An Overview of Current and Prognostic Trends on Synthesis, Characterization, and Applications of Biobased Silica

Table 2

Composition of rice husk and rice straw ash by geographical location.

Chemical components	Composition in percent
	References
	[75]		[9]	[76]	[77]			[78]	[79]	[59]			[76]
	China		Indonesia	India	Cambodia	Italy	Vietnam	Egypt	Bangladesh	Brazil	Canada	Malaysia	India
	Rice straw	Rice husk	Rice straw	Rice husk	Rice husk	Rice straw	Rice straw	Rice straw	Rice husk				Rice husk
Silicon dioxide (SiO2)	73.26	94.79	84.60	80	80.18	83.20	50.68	57.90	89.86	92.9	97	93.1	22.12
Aluminium oxide (Al2O3)	0.25	0.36	—	3.93	0.83	0.33	0.14	1.00	0.73	0.18	0.4	0.21	1.23
Ferric oxide (Fe2O3)	0.49	0.86	0.16	0.41	4.29	3.57	0.43	1.00	1.28	0.43	0.4	0.21	1.28
Calcium oxide	4.46	0.75	0.88	3.84	1.55	1.60	6.14	2.30	0.91	1.03	0.49	0.41	1.24
Magnesium oxide (MgO)	2.14	1.86	0.44	0.25	0.81	1.00	2.32	3.40	1.16	0.35	0.50	1.59	0.21
Sodium oxide (Na2O)	0.93	0.39	—	0.67	—	—	—	—	—	0.02	1.12	—	—
Potassium oxide (K2O)	13.46	1.86	6.39	1.45	3.89	2.73	21.11	14.60	—	0.72	3.0	2.31	—
Manganese oxide (MnO2)	0.04	0.02	—	—	—	—	—	—	—	—	—	—	0.074
Phosphorus oxide (P2O5)	1.94	0.23	—	3.80	3.80	4.12	0.77	13.80	—	—	—	—	—
Sulfur trioxide (SO3)	2.41	0.09	—	0.78	2.05	1.52	2.14	3.20	—	0.10	0.24	—	—
Titanium oxide (TiO2)	0.05	0.02	—	—	—	—	—	—	—	—	—	—	—
Chlorine (Cl2)	0.57	0.08	—	—	—	—	—	2.30	—	—	—	—	—
Other components	—	—	7.53	2.60	2.60	1.92	—	0.50	—	—	—	—	—
Loss on ignition [80]	—	—	—	8.56	—	—	—	—	4.26	—	—	—	73.87