Geopolymer is synthesized by polycondensation of SiO4 and AlO4 aluminosilicate complexes, tetrahedral frames linked with shared sialate oxygen. This paper studies the effect of the solids-to-fluids (S/L) and Na2SiO3/NaOH proportions on the preparing of metakaolin inorganic membrane geopolymer. By consolidating a mixture of metakaolin with sodium hydroxide, sodium silicate and foaming agent, the geopolymer membrane was made in required shape about 1 cm and cured at 80°C for 24 hours. After the curing process, the properties of the samples were tested on days 7. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution were utilized as an alkaline activator with a NaOH fixation fixed at 10 M. The geopolymer inorganic membrane tests were set up with various S/L proportions (0.8, 1.0, 1.2 and 1.4) and Na2SiO3/NaOH proportions (0.5, 1.0, 1.5, 2.0 and 2.5). Aluminium (Al) powder as a foaming agent was used to create bubbles in porous structure and provide details on the development of membrane geopolymers. This metakaolin membrane, based on the geopolymer, was synthesized by a suspension that depends on the fast cementing mechanism of high-temperature slurries. Porous geopolymeric circles provided a homogeneous composition and quantitative distribution of pores. The water absorption, density, impact toughness testing and microstructure analyses were studied. However, considering the promising results, an adjustment in the mix design of the metakaolin inorganic membrane geopolymer mixtures could increase their mechanical properties without negatively affecting the mechanical properties and porosity, making these sustainable materials a suitable alternative to traditional porous cement concrete.

For ages, concrete has been used to construct underwater structures. Concrete laying underwater is a very complex procedure important to the success or failure of underwater projects. This paper elucidates the influence of alkali activator ratios on geopolymers for underwater concreting; focusing on the geopolymer concrete synthesized from fly ash and kaolin activated using sodium hydroxide and sodium silicate solutions. The geopolymer mixtures were designed to incorporate multiple alkali activator ratios to evaluate their effects on the resulting geopolymers’ properties. The fresh concrete was molded into 50 mm cubes in seawater using the tremie method and tested for its engineering properties at 7 and 28 days (curing). The control geopolymer and underwater geopolymers’ mechanical properties, such as compressive strength, water absorption density, and setting time were also determined. The differences between the control geopolymer and underwater geopolymer were determined using phase analysis and functional group analysis. The results show that the geopolymer samples were optimally strengthened at a 2.5 alkali activator ratio, and the mechanical properties of the control geopolymer exceeded that of the underwater geopolymer. However, the underwater geopolymer was determined to be suitable for use as underwater concreting material as it retains 70% strength of the control geopolymer.

The present study is aimed to access the growth rates, biomass productivity and nutrient removal in different concentrations of microalgae Botryococcus sp. beads using kitchen wastewater as a media. Verhulst logistic kinetic model was used to measure the optimal concentrations of microalgae Botryococcus sp. in kitchen wastewater in terms of cell growth rate kinetics and biomass productivity. The study verified that the maximum productivity was recorded with 1×106 cell/ml of the initial concentration of Botryococcus sp. with 42.64 mg/l/day and the highest removal of tp and ammonia was obtained (78.14% and 60.53% respectively). The highest specific growth rate of biomass at 0.2896 μmax/d compare to other concentrations, while the lowest occurred at concentrations of 105 cells/ml at 0.0412 μmax/d. The present study shows the different concentrations of Botryococcus sp. in alginate beads culturing in kitchen wastewater influence the cells growth of biomass and nutrient uptake with optimum concentration (106 cells/ml) of Botryococcus sp. which is suggested for wastewater treatment purposes. The result of scanning electron microscopy (sem) shows differences in morphology in terms of surface; smoother and cleaner (before the experiment), cracks and rough surface with black/white spots (after the experiment). These findings seemly can be applied efficiently in kitchen wastewater treatment as well as a production medium for microalgae biomass.