Study on denaturation of laterite ores by La2O3 and CeO2 to treat arsenic and phosphate in water

enic adsorption equilibrium time of the material of nano-oxide La2O3 material is 120 minutes. The effect of pH on arsenic adsorption capacity of La2O3 nanomaterials in Figure 3.12, when the pH value changes from 2 to 7.1 the arsenic adsorption capacity of the material increases and the adsorption capacity decreases at pH 7.1 to 9. Effect of material concentration on arsenic adsorption capacity Đường đẳng nhiệt hấp phụ Lăngmuir r^2=0.979431 DF Adj r^2=0.97061571 FitStdErr=13.798889 Fstat=190.46738 Qmax = 210,05 mg/g b = 0,059 0 50 100 150 Nồng độ ion phốt phát còn lại Cf (mg/l) 0 50 100 150 200 250 D un g lư ơṇ g hấ p ph u ̣ ph ốt p há t q (m g/ g) 0 50 100 150 200 250 D un g lư ơṇ g hấ p ph u ̣ ph ốt p há t q (m g/ g) 6 Figure 3.13. Arsenic isothermal adsorption lines of La2O3 nanomaterials From the experimental results and using the Table-curve calculation software regression calculations the arsenic adsorption experimental results of La2O3 nanomaterials showed that Qmax = 81.47mg/g with regression coefficient r 2 = 0.98. The adsorption process follows the Langmuir isothermal adsorption equation. 3.2. Synthesis of CeO2 nanomaterials and evaluation of phosphate and arsenic adsorption capacity 3.2.1. Synthesis of CeO2 nanomaterials Selection of the sample calcination temperature to form the CeO2 phase 20 30 40 50 60 70 80   650 o C 550 o C 450 o C 180 o C In te n ci ty ( a. u ) 2 Theta (degree)  CeO2 Figure 3.14. DTA-TGA thermal analysis diagram of Ce(NO3)4/gelatin Figure 3.15. XRD patterns of Ce (NO3)4 gel at different temperatures. Results of DTA thermal analysis diagram from Figure 3.14 and results of XRD analysis calcined at different temperatures in Figure 3.15 of the gel sample Ce(NO3)4/gelatin showed that CeO2 nanomaterials synthesized at temperature 550 o C. The effect of pH on gel creation process on the formation of CeO2 phase Results of X-ray diffraction analysis in Figure 3.16 show that pH 3 is the synthetic pH of CeO2 nanomaterials in subsequent studies. Results on XRD diagram of CeO2 nanomaterials synthesized at different gel forming temperatures. The results showed that at gel forming temperatures did not affect the formation of CeO2 phase. The resulting gel-making temperature at 80°C was selected to synthesize the CeO2 nanomaterial. 7 20 30 40 50 60 70 80  pH 1 pH 2 pH 3 pH 4 In te n c it y ( a .u ) 2 Theta (degree)  CeO2 20 30 40 50 60 70 80 120 o C 100 o C 80 o C 60 o C I n te n c it y ( a .u ) 2 Theta (degree) 40 o C  Figure 3.16. XRD diagram of sample CeO2 nanomaterial at different pH Figure 3.17. XRD pattern of gel forming CeO2 nanomaterials at different temperatures Morphology and structure of CeO2 material nh 8. Ảnh E của m u vật liệu nano CeO2 Results of analysis of CeO2 nanomaterials with TEM images showed that the sample material is relatively uniform in size, has a spherical shape with an average size <30 nm. The material has many hollow structure. The specific surface area of CeO2 nanomaterials was determined by the BET method which was obtained with value of 56.1 m 2 /g. The zero-charge point of nanomaterial CeO2 Figure 3.19. The zeta potential of CeO2 nanomaterials The results obtained in Figure 3.19 were CeO2 nanomaterials with pHpzc value of 6.7. 3.2.2. Evaluate the phosphate and arsenic adsorption on CeO2 nanomaterials Results of adsorption of phosphate material to nano CeO2 Phosphate adsorption equilibrium time with CeO2 nanomaterials Table 3.7. Effect of phosphorus adsorption equilibrium time by CeO2 nanomaterials. 