Данила

use Illuminate\Support\Collection;

$collection1 = collect([
    [
        "имя1" => "John",
        "объем1" => "100",
        "мусор" => "x"
    ],
    [
        "имя1" => "Jane",
        "объем1" => "200",
        "мусор" => "y"
    ]
]);

$collection2 = collect([
    [
        "имя2" => "John",
        "объем2" => "300",
        "мусор" => "x"
    ],
    [
        "имя2" => "Jane",
        "объем2" => "400",
        "мусор" => "z"
    ]
]);

function normalizeKeys(Collection $collection, $nameKey, $volumeKey)
{
    return $collection->map(function ($item) use ($nameKey, $volumeKey) {
        return [
            'name' => $item[$nameKey] ?? null,
            'volume' => $item[$volumeKey] ?? null,
        ];
    });
}

$normalized1 = normalizeKeys($collection1, 'имя1', 'объем1');
$normalized2 = normalizeKeys($collection2, 'имя2', 'объем2');

$result = $normalized1->map(function ($item1) use ($normalized2) {
    $match = $normalized2->firstWhere('name', $item1['name']);
    
    return [
        'name' => $item1['name'],
        'volume1' => $item1['volume'],
        'volume2' => $match['volume'] ?? null,
    ];
});