As shown in Figure 1, the FTIR spectra of Na-rectorite sample. The band of 3640 cm⁻¹ corresponds to the frame work water stretching vibrations. At 1630 - 1640 cm⁻¹, there are the bands of flexing vibrations of free water at the edge of clay and in clay holes. The strong band at 1020 cm⁻¹ is attributed to Si-O stretching vibrations. Si-O-Al flexing vibration band occurs at about 486 cm⁻¹. The band at about 3440 cm⁻¹ is attributed to adsorbed water-flexing vibrations [25]. In the spectra of the nanocomposites, the N-H bonded to O-H vibration band at 3448 cm^–1 in CS shifts towards lower frequency [29], wider and stronger peaks are observed in all the REC/CS nanocomposites. This fact indicates that –NH₂ and –OH groups of CS formed hydrogen bonds with the –OH group in REC which coincided with the CS/MMT nanocomposites [30]. At 1420 cm⁻¹ (–NH deformation vibration in –NH₂), 1027 cm⁻¹ (–CO stretching vibration in –COCH₃), 2877 cm⁻¹ (C-H stretching vibration in CS) the peaks at these wave numbers were intact, indicating that the functional groups were not disturbed during the intercalation process. The appearance of all these peaks demonstrates that nanocomposites REC/CS (3:1) had been successfully prepared.

XRD patterns of unmodified REC and XRD pattern of nanocomposites with different REC/CS ratios of 5:1; 3:1 were collected from 0.7˚ to 10˚ (2q) and are show in Figure 2(a) and (c). It can be observed that unmodified rectorite exhibits 2q = 3.59˚ and the Dd_L value (the interlayer distance) is 2.45 nm, calculated by the Bragg’s equation [31]. In comparison with REC, the diffraction peaks of the composites rectorite shifted to the small-angle after being intercalated by chitosan, the results indicated that after the chitosan intercalated into the gallery of REC, a new composite material formed. It also can be observed from the Figure 2 that the layer spacing of the composite materials REC and the content of the chitosan was not proportional, when the ratio of amount of chitosan and REC is 1:5, the layer spacing has little change compared to REC merely, but when the ratio is 1:3, the layer spacing achieves to the maximum value of 2.78 nm. Then with the increase of amount of chitosan, the layer spacing is no longer increased, but even tends to decrease, the possible reason is when the content of chitosan is inadequate, the driving force is not enough to carry out the intercalation into the REC. On the contrary, if the content of the chitosan is too much, chitosan molecular structure would be twisted together and wrapped rectorites, resulting in a larger structure, making it difficult to enter the narrow layer of rectories, which make good effects can’t be achieved. So, as the figure shown, when the ratio is 3:1, the effect is best [28].

The SEM micrographs of REC, nanocomposite biosorbent (b) is shown in Figure 3. On the SEM of REC (Figure 3(a)), the surface is smooth, but appears porous. On the SEM of nanocomposite sorbent (REC/CS) (Figure 3(b)), the chitosan molecule was largely carried on

the surface of REC, therefore, the surface of the nanocomposite is microporous and have many active groups, But the other part was partly inserted into the REC layer spacing [31], getting through the interlayer hole of rectories, the fluffy surface of nano-composites making the surface area of nanocomposite increases, which increasing its adsorption capacity.

The TEM micrographs of nanocomposites were observed and are shown in (Figure 3(c)), it can be seen from the figure, rectories’ structure appears flaky and have many gaps between layers, the chitosan macromolecules distributed in these gaps, observing from TEM, the composite particle appears a size with diameter of tens to hundreds nanometer, so it can be concluded that the composites was nanocomposite materials. Water solution intercalation method directly embed the polymer into the inorganic layer and remove the solution by using appropriate solvent to dissolve polymer and clay, then mixed and stirred to obtain nanocomposites. It also can be seen from TEM analysis, the prepared rectorite/chitosan composites was nanocomposite materials, the result was consistent with the water solution interaction technique [28].

Figure 4 shows adsorption percent of CHCl₃ as a function of contact time onto four different adsorbents, namely rectories (a), chitosan (b), REC:CS 5:1 (c), REC/CS 3:1 (d), respectively. The saturation adsorption capacities of CHCl₃ onto the four adsorbents were measured as 25 mg·g^–1, 51 mg·g^–1, 73.6 mg·g^–1 and 81 mg·g^–1, respectively. The data indicated that the two REC/CS adsorbents showed higher adsorption capacities as compared with those of rectories and chitosan. On one hand, due to the intercalation of polymer chains usually increases the interlayer spacing relative to that of the pure REC [32], on the other hand, the introduction of chitosan, provided more available sites for CHCl₃ adsorption due to a larger surface and smaller pore diameter compared with rectories [33]. The phenomenon has been proved by the result of XRD and SEM analysis.

At the same time, it took 100 min, 80 min, 40 min and 50 min to attain equilibrium for rectories, chitosan, REC/CS 3:1 and REC:CS 5:1, respectively. The CHCl₃ removal increased dramatically and the adsorption equilibrium was achieved much faster with the introduction of chitosan. From the experimental data, it is observed that by introducing inorganic REC particles into the polymeric networks, the adsorption capacity seems to be affected significantly, especially in different time. This behavior is very clear. Nevertheless, one can conclude that this nanocomposite can be used in a wide short equilibration time.

Generally, the solution pH values are one of the important parameters controlling the adsorption of CHCl₃ from aqueous solution onto solid polymeric adsorbent [34]. In order to investigated effect of initial solution pH values on CHCl₃ removal, experiments were carried out using various pH levels in the range of 4.0 - 9.0, as shown in Figure 5. It appears that the adsorption percent of CHCl₃ onto 3:1 REC/CS decreased from 81.8% to 22.0% after 60 min adsorption with increase in pH from 4.0 to 9.0. This result indicated that the adsorption capacity decreased with the increase of initial solution pH. The decrease of chloroform adsorption with increasing pH can be explained by the electrostatic interaction between the adsorbent surface and the CHCl₃. Because chitosan has a positively charged surface below pH 6.5 (point of zero potential). In acidic solution, hydrogen atoms (H⁺) in solution can protonate amine groups (–NH₂) of chitosan. As a result, the electrostatic interactions between CHCl₃ and chitosan with positively charged surface increased in acidic solution [35].

Adsorption dosage is another important parameter because it determines the capacity of an adsorbent for a given initial concentration of adsorbate. Effect of adsorbent dosage was studied on CHCl₃ removal from aqueous solutions by varying the amount of 3:1 REC/CS from 0.1 g·L^–1 to 0.7 g·L^–1 while keeping other parameters constant such as 50 mg·L⁻¹ initial CHCl₃ concentration, initial solution pH 6.8 and stirring rate 120 rpm. The CHCl₃ removal increased from 12.1% to 81.2% with increasing adsorbent dosage from 0.1·g L⁻¹ to 0.7 g·L⁻¹ (Figure 6). Initially, a rapid increase of adsorption with the increasing adsorbent dosage was attributed to availability of more adsorption sites [36]. However, further increase in adsorbent dosage to 0.7 g·L⁻¹ only leads to the adsorption percent increase by 0.2%. At the same time, the amount adsorbed (q_e) decreased from 60 mg·g⁻¹ to 57.6 mg·g⁻¹ when the adsorbent dosage increased from 0.1 g·L⁻¹ to 0.7 g·L⁻¹. The decrease of adsorption was due to the concentration gradient between adsorbent and adsorptive [37]. As a result, 0.5 g·L⁻¹ was the optimum adsorbent dosage for CHCl₃ adsorption onto 3:1 REC/CS. This result was in agreement with the XRD analysis.