8 t (min) Co (mg/l) Cf (mg/l) q (mg/g) Adsorption performance H(%) 30 10.01 5.52 8.96 10.4 60 10.10 3.72 12.5 62.5 90 9.99 3.45 13.04 65.5 120 10.0 3.45 13.10 65.5 The results of the study in Table 3.7 showed that the phosphate adsorption capacity increases with time and the phosphate adsorption equilibrium time of CeO2 nano-oxide material at 90 minutes. Effect of pH on phosphate adsorption Figure 3.20. Effect of pH on phosphate adsorption capacity on CeO2 nanomaterials The results in Figure 3.20 showed that the adsorption of phosphate on CeO2 nanocomposites was highly dependent on the pH value of the solution. pH from 2 to 6.7 phosphate absorption capacity increased from 32.5 mg/g to 45.8 mg/g and pH from 6.7 to 9 phosphate absorption capacity decreased from 45.8 mg/g to 35.1 mg/g. Phosphate adsorption capacity by CeO2 nanomaterial Figure 3.21. Isothermal phosphate adsorption lines of CeO2 nanomaterials Using Table - curve calculation software to regress regression results of phosphate adsorption on CeO2 nanomaterials showed that Qmax = 152.66 mg/g with regression coefficient r 2 = 0.99. The adsorption process follows the Langmuir isothermal adsorption equation. FT-IR spectrum analysis of CeO2 nanomaterials before and after phosphate adsorption 9 4000 3500 3000 2500 2000 1500 1000 b a I n t e n c it y ( a .u ) Number of waves (cm -1 ) 1114.47 1146.15 1647.27 1058.56 1107.23 2927.82 Figure 3.22. FT-IR superposition of CeO2 nanomaterials. b) pre-adsorption of phosphate; a) after phosphate adsorption Through FT-IR spectrum results of CeO2 nanomaterials, before and after adsorption of phosphate (Figure 3.22a, 3.22b), there were 3480 cm -1 wave numbers typical for the valence of –OH group on the material surface, 1647 cm -1 wave numbers assigned to water molecules (H-O-H) and wave numbers 1114 cm 1- , 1146 cm 1- typical for the group - OH associated with the material. In the presence of PO4 3- on FT - IR spectrum after phosphate adsorption material has substituted - OH into a new peak of 1058 cm -1 . It is shown that CeO2 nanomaterial can adsorb phosphate by complex mechanism on the surface of the material. Arsenic adsorption results of CeO2 nanomaterials Investigation of arsenic adsorption equilibrium time of CeO2 nanomaterials Figure 3.23. The arsenic concentration remained after the reaction over time The analysis results in Figure 3.23, the relationship between reaction time and arsenic concentration after reaction showed that the adsorption process occurred quickly in the first 90 minutes and reached equilibrium at 120 minutes. Therefore, 120 minutes is taken as the time to reach arsenic adsorption equilibrium for further studies Effect of pH Figure 3.24. Effect of pH on arsenic adsorption The results of analyzing the effect of pH on arsenic adsorption capacity on CeO2 nanomaterials are similar to arsenic adsorption on La2O3 nanomaterials. When the pH value changes from 2 to 6.7, the arsenic adsorption capacity of the material increases and the adsorption capacity decreases when the pH is from 6,7 to 9 Determining the maximum arsenic adsorption capacity of CeO2 nanomaterials 10 Figure 3.25. Arsenic isothermal adsorption lines of CeO2 nanomaterials Using Table - curve calculation software to regress regression results of arsenic adsorption on CeO2 nanomaterials showed that Qmax = 45.07 mg/g with regression coefficient r 2 = 0.99. The adsorption process follows the Langmuir isothermal adsorption equation. 3.3. Synthesis of La2O3-CeO2 mixed-oxides nanomaterials and evaluation of phosphate and arsenic adsorption capacity 3.3.1. Synthesis of nano materials La2O3-CeO2. Results of thermal analysis for selection of sample calcination temperature Figure 3.26. Thermal analysis diagram of gen sample La(NO3)3-Ce(NO3)4/gelatin Figure 3.27. X-ray diffraction diagram of gel sample La(NO3)3-Ce(NO3)4/Gelatin at different temperatures Results of DTA thermal analysis diagram from Figure 3.26 and results of XRD analysis at different temperatures in Figure 3.27 of the La(NO3)3-Ce NO3)4 gel sample, the La2O3-CeO2 nanomaterial was synthesized at 550 o C. Effect of pH and gel forming temperature on the formation of La2O3-CeO2 phase Figure 3.28. The XRD diagram of the sample (La2O3-CeO2) was made at different gel forming temperatures. Figure 3.29. XRD diagram of nano material La2O3-CeO2 sample was synthesized at different pH. The results of X-ray diffraction analysis in Figure 3.29 showed that pH 4 is the synthetic pH of La2O3-CeO2 nanomaterials in subsequent studies.. 