Fig 1.
The studied river, stream gage location, and population points in the river basin (background terrain map was used from Natural Earth public domain http://www.naturalearthdata.com).
Table 1.
Sampling stations and geographical locations on Gamasiab River, Iran.
Table 2.
Adsorbents modified using different solutions.
Fig 2.
Process overview of nano zeolite purification test process and design expert model.
Fig 3.
Changes of sulfate along the Gamasiab river.
Fig 4.
Changes of nitrate along the Gamasiab river.
Fig 5.
Changes in phosphate along the Gamasiab river.
Fig 6.
Changes in iron along the Gamasiab river.
Fig 7.
Amount of sulfate after and before purification.
Fig 8.
Adsorption rate by time.
Fig 9.
Results of removing sulfate and phosphate interactions.
Fig 10.
Sulfate and nitrate interaction.
Fig 11.
Sulfate and iron interaction.
Table 3.
Experiment design levels and factors for zeolite.
Table 4.
Design matrix and laboratory data for effective factors in removing sulfate by zeolite (%).
Table 5.
Results of ANOVA for the second-order model of sulfate removal by zeolite from laboratory data.
Table 6.
Validation results of multi-response optimization endpoints for sulfate removal by zeolite.
Fig 12.
Real and predicted data for zeolite.
Fig 13.
Disturbance curves of the effect of main parameters on sulfate removal by zeolite.
Fig 14.
Effect of pH and D/C on sulfate removal percentage by zeolite in the balance curve diagram.
Fig 15.
Three-dimensional (3D) diagram of sulfate ion removal percentage by zeolite by surface response method and influencing factors of pH and D/C.
Table 7.
Optimal maximum sulfate removal by zeolite points predicted in the software.
Fig 16.
Langmuir model for sulfate adsorption process by zeolite.
Fig 17.
Freundlich model for sulfate adsorption process by zeolite.