**3. Results and discussion**

### **3.1. Introduction**

The algal material was modified with an amino compound to improve its thermal stability [9]. The resulting product obtained was a water-insoluble solid material. The raw and the modified products were characterized using FTIR to obtain the functional groups present; sorption parameters were established and then used for adsorption experiments in both synthetic solutions and real water samples.

### **3.2. FTIR analysis of modified and unmodified algae**

The modified and unmodified materials were characterized with FTIR, and the resulting spectra are presented in **Figure 1**.

**Figure 1.** FTIR spectrum of unmodified algae.

The results show the presence of many functional groups capable of metal sorption. The broad and strong band at 3400.3 cm−1 could be attributed to either ─OH or ─NH group [25]. The band at 2927.72 cm−1 was assigned to C─H stretches, while the band at 1651.0 cm−1 was assigned to stretching ─OH, C═O or N═C [25] .The band at 1380.9 cm−1 confirms the presence of an amide group of an amide or sulphamide group [26, 27]. The material was modified with tetramethylethylenediamine, and results obtained are presented in **Figure 2**.

Upon modification, the band at 3400.3 cm−1 that was attributed to the ─NH of an amide shifts to a lower value of 3394.5 cm−1. The intensity of the band also decreases. This can be attributed to suppression influenced by the carbon atoms from anchored tetramethylethylenediamine functional groups. Similar observations were reported by Schluter [28] as he studied the treatment of poly(1.1.1)propellane with lithium organic initiators and then investigated its rigidity. Mwangi and Ngila [29] also recorded the same observation when studying the removal of heavy metals from contaminated water using ethylenediamine-modified green seaweed. New bands are also seen to appear at 1454.2 cm−1 and 2597 cm−1. The band at 1454.2 cm−1 can be attributed to an NO2 group and that at 2597 cm−1 can be attributed to an additional ─OH groups from a phenolic compound. Both the parent and the modified material were applied for sorption experiments.

**Figure 2.** FTIR spectrum of modified algae.