11 Results on the XRD patterns of nano materials La2O3-CeO2 made at different gel forming temperatures in Figure 3.28, gel forming temperature at 80°C were selected to synthesize La2O3-CeO2 nanomaterials. Investigate the metal ratio on gelatin to the process of forming La2O3-CeO2 phase Figure 3.30. The XRD patttern of metal-to-metal (La2O3-CeO2)/gelatin at different ratios The process of studying the effect of molar metal to gelatin ratio, The author conducted the molar ratio of La(NO3)3/Ce(NO3)4, which is 1/1, molar ratio (La(NO3)3 - Ce(NO3)4) / gelatin, respectively. 1/2; 1/3; 1/1; 2/1; 3/1. The author chose the ratio (La(NO3)3-Ce(NO3)4)/gelatin as 1/1 for further research. Morphology of nano materials La2O3-CeO2 nh . TEM image of La2O3-CeO2 nanomaterial Results of characteristic morphological analysis of surface of nanomaterials La2O3 - CeO2 by TEM image showed that the material has a spherical shape with relatively uniform size <50 nm. Clarify the structure of materials that determine the specific surface area according to the BET method. Analytical results for SBET = 78 m 2 /g. 3.3.2. Characteristics of La2O3-CeO3 nanomaterials when adsorbed phosphate and arsenic Research results of zero charge point of La2O3-CeO2 nanomaterials Figure 3.32. pHpzc value of nano materials La2O3-CeO2 The results in Figure 3.32 showed that the pHf value intersects with the pH value at the point Δp 5 8 So La2O3- CeO2 nano material has a pHpzc value of 5.8. Characteristics of La2O3-CeO2 nanomaterials when phosphate adsorption. X-ray scattering spectrum (EDS) of nano-material La2O3-CeO2 before and after phosphate adsorption -2 -1 0 1 2 3 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.51010.5 ∆p i pH i 12 a) b) Figure 3.33. X-ray scattering spectrum (EDS) of nano-material La2O3-CeO2 a) before and b) after phosphate adsorption Results of X-ray scattering (EDS) analysis of La2O3-CeO2 nanomaterials before and after adsorption are all presented with La, Ce and O components. Results of X-ray scattering (EDS) analysis of La2O3-CeO2 nanomaterials before phosphate adsorption did not show the presence of phosphate. Materials after adsorption of phosphate showed P and O appearances, as a result of phosphate adsorption on the surface of La2O3-CeO2 nanomaterials. Results of FT-IR spectrum analysis of La2O3-CeO2 materials before and after phosphate adsorption Figure 3.34. FTIR of nano-materials La2O3-CeO2.a) before adsorption; b) after phosphate adsorption FT-IR analysis of La2O3-CeO2/gelatin nanomaterials before phosphate adsorption was found to have wave values of 3421 cm -1 assigned to the covalent oscillation characteristic of – OH. The peak at 1118 cm-1 is assigned to the –OH group valence oscillation associated with La2O3-CeO2 nanomaterials, when PO4 3- adsorbed, the material has a new characteristic peak for PO4 3- instead of - OH at 1060 cm -1 . Raman spectrum of nano-material La2O3-CeO2 before and after phosphate adsorption 13 Figure 3.35. Raman spectrum of nano materials La2O3-CeO2 a) before adsorption; b) after phosphate adsorption Figure 3.35 showed Raman analysis results of La2O3-CeO2 nanomaterials before and after phosphate adsorption. the figure showsed that Raman spectra before adsorption of phosphate, the materials have peaks of 1510 cm -1 and 1350 cm -1 , which are typical for group oscillation of -OH on material surface. Materials after adsorption of phosphate indicated that peaks of 1045 cm -1 and 1058 cm -1 are new characteristic for phosphate elements, proving that the materials have the ability to adsorb phosphate on the surface of the