1:45 PM - 3:15 PM
[O11-P52] Exploring the conditions for the formation of vivianite
Keywords:Vivianite, Gel process, Quality of water
1 Motivation
I like the mineral vivianite and want to investigate its formation by collecting and synthesizing it myself.
2 Previous research
Tracking the enigmatic vivianite ore (Ref.1) states that ‘Vivanite occurs near peat beds, which are a source of phosphoric acid’ and ‘Vivanite occurs near permeable beds, which supply iron’.
3 Objective
1) To investigate the formation conditions of vivianite in nature
2) To synthesize automorphic vivianite crystals
4 Hypotheses
1) Vivianite is produced along with biological remains
2) Automorphic crystals can be synthesized by gel method Crystals can be synthesized
5 Methods
5-1-1. Water quality survey
Instruments: pack test, water thermometer, pH meter, electrical conductivity meter
Procedure: water was collected in buckets and values of phosphate, nitrate nitrogen, iron, COD, water temperature, pH and electrical conductivity were measured.
5-1-2. Geological survey, analysis of sediment composition
Equipment: hammer, torsion toad, core sampler, hoe, etc.
Procedure: Vivianite and sediments were collected from outcrops in various parts of the prefecture, and mud from the moat was collected with a hoe. In addition, with the help of the University of Shiga Prefecture, we received boring cores from three sites at the bottom of Lake Biwa. The sediments were analyzed for elements by the Tor-Og method and SEM with the cooperation of Nagahama University of Biotechnology.
5-2. Vivianite synthesis experiment (detailed conditions are given in poster)
5-2-1. Preparation of silicate gel
Add (NH4)2HPO4 to 0.86M Na2SiO3 solution, stir, dispense into test tubes and neutralize with 1.0 M HCl. Then allow to stand for 24 hours.
5-2-2. Preparation of agar and gelatine gels
The ingredients were added to commercially available powdered agar and gelatine in the same way as in the preparation of silica gel and prepared as described on the respective packages.
5-2-3. Injection of aqueous FeSO4 solution
The aqueous FeSO4 solution is poured over the gel and sealed with Parafilm. For the high-pressure 5 atm experiment, the container is placed in a plastic bottle and connected to a compressor borrowed from the University of Shiga Prefecture. Experiments were conducted under various conditions.
6 Results and discussion
6-1. Water quality and geological survey sites
Water was collected at 26 sites in the prefecture, including 10 sites in the moat of Hikone Castle, and each value was measured. The results of seven characteristic sites for phosphoric acid, a raw material of vivianite, and electrical conductivity, an indicator of water quality, are shown below.
6-2. Geological survey results
Vivianite was collected at three sites in the prefecture. Nodules up to 10 cm or larger and granular aggregates several mm in size were collected. 18 sites in the prefecture (plus 3 borehole cores) were surveyed and a total of 133 samples analyzed. Details are given in the poster.
6-3 Synthesis experimental results
1) Crystals reaching a maximum size of 0.5 mm were obtained in 65 experiments.
The maximum crystal size of 0.5 mm was obtained in 65 experiments.
2) Elemental mapping by SEM confirmed that the resulting crystals were vivianite containing phosphorus and iron.
7. Discussion
1) Conditions for the formation of vivianite in nature
In this study, the survey results showed that phosphorus and phosphoric acid in the water and sediments in Shiga Prefecture are very low. In addition, all three sites where vivianite was produced were at the confluence of the Ado River and tributaries, and at the fan end, suggesting that a willing and continuous supply of phosphorus by running water may be necessary for the growth of vivianite.
2) Optimum gels and conditions for vivianite synthesis
Based on a total of 65 experiments, the following four conditions are considered optimal for the synthesis of large vivianite crystals.
1) The lower the raw material concentration, the better. 2) High temperature is better.
3) High pressure (5 atm) for silicic acid and atmospheric pressure for agar.
4) Add ascorbic acid to aqueous FeSO4 solution (ascorbic acid addition is only carried out with agar).
5) Agar is best among gels, and the synthesis period is shorter.
8. Future issues and prospects
・ We would like to compare and study whether running water is also involved in other vivianite producing areas.
・We would like to examine whether the crystal form can be controlled by additives such as ascorbic acid.
9.References
1. hasing the enigmatic vivianite! (Minerals occurring in freshwater mud layers), Science Club, Shiga Prefectural Katata High School.
