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Table 1 Contact angles and surface physicochemical properties determined for each of the studied suspensions

From: Surface physicochemical properties of selected single and mixed cultures of microalgae and cyanobacteria and their relationship with sedimentation kinetics

Microalgal suspensions

Contact angles (°)

Surface tension parameters and free energy of hydrophobic interaction (mJ m −2 )

Zeta potential (mV)

θ W

θ B

θ F

\( {\boldsymbol{\gamma}}_{\boldsymbol{s}}^{\mathbf{LW}} \)

\( {\boldsymbol{\gamma}}_{\boldsymbol{s}}^{\mathbf{AB}} \)

\( {\boldsymbol{\gamma}}_{\boldsymbol{s}}^{-} \)

\( {\boldsymbol{\gamma}}_{\boldsymbol{s}}^{+} \)

\( \varDelta {\boldsymbol{G}}_{\boldsymbol{sws}}^{\mathbf{TOT}} \)

Single cultures

         

C. vulgaris

46.5 ± 2.8 a

37.1 ± 1.5 a

61.0 ± 0.3 a

35.0 ± 1.5 a

0.0 ± 0.0 a

48.7 ± 6.9 a

0.1 ± 0.1 a

52.5 ± 14.3 a

−35.4 ± 0.4 a

M. aeruginosa

44.8 ± 5.5 a

37.1 ± 1.6 a

36.4 ± 8.4 b

35.9 ± 0.7 a

10.7 ± 2.8 b

57.4 ± 7.6 a

0.5 ± 0.4 a

43.4 ± 15.5 a

−40.0 ± 2.4 a

P. subcapitata

48.7 ± 1.1 a

37.3 ± 2.2 a

45.8 ± 3.6 b

35.8 ± 1.0 a

5.4 ± 1.5 b

35.9 ± 1.7 b

0.2 ± 0.2 a

13.8 ± 3.8 b

−48.1 ± 0.9 b

S. salina

51.9 ± 8.0 a

37.3 ± 1.0 a

73.6 ± 1.1 a

35.8 ± 0.4 a

0.0 ± 0.0 a

22.6 ± 3.2 b

0.0 ± 0.0 a

−10.2 ± 6.6 b

−43.1 ± 2.4 b

Mixed cultures

         

C. vulgaris + M. aeruginosa

41.9 ± 2.8 a

34.2 ± 4.4 a

51.6 ± 3.6 c

37.0 ± 1.8 a

0.5 ± 0.3 a

53.0 ± 8.9 a

0.0 ± 0.0 a

40.6 ± 11.8 a

−35.4 ± 1.0 a

C. vulgaris + S. salina

76.8 ± 4.2 b

35.3 ± 2.1 a

57.0 ± 3.1 c

36.6 ± 0.8 a

0.0 ± 0.0 a

52.2 ± 1.5 a

0.0 ± 0.0 a

40.1 ± 2.5 a

−45.1 ± 1.4 b

P. subcapitata + M. aeruginosa

41.9 ± 2.8 a

37.3 ± 0.9 a

35.5 ± 1.5 d

35.8 ± 0.4 a

11.7 ± 0.8 b

37.0 ± 4.8 b

0.9 ± 0.3 a

13.4 ± 7.2 b

−42.7 ± 1.4 b

C. vulgaris + P. subcapitata

57.0 ± 0.1 a

39.6 ± 0.1 a

56.0 ± 0.2 c

34.0 ± 0.1 a

0.0 ± 0.0 a

32.7 ± 0.3 b

0.0 ± 0.0 a

10.5 ± 0.5 b

−42.7 ± 1.5 b

P. subcapitata + S. salina

54.2 ± 1.9 a

37.6 ± 0.3 a

50.7 ± 1.1 c

35.6 ± 0.1 a

2.8 ± 0.5 c

32.0 ± 1.9 b

0.1 ± 0.0 a

8.3 ± 3.3 b

−40.5 ± 0.5 b

S. salina + M. aeruginosa

93.5 ± 3.3 c

35.0 ± 3.2 a

84.0 ± 1.3 a

36.7 ± 1.3 a

0.0 ± 0.0 a

7.6 ± 2.2 c

0.0 ± 0.0 a

−50.4 ± 8.6 c

−34.9 ± 1.0 a

  1. Values are presented as the mean ± standard deviation of two independent experiments. Different letters within the same column represent statistically different values (p < 0.05). θ W, contact angle with water; θ B, contact angle with α-bromonaphthalene; θ F, contact angle with formamide; \( {\gamma}_s^{\mathrm{LW}} \), Lifshitz-van der Waals component of the surface free energy; \( {\gamma}_s^{\mathrm{AB}} \), Lewis acid-base component of the surface free energy; \( {\gamma}_s^{-} \), electron donor component; \( {\gamma}_s^{+} \), electron acceptor component; \( \varDelta {G}_{sws}^{\mathrm{TOT}} \), free energy of hydrophobic interaction.