materials.. Characteristics of La2O3-CeO2 nano materials when arsenic adsorption X-ray scattering spectrum (EDS) of La2O3-CeO2 nanomaterials before and after arsenic adsorption a) b) Figure 3.36. EDX spectrum of nano materials La2O3-CeO2 a) before adsorption; b) after arsenic adsorption Results of X-ray scattering spectroscopy (EDS) in Figure 3.36 of La2O3-CeO2 nanomaterials before and after adsorption are all present with La, Ce and O components. Results of X-ray scattering (EDS) analysis of La2O3-CeO2 nanomaterials before arsenic adsorption were not found in the presence of arsenic. Materials after arsenic adsorption see arsenic appeared in Figure 3.36b. FT-IR analysis results of La2O3-CeO2 nanomaterials before and after arsenic adsorption 14 Figure 3.37. FT-IR spectrum of nano materials (La 3+ -Ce 4+ )/gelatin b) before arsenic adsorption, a) after arsenic adsorption FTIR analysis results of materials before and after arsenic adsorption are shown in Figure 3.37. Material La2O3-CeO2 before and after adsorption appears with peaks at 3421 cm -1 and 3321 cm -1 , which is typical for the valence of the group - OH of water on the surface of the material. The peaks at 1639 cm -1 , 1464 cm -1 , which are specific for the H - O - H group valence oscillation associated with the material. The peaks at 1118 cm -1 , 1067 cm -1 typical for group oscillation - OH associated with nano-material La2O3-CeO2 (MOOH Bonding with metals La and Ce) Raman spectrum of La2O3-CeO2 nano-mixed oxides material before and after arsenic adsorption Hình 3.38. Phổ Raman của vật liệu nano La2O3-CeO2 b) trước hấp phụ; a) sau hấp phụ asen Figure 3.38 showed the Raman analysis results of La2O3-CeO2 nanomaterials before and after arsenic adsorption. In Figure 3.38b, the material has peaks of 1008, 1088, 1350, 1510 and 1448 cm -1 which is typical for H - O - H and - OH oscillations. Materials after adsorption of arsenic found that the material has a new peak peak of 831 cm -1 which is explained by the replacement of group - OH by group - O - As on the surface of the material. 3.3.3. Results of adsorption of phosphate and arsenic of nanomaterial La2O3-CeO2 Phosphate adsorption results of La2O3-CeO2 nanomaterials Phosphate adsorption equilibrium time Table 3.9. Effect of phosphate adsorption equilibrium time by nanomaterial La2O3-CeO2 t (min) Co (mg/L) Cf (mg/L) q (mg/g) 30 9.99 3.41 10.08 60 10.02 3.41 10.08 90 10.05 3.06 11.88 120 10.02 3.06 11.88 Table 3.9 showed that the phosphate adsorption capacity increases with the first 60 minutes, at 90 minutes and 120 minutes the phosphate adsorption capacity of La2O3-CeO2 15 nanomaterials changes insignificantly. Therefore, the adsorption equilibrium time is 90 minutes, which is used to study the later experiments Effect of pH on phosphate adsorption capacity Figure 3.39. Effect of pH on phosphate adsorption capacity on La2O3-CeO2 nanomaterials The results shown in Figure 3.39 show that the adsorption of phosphate on La2O3-CeO2 nanomaterials is highly dependent on the pH value of the solution. In the pH range of 2 to 5.8, the phosphate adsorption capacity increases. When the pH is between 5.8 and 9, the phosphate adsorption capacity decreases Effect of initial phosphate concentration on the adsorption capacity of La2O3-CeO2 nanomaterials Figure 3.40. Phosphorus adsorption isotherm of nanomaterials La2O3-CeO2 Using Table - curve calculation software to regress regression results of phosphate adsorption on nanomaterials La2O3-CeO2 showed that Qmax = 123.74 mg/g with regression coefficient r 2 = 0.98. The adsorption process follows the Langmuir isothermal adsorption equation Results of evaluating the influence of competitive factors on phosphate adsorption of nano- materials La2O3-CeO2. Table 3.10. Effect of Fe(III), Mn(II), SO4 2- , Cl - on phosphate adsorption capacity on nano- materials La2O3-CeO2 1 Fe(III) Concentration (mg/L) 0 10 20 30 - Adsorption capacity phosphate q (mg/g) 49.64 55.27 62.51 67.34 2 Mn(II) Concentration (mg/L) 0 0,5 1,0 5 - Adsorption capacity phosphate q (mg/g) 49.64 64.12 65.73 68.14 - 3 SO4 2- Concentration (mg/L) 0 50 100 200 250 Adsorption capacity phosphate q (mg/g) 47.76 47.66 47.66 47.66 47.66 4 Cl - Concentration (mg/L) 0 100 150 200 250 Adsorption capacity phosphate q (mg/g) 49.64 44.53 40.25 33.83 31.69 16 The results in Table 3.10 showed that when Fe(III) concentration increases, the ability of phosphate adsorption of materials increased. Similarly, the effect of Fe(III), when Mn(II) concentration increases, the material ability to adsorb phosphate increased. For SO4 2- the results in table 3.10 showed that increasing SO4 2- concentration did not significantly affect the phosphate adsorption capacity of the material. Regard to Cl - ion, the results in the table 3.10 showed that, when the Cl - concentration increased, the phosphate adsorption capacity of the material decreased. Kinetic modeling of phosphate adsorption Figure 3.41. a) First order kinetic odsorption; b) The second order kinetic of phosphate adsorption on nanomaterial La2O3-CeO2 Table 3.11. Some parameters of the first order kinetic equation of phosphate adsorption on nanomaterial La2O3-CeO2 Concentration photphat (mg/l) First order reaction k1 (min -1 ) R 2 χ2 qtn (mg/g) qlt (mg/g) 5 2.16 ×10 -2 0.952 0.0169 9.4 4.58 10 2.99 ×10 -2 0.934 0.0153 17.04 3.98 Table 3.12. Some parameters of the second order kinetic equation of phosphate adsorption on nanomaterials La2O3-CeO2 Concentration photphat (mg/l) Second order reaction k2 (g/mg.phút) R 2 χ2 qtn (mg/g) qlt (mg/g) 10 4.67×10 -2 0.999 0.1 9.4 10.00 10 1.51×10 -2 0.999 0.05 17.04 17.54 Research results of phosphate adsorption kinetics in Table 3.11 (first-order kinetic model) and Table 3.12 (second-order kinetic models) find that the correlation value R 2 = 0.999 of the second-order kinetic model larger than the first order kinetic model with R 2 = 0.952 and R 2 = 0.934 with this thesis conditions. Thus, phosphate adsorbed on nanomaterial La2O3-CeO2 follows the apparent second-order kinetic equation. Arsenic adsorption results of nano materials La2O3-CeO2 Effect of arsenic adsorption equilibrium time by nano-material La2O3-CeO2 17 Figure 3.42. The concentration of arsenic and reaction time Analysis results showed in Figure 3.42, the relationship of reaction time and arsenic concentration after reaction showed that the adsorption process occurred quickly in the first 90 minutes and reached equilibrium at 120 minutes. Effect of pH on arsenic adsorption Figure 3.43. Effect of pH on arsenic adsorption capacity The analysis of the effect of pH on arsenic adsorption capacity on nano materials La2O3-CeO2 found that when the pH increased from 2 to 5.8 arsenic adsorption capacity on the material increased from 18.4 mg/L to 19.52 mg/L and the adsorption capacity decreased from 19.52 mg /L to 12.4 mg/L at pH values from 5.8 to 9. Arsenic adsorption capacity by nanomaterial La2O3-CeO2 Figure 3.44. Arsenic adsorption isotherm of nanomaterials La2O3-CeO2 Using Table-curve calculation software to regress regression results of arsenic adsorption on La2O3-CeO2 nanomaterials. The result showed that Qmax = 90.06 mg/g with regression coefficient r 2 = 0.99. The adsorption process follows the Langmuir isothermal adsorption equation Results of evaluating the interference ion on arsenic adsorption process of the material. Table 3.13. Effect of Fe(III), Mn(II), SO4 2- , Cl - on arsenic adsorption capacity nano materials La2O3-CeO2 1 Fe(III) Concentration (mg/L) 0 5 7 10 - Adsorption capacity q (mg/g) 1.76 1.82 1.94 2.04 18 2 Mn(II) Concentration (mg/L) 0 5 7 10 - Adsorption capacity q (mg/g) 1.76 1.82 1.90 2.02 - 3 SO4 2- Concentration (mg/L) 0 50 100 200 150 Adsorption capacity q (mg/g) 1.76 1.76 1.76 1.74 1.74 4 Cl - Concentration (mg/L) 0 50 100 250 - Adsorption