8.8-23.6 m 2 /g) was higher than that of the CaO (4.78 m 2 /g) at all preparation conditions. The SEM micrographs show that the prepared sorbent had a more porous structure than either the fly ash or the CaO. The X-ray diffraction (XRD) analysis shows the presence of complex compounds containing calcium silicate hydrate in the synthesized sorbents. This contributed to the high BET specific surface area. The Brunauer-Emmett-Teller (BET) specific surface area was found to decrease with increase in the amount of fly ash with the ratio of 1∶1 (CaO/Fly ash) giving the highest value. It was also found that an increase in the hydration time resulted in an increased BET specific surface area, although there was only a slight effect on the same by an increase in temperature.

The aim of this study was to explore the use of adsorption in the removal of synthetic dyes in water bodies. These dyes pose a serious threat to both aquatic and human lives because of their toxicity and persistence in the environment. There is therefore an urgent need to remove them from water before discharge to the environment. Many of the current dye treatment methods are generally inefficient and expensive; however, adsorption is the most preferred method due to its inherent benefits such as simplicity, ease of operation, low cost and insensitivity to toxic environments. The study evaluated the removal of Multi-Active-Blue (MAB) dye from aqueous solution using polypyrrole-magnetitenano-composite (PPy/Fe 3 O 4 ) adsorbent in a fixed-bed adsorption column. The influences of initial MAB dye concentration, bed mass and flow rate at the influent stream on the adsorption performance were investigated in an up-flow fashion. Results showed that early breakthrough time (t b ) was attained at high solution flow rates and dye concentrations and low bed mass. Increasing concentration from 50 to 150mg/L resulted in a decrease in ‫ݐ‬ from 610 to 110 min. Furthermore, at the studied conditions, the highest breakthrough time obtained was 690 min at which 228 bed volumes were processed at 1.45g/L Adsorbent Exhaustion Rate (AER).The adsorber design parameters were calculated by fitting the experimental data to the column adsorption models and based on analysis of linear regression coefficients (R 2 ), it was established that the MAB dye adsorption was described best by Yoon-Nelson model throughout the entire breakthrough profile, while Bohart-Adams model fitted only the initial portion of the profiles. Accordingly, it was concluded that PPy-Fe 3 O 4 nano-composite material is a promising adsorbent for cleaning textile dye polluted water.