Development of Pillared Clays for Wet Hydrogen Peroxide Oxidation of Phenol and Its Application in the Posttreatment of Coffee Wastewater

Table 1

Bentonite-based catalysts for oxidation of phenol using Fenton-like AOPs.

Pillared bentonite	Year	Synthesis condition	Development	Reference
B-Fe[50]	2003	Pillaring solution: dilute; Suspension clay: 2 wt%; Time intercalation: 48 h	This is the first work using natural bentonite from Valle del Cauca.	[46]
B-Fe[100]
Al-Fe (10%)	2005; 2007	Pillaring solution: dilute; Suspension clay: 2 wt%; Time intercalation: 24 h	Addition of Ce during the synthesis of the catalysts show favorable results in; phenol oxidation.	[47–49]
Al-Ce-Fe (10%)
Al-Ce-Fe (5%)
Al-Ce-Fe (1%)
B-AlCe(10)Fe(10)	2008	Pillaring solution: dilute; Suspension clay: 2 wt%; Time intercalation: 24 h	The clay pillared with the Al-Ce-Fe mixed solution is a very active and selective catalyst in the phenol oxidation.	[50]
AlCe24US		Pillaring solution: dilute; Aging: 24 h or 10 min ultrasound (50 kHz); Suspension clay: 2 wt%; Time intercalation: 24 h or 10 min US	Ultrasound considerably reduces the modification time of the pillared clays. The catalysts show physical-chemical and catalytic properties similar to those when synthesizing by the conventional method.
AlCeUS24
AlCeFe24US	2008			[51]
AlCeFeUS24
AlCeFe2424
B1-AlFe		Pillaring agent: solid; Clay: powder; Intercalation: dialysis membrane; Time intercalation: 60 h	Using powdered clay and a solid pillaring agent, the water volume needed in the synthesis of pillared clays was reduced.
B2-AlFe	2008			[52]
B3-AlFe
AlCe (10%)		Pillaring agent: solid; Aging and intercalation: microwaves (160 W, 10 min) or ultrasound (50 kHz, 30 min); Clay: powder; Intercalation: dialysis membrane	The use of microwaves and ultrasound significantly reduces the synthesis time of pillared clays.
MAl-Fe
UAl-Fe	2009			[53]
AlCeFe (10%)
MAl-Fe-Ce
UAl-Fe-Ce
MAlFe(1),		Pillaring solution: dilute; Aging and intercalation: microwaves (160 W, 10 min) or; ultrasound (50 kHz, 30 min); Clay: powder	The use of microwaves and ultrasound significantly reduces the synthesis time of pillared clays.
MAlFe(10)
UAlFe(1)
UAlFe(10)
MAlCeFe(1-1)	2009			[54]
MAlCeFe(5-1)
MAlCeFe(10-10)
UAlCeFe(1-1)
UAlCeFe(5-1)
UAlCeFe(10-10)
B2R, BT21		Pillaring solution: dilute; Aging and intercalation: microwaves (160 W, 10 min); OH/metal: 2.0; Suspension clay: 2%, 3%, and 100%	The use of microwaves significantly reduces the synthesis time. Additionally, the use of a clay suspension (30%) and dry clay reduces the amount of water used in the synthesis.
B21, B22	2009			[55]
B301, B302
BD1, BD2
B-Al US		Pillaring agent: Solid; Clay: powder; Intercalation: dialysis membrane; Time intercalation: 30 min (ultrasound, 50 kHz)	With the methodology here used, the volume of water needed and the synthesis time of pillared clays were reduced.
B-AlFe(2) US
B-AlFe(5) US	2009			[56, 57]
B-AlFe(10) US
B-AlFe
B-AlCeFe