Table 3.

Correlation coefficient (R²) and rate constant (k) obtained by fitting the data of the release of protocatechuic acid from PANE and PAND nanocomposites into phosphate-buffered saline solution at pH 4.8, 5.3, and 7.4

Samples	pH	Saturation release (%)	R2			Pseudo-second ordera	Pseudo-first orderb	Parabolic diffusionc
			Pseudo-first order	Pseudo-second order	Parabolic diffusion
						Rate constant, k (mg/min)	Rate constant, k (min−1)	Rate constant, k (min−1)
PANE	7.4	59	0.9804	0.9989a	0.8860	2.2 × 10−5	–	–
PANE	5.3	82	0.9147c	0.8469	0.8517		4.9 × 10−4	–
PANE	4.8	85	0.9060	0.9601a	0.8334	4.1 × 10−5	–	–
PAND	7.4	83	0.9848	0.9910a	0.8266	2.3 × 10−5	–	–
PAND	5.3	87	0.9543	0.9652	0.9796c		–	3.1 × 10−2
PAND	4.8	98	0.9805b	0.8272	0.9563	–	2.1 × 10−3	–

Notes:

^arate release constant for pseudo-second order;

^brate release constant for pseudo-first order;

^crate release constant for parabolic diffusion.

Abbreviations: PAND, protocatechuic acid-Mg/Al nanocomposite synthesized by direct method; PANE, protocatechuic acid-Mg/Al nanocomposite synthesized by ion-exchange method.