2. Crystal growth in gels, Journal of the Crystallographic Society of Japan, Yuji Kachi.
I like the mineral vivianite and want to investigate its formation by collecting and synthesizing it myself.
2 Previous research
Tracking the enigmatic vivianite ore (Ref.1) states that ‘Vivanite occurs near peat beds, which are a source of phosphoric acid’ and ‘Vivanite occurs near permeable beds, which supply iron’.
3 Objective
1) To investigate the formation conditions of vivianite in nature
2) To synthesize automorphic vivianite crystals
4 Hypotheses
1) Vivianite is produced along with biological remains
2) Automorphic crystals can be synthesized by gel method Crystals can be synthesized
5 Methods
5-1-1. Water quality survey
Instruments: pack test, water thermometer, pH meter, electrical conductivity meter
Procedure: water was collected in buckets and values of phosphate, nitrate nitrogen, iron, COD, water temperature, pH and electrical conductivity were measured.
5-1-2. Geological survey, analysis of sediment composition
Equipment: hammer, torsion toad, core sampler, hoe, etc.
Procedure: Vivianite and sediments were collected from outcrops in various parts of the prefecture, and mud from the moat was collected with a hoe. In addition, with the help of the University of Shiga Prefecture, we received boring cores from three sites at the bottom of Lake Biwa. The sediments were analyzed for elements by the Tor-Og method and SEM with the cooperation of Nagahama University of Biotechnology.
5-2. Vivianite synthesis experiment (detailed conditions are given in poster)
5-2-1. Preparation of silicate gel
Add (NH4)2HPO4 to 0.86M Na2SiO3 solution, stir, dispense into test tubes and neutralize with 1.0 M HCl. Then allow to stand for 24 hours.
5-2-2. Preparation of agar and gelatine gels
The ingredients were added to commercially available powdered agar and gelatine in the same way as in the preparation of silica gel and prepared as described on the respective packages.
5-2-3. Injection of aqueous FeSO4 solution
The aqueous FeSO4 solution is poured over the gel and sealed with Parafilm. For the high-pressure 5 atm experiment, the container is placed in a plastic bottle and connected to a compressor borrowed from the University of Shiga Prefecture. Experiments were conducted under various conditions.
6 Results and discussion
6-1. Water quality and geological survey sites
Water was collected at 26 sites in the prefecture, including 10 sites in the moat of Hikone Castle, and each value was measured. The results of seven characteristic sites for phosphoric acid, a raw material of vivianite, and electrical conductivity, an indicator of water quality, are shown below.
6-2. Geological survey results
Vivianite was collected at three sites in the prefecture. Nodules up to 10 cm or larger and granular aggregates several mm in size were collected. 18 sites in the prefecture (plus 3 borehole cores) were surveyed and a total of 133 samples analyzed. Details are given in the poster.
6-3 Synthesis experimental results
1) Crystals reaching a maximum size of 0.5 mm were obtained in 65 experiments.
The maximum crystal size of 0.5 mm was obtained in 65 experiments.
2) Elemental mapping by SEM confirmed that the resulting crystals were vivianite containing phosphorus and iron.
7. Discussion
1) Conditions for the formation of vivianite in nature
In this study, the survey results showed that phosphorus and phosphoric acid in the water and sediments in Shiga Prefecture are very low. In addition, all three sites where vivianite was produced were at the confluence of the Ado River and tributaries, and at the fan end, suggesting that a willing and continuous supply of phosphorus by running water may be necessary for the growth of vivianite.
2) Optimum gels and conditions for vivianite synthesis
Based on a total of 65 experiments, the following four conditions are considered optimal for the synthesis of large vivianite crystals.
1) The lower the raw material concentration, the better. 2) High temperature is better.
3) High pressure (5 atm) for silicic acid and atmospheric pressure for agar.
4) Add ascorbic acid to aqueous FeSO4 solution (ascorbic acid addition is only carried out with agar).
5) Agar is best among gels, and the synthesis period is shorter.
8. Future issues and prospects
・ We would like to compare and study whether running water is also involved in other vivianite producing areas.
・We would like to examine whether the crystal form can be controlled by additives such as ascorbic acid.
9.References
1. hasing the enigmatic vivianite! (Minerals occurring in freshwater mud layers), Science Club, Shiga Prefectural Katata High School.
2. Crystal growth in gels, Journal of the Crystallographic Society of Japan, Yuji Kachi.