capacity q (mg/g) 1.76 1.45 1.12 1.02 - The results of table 3.13 showed that when the concentration of Fe(III) changed from 0 to 10 mg/L, the arsenic adsorption capacity of nanomaterial La2O3-CeO2 increased from 1.76 mg/g to 2.04 mg/g. For Mn (II), when the concentration of Mn (II) was increased, the arsenic adsorption capacity of La2O3-CeO2 nanomaterial also increased. This phenomenon is because Mn (II) in the solution can oxidize As (III) to As (V) which is better adsorption on materials. With ion SO4 2- the result in table 3.13 showed that arsenic adsorption capacity decreases with increasing concentration SO4 2- but the concentration is negligible. Thus, ion SO4 2- does not significantly affect the arsenic adsorption capacity in the range of used concentration. The results of table 3.13 also showed that Cl - ion interfere arsenic adsoption capacity of material. The Cl - concentration increases from 0 to 250 mg/L reduced the arsenic adsorption capacity of La2O3-CeO2 nanomaterial from 1.76 mg/g to 1.02 mg/g. Arsenic adsorption kinetics Kinetic model of arsenic adsorption Figure 3.45. a) First order kinetics graph of arsenic adsorption on nanomaterials La2O3- CeO2 Figure 3.45. b) The second order kinetic model of arsenic adsorption on nanomaterials La2O3-CeO2 Table 3.14. Parameters of the first order kinetic equation of arsenic adsorption on La2O3-CeO2 nanomaterials Concentration asen (mg/l) First order reaction k1 (min -1 ) R 2 χ2 qtn (mg/g) qlt (mg/g) 5 2.76×10 -2 0.967 0.014 9.48 3.90 10 4.15×10 -2 0.978 0.017 1.99 7.36 Table 3.15. Parameters of the quadratic kinetic equation of arsenic adsorption on La2O3-CeO2 nanomaterials Concentration Second order reaction 19 asen (mg/l) k2 (g/mg.phút) R 2 χ2 qtn(mg/g) qlt(mg/g) 5 4.67×10 -2 0.99 0.10 9.48 10.00 10 1.21×10 -2 0.99 0.05 18.90 19.61 The results of arsenic adsorption kinetics in Table 3.14 (first-order kinetic model) and Table 3.15 (second-order kinetic models) showed that the correlation value R 2 = 0.999 of the second-order kinetic model larger than the first order kinetic model with R 2 = 0.967 and R 2 = 0.978 in the survey conditions. 3.4. Research on manufacturing La2O3-CeO2 nanomaterials on laterite carriers in applying phosphate and arsenic adsorption in water. 3.4.1. Research on manufacturing La2O3-CeO2 nanomaterials on laterite carriers 3.4.1.1. Study on the ratio of La2O3-CeO2 nanomaterials on laterite affecting arsenic and phosphate adsorption From the above research results, we have three type of materials and each material can be characterized by three factors which are adsorption capacity, surface area, and porousity volume. The summerize result was conducted in table 3.16. Based on the obtained results, we selected La2O3-CeO2 nanocomposite materials to study denaturation on laterite and application of phosphate and arsenic treatment in water. Table 3.16. The adsorption capacity of arsenic, phosphate and material structure is synthesized ST T Material name Qmax(mg/g) Surface area SBET (m 2 /g) Empty volume (cm 3 /g) Hole size (nm) Asenic phospha te 1 nanomaterial La2O3 81.47 210.05 37.80 0.005 19.962 2 nanomaterial CeO2 45.07 152.66 56.10 0.082 16.323 3 nano-mixed oxdies La2O3-CeO2 90.06 123.74 78.00 0.167 8.629 Table 3.17. Coating efficiency and lanthanum, cerium content on laterite carriers ST T Cont ent La2O 3- CeO2 origi nal (%) Cont ent La fixed on lateri te (%) Cont ent Ce fixed on lateri te (%) Cont ent La- Ce fixed on lateri te (%) Efficie ncy (%) 1 2 0.43 0.51 0.94 47 2 3 0.91 1.10 2.01 67 3 5 1.58 1.77 3.06 67 4 7 2.32 2.41 4.73 67.5 Table 3.18. Results of adsorption of phosphate and arsenic of nano-material La2O3-CeO2/laterite at different coating rates ST T Percent age covere d on laterite (%) Adsor bent Initial concentr ation C0(mg/l) Concentr ation remainin g Cf (mg/l) Adsorp tion capacit y q (mg/g) 1 2 Phosp hate 25 21.55 6.9 Asenic 25 21.4 7.2 2 3 Phosp