Table 5.

Comparisons of methodology and findings in this study with other existing studies

No	References	Type of adsorbent	Metal nanoparticles (MNPs)	Removal of MB	Findings
1	This study	Activated carbon synthesised from durian skin (AC-DS) Study the effects of reaction conditions	AgNPs were synthesised with stabilisers (polyvinylpyrrolidone and citrate) Comparing the effects of different types of stabilisers Content of Ag was less 0.5% (less than 1%) based on SEM–EDS	Used 10 mg of AC-DS with and without AgNPs 1.5 mL of 0.2 g/L of MB used for adsorption test of AC-DS 0.5 mL of 0.125 g/L of MB used for recyclability test Catalytic oxidation reaction using H2O2 was used for catalytic degradation of MB	More than 90% removal of MB by the AC-DS About 50% improvement to recyclability of AC-DS when incorporated with AgNPs/Citrate (77% removal of MB after second cycle)
2	[46]	Commercial granular AC purchased from Tra Bac Company	AgNPs synthesised with starch as stabiliser 0.65 wt % of Ag based on EDS	MB (25 mL; 100, 500 and 1000 mg/L) and AgNPs-AC (50, 250, 500 mg) used for the adsorption test Adsorption isotherm was studied	Achieved up to 90% removal of MB
3	[47]	AC from coconut shell	AgNPs and TiONPs 11.6 wt % of Ag in the nanocomposite	MB (10–50 mg/L) and CSAC@AgNPs@TiO2NPs (50 mg) used for adsorption test Effects of adsorption parameters and adsorption kinetics were studied Recyclability/reusability was studied	More than 85% removal of MB after 6 cycles
4	[48]	AC synthesised from residue-coconut husk	AgNPs synthesised by sono-electrochemical method Average size of AgNPs was 23 nm	MB (100–500 mg/L; 200 mL) and AgAC (0.2 g) used for adsorption test	70% removal of MB
5	[42]	AC synthesised from cashew nutshell (CNSAC)	AgNPs synthesised using in-situ reduction on the CNSAC Content of Ag in the nanocomposite was 3.04 wt % based on EDX	MB (100 mL; 50 mg/L) and catalysts (0.2 g/L)	Removal of MB was 98.3% after 120 min
6	[15]	Commercial AC purchased from Merck	Comparing AgNPs and PdNPs The AgNPs and PdNPs were synthesised by in situ reduction method without the addition of stabilisers/ligands Size of AgNPs (15 nm–80 nm) Content (wt or atomic %) of Ag on AC was unknown	Study the effect of parameters (pH, adsorbent weight, contact time, initial dye concentration) in the adsorption of MB Study the adsorption isotherm and kinetics	Adsorption of MB onto AgNPs-AC and PdNPs-AC follows Langmuir model and second order kinetic model About 95% removal of MB by AgNPs-AC
7	[18]	Polymer-based adsorbent (Polystyrene-divinylbenzene mesoporous microsphere)	AgNPs synthesised by in-situ reduction method without the addition of stabilisers/ligands Content of AgNPs was about 25.48 wt % by thermogravimetric analyses	1 mg of micropsheres and 2 mL of 0.15 mM MB used for adsorption test Catalytic reduction reaction using NaBH4 was used for catalytic removal of MB	Efficiency of 97.12% removal of MB even after 5 cycles of adsorption test
8	[19]	Silica (SG)	AgNPs, synthesised by in-situ reduction with Cicer arietinum pod extract as biogenic Effect of light to the catalytic activity of AgNPs-silica (Ag@SG) was studied AgNPs with spherical structure with size ranging from 6 – 14 nm AgNPs content on SG was unknown	50 mg Ag@SG and MB (50 ppm; 20 mL) was used for dark adsorption test 50 mg Ag@SG and MB (40 ppm; 50 mL) was used for photo adsorbent test Catalysis reaction without addition of oxidant or reductant Amount of catalysts, MB concentration and time were studied for the adsorption test	88% removal of MB by photodegradation by Ag@SG as compared to AgNPs and SG alone
9	[9]	Periwinkle shelled-hyroxyapatite (HAP)	AgNPs synthesised with Terminalia cattappa capping agents Rod-shape of AgNPs Content of AgNPs was about 7.7% (unknown basis of percentage)	AgNPs-HAP (0.5 g) and MB and Congo red (50 mL; 50 mg/L) used for adsorption test Influences of adsorption parameters and adsorption isotherm were studied Reusability/recyclability was also studied	Over 80% of percentage of dye removal at the third cycle