**2.7 Water samples**

*Trace Metals in the Environment - New Approaches and Recent Advances*

to 50 rpm for 25 min, and then left to settle for 1 h [29].

removal from water by *Moringa oleifera* press cake.

[33] and removing of Cd(II) from wastewater [34].

was left for 24 h for complete hydration of the kaolin [29].

shaker to 2, 1 mm, 500, 250, and < 250 μm.

**2.3 Synthetic water preparation**

**2.5 Atomic absorption spectrometer**

water treatment process.

**2.2 Leaves**

**2.4 Jar test**

30 min [35].

20,000, and 30,000 mg/L. The different concentrations were applied to wastewater, and jar test was performed with an initial speed of 150 rpm for 2 min, reduced

Method (b): oil was extracted by Soxhlet extraction method [29]. Extraction

Press cake preparation: the seeds were pressed mechanically by Mitomasa Sdn. Bhd., Kuala Lumpur, Malaysia, and the press cake was bought from the company and applied in water treatment [31]. Press cake was soaked with water overnight to get the remaining oil. And the clean press cake was used in this experimental work. The moisture content was calculated to get the right mass for the biosorbent added to water [31]. The synthetic turbid water was used for biosorption test on Cu(II)

*Moringa oleifera* leaves were collected from a nearby area at Universiti Malaysia Pahang, Kuantan, Pahang, Malaysia, dried and ground, and sieved using a sieve

*Moringa oleifera* leaf extract was used in aqueous solutions as a good sorbent for Pb(II) [32]. It was used for optimization of Cd(II), Cu(II), and Ni(II) biosorption

To prepare synthetic water, kaolin with laboratory grade (k7375-500G Sigma-Aldrich) was used, and 5 gm was dissolved in 500 ml of distilled water. Sodium bicarbonate solution was prepared by dissolving 100 gm of sodium carbonate (Hamburg Chemicals) in 1000 ml of distilled water to get a concentration of 100 mg/L. 500 ml of the sodium bicarbonate solution was added to kaolin solution and mixed at 200 rpm for 1 h to get uniform dispersion of kaolin particles which

Each beaker in jar test was filled with 500 mL of wastewater sample. 10 mL of *Moringa oleifera* press cake with different concentrations prepared were added into each beaker. The stirring speed was set at 200 rpm for 4 min followed by 40 rpm for

Atomic absorption spectrometer (AAnalyst 400, Perkin Elmer) was used to measure initial and residual heavy metal in treated water. Stock solution prepared from each standard at different concentrations was used to get calibration curve for

thimble is filled with 10 g of *Moringa oleifera* seed powder. Hexane solvent (170 mL) was poured into a round bottom flask. The heater is turned on until the solvent is boiling; the oil was extracted within around 45 min. *Moringa oleifera* cake residue was collected from the thimble and dried in an oven at 50°C overnight. Once the oil was fully removed from the *Moringa oleifera* seed, the seed cake residue could be used in water treatment [30]. The oil was extracted from the seeds because the presence of oil in the *Moringa oleifera* seed would affect the coagulation activity and heavy metal removal [19]. The higher the oil content in *Moringa oleifera* seed, the lower the performance of the *Moringa oleifera* cake residue in

**266**

The water samples of the Cu(II), Cd(II), Fe(II), Pb(II), and Cr(II) study were collected from "Sungai Baluk" river (Gebeng River {GR}), Gebeng Industrial Estate, Kuantan, Pahang State, Malaysia [30].

The synthetic water was prepared for measuring Cd(II) removal [10].
