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CONCLUSIONS AND RECOMMENDATIONS
This section focuses on the conclusions that are drawn from the results of the experimental runs for hydrothermal synthesis of zeolite A and electrodialysis (ED) desalination system using cement mortar-structured zeolite membranes from corn (Zea Mays) stover ash.
6.1 Conclusions of the Study
Zeolite A has been effectively synthesized using corn stover ash as the raw material, and this agricultural waste represents an alternate method for reducing environmental waste impact. From the findings of the one-factor at a time test in synthesizing zeolite A from corn stover ash, the highest % yield (71.74%) was achieved at calcination temperature of 500oC, fusion ratio of 1.0:1.5, and 9-hour curing time. The CEC performance also indicated that the 1.0:1.5 fusion ratio is the most advantageous proportion among the various fusion ratios, while the 9-hour curing period produces the most advantageous outcome, with a CEC of 2.439 meq Na+/g of synthesized anhydrous zeolite A in hydrogen form (zeolite HA). The CEC performance of all the varied fusion ratios of corn stover ash: NaOH at various curing times was found to be superior to that of commercial zeolite A (1.641 meq Na+/g). Response Surface Methodology (RSM) with Central Composite Design in multiple objective optimizations with desirability function was used to study the effects of several parameters on hydrothermal synthesis optimization, including calcination temperature, fusion ratios, and curing time. The relationship between operational parameters and the responses is mathematically described. According to the ANOVA results, the calcination temperature, fusion ratio,
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the interaction between the calcination temperature and fusion ratios, and the squared of the calcination temperature, fusion ratios, and curing time are the relevant factors in the mathematical model of the percent yield. On the other hand, fusion ratios, curing time, and the square of the calcination temperature, as well as fusion ratios, are significant variables in the CEC's mathematical model. The obtained optimum conditions for the maximum % yield (75.08%) and CEC (2.282 meq/g) were as follows: calcination temperature (534.5oC), fusion ratios (1:1.708), and curing time (10.50 hours). The maximum overall desirability of 0.597 was attained.
In one-factor at a time test for ED desalination system using cement mortar- structured zeolite membrane (CMSZ), highest removal of sodium (Na+) ion (74%) was obtained at 15V and CMSZ membrane with a binder ratio of 85:15. The sodium ion removal for all the varied binder ratios at various applied voltage was found to be superior compared to that of commercial zeolite A employed in CMSZ. The optimization of ED desalination system revealed that utilizing synthetic zeolite A in hydrogen form from corn stover ash into CMSZ membrane is effective in removing sodium ions from the prepared salt solution, yielding an 80.68 percent removal efficiency. All of the variables examined, specifically the binder ratio, the applied voltage, and the number of stacked cell pairs, were found to have an influence on sodium ion reduction. According to the quadratic response surface model, the ideal settings examined are in the intermediate ranges with the biggest percentage reduction.
In general, an ED desalination system using CMSZ membranes proved to be an efficient alternative way for treating saltwater or brackish water to produce fresh water in the end.
6.2 Recommendations for the Study
The efficiency of the ED desalination system utilizing CMSZ membrane from the hydrothermal synthesis of zeolite A using corn stover ash has been validated by
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experimental results. To fully appreciate the usefulness of the ED desalination system in seawater or brackish water treatment using natural ion-exchanging materials such as zeolite A from corn (Zea Mays) stover ash, the following should be examined in future related studies:
On the hydrothermal synthesis:
1. The impact of operational variables such as aging temperature and time, curing temperature, and drying temperature and time should be investigated.
2. Research on the use of synthesized zeolite A as ion exchangers and adsorbents in the removal of heavy metals from wastewater.
On the cement mortar-structured zeolite membrane:
1. Mechanical properties like compressive strength, permeability, among others should be evaluated in developing CMSZ membranes.
On the ED desalination system:
1. The effect of operating parameters like the thickness of CMSZ membrane, feed or salt concentrations, and flow rate should be explored
2. Fouling and scaling mechanisms on CMSZ membrane should be studied.
3. Investigations on the effect of various salt combinations on the removal of monovalent and divalent salts from binary and ternary salt solutions should be